ALBERT

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 353〈/p〉 〈p〉Author(s): Jingzhe Wang, Jianli Ding, Danlin Yu, Xuankai Ma, Zipeng Zhang, Xiangyu Ge, Dexiong Teng, Xiaohang Li, Jing Liang, Ivan Lizaga, Xiangyue Chen, Lin Yuan, Yahui Guo〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Soil salinization is one of the most important causes for land degradation and desertification and is an important threat to land management, farming activities, water quality, and sustainable development in arid and semi-arid areas. Soil salinization is often characterized with significant spatiotemporal dynamics. The salt-affected soil is predominant in the Ebinur Lake region in the Northwestern China. However, detailed local soil salinity information is ambiguous at the best due to limited monitoring techniques. Nowadays, the availability of Multi-Spectral Instrument (MSI) onboard Sentinel-2, offers unprecedented perspectives for the monitoring and mapping of soil salinity. The use of MSI data is an innovative attempt for salinity detection in arid land. We hypothesize that field observations and MSI data and MSI data-derived spectral indices using the partial least square regression (PLSR) approach will yield fairly accurate regional salinity map. Based on electrical conductivity of 1:5 soil:water extract (EC) of 72 ground-truth measurements (out of 116 sample sites) and various spectral parameters, such as satellite band reflectance, published satellite salinity indices, red-edge indices, newly constructed two-band indices, and three-band indices from MSI data, we built a few inversion models in an attempt to produce the regional salinity maps. Different algorithms including Pearson correlation coefficient method (PCC), variable importance in projection (VIP), Gray relational analysis (GRA), and random forest (RF) were applied for variable selection. The results suggest that both the newly proposed normalized difference index (NDI) [(B12 − B7) / (B12 + B7)] and three-band index (TBI4) [(B12 − B3) / (B3 − B11)] show a better correlation with validation data and could be applied to estimate the soil salinity in the Ebinur Lake region. The established models were validated using the remaining 44 independent ground-based measurements. The RF-PLSR model performed the best across the five models with R〈sup〉2〈/sup〉〈sub〉V〈/sub〉, RMSE〈sub〉V〈/sub〉, and RPD of 0.92, 7.58 dS m〈sup〉−1〈/sup〉, and 2.36, respectively. The result from this model was then used to map the soil salinity over the study area. Our analyses suggest that soil salinization changes quite significantly in different seasons. Specifically, soil salinity in the dry season was higher than in the wet season, mostly in the lake area and nearby shores. We contend that the results from the study will be useful for soil salinization monitoring and land reclamation in arid or semi-arid regions outside the current study area.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 353〈/p〉 〈p〉Author(s): Roozbeh Moazenzadeh, Babak Mohammadi〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Root zone temperature is one of the most important soil characteristics, controlling many of the physical, chemical and biological processes in the soil. Temperature varies by soil depth, and exerts a profound impact on plant germination and growth. In this study, the accuracy of two artificial intelligence models including support vector regression (SVR) and elman neural network (ENN) and their hybrids with firefly algorithm (SVR-FA and ENN-FA) and krill herd algorithm (SVR-KHA and ENN-KHA) was assessed in estimating soil temperature (Ts) at 5, 10, 20, 30, 50 and 100 cm depths at Maragheh meteorological station in north-western Iran. The results of the models were evaluated under 5 scenarios with various inputs including the main meteorological parameters measured at the station (air temperature, sunshine hours, relative humidity, wind speed and saturation vapour pressure deficit). Daily Ts data recorded from January 1, 2006 to December 30, 2012 and from January 1, 2013 to December 30, 2015 were used for model training and testing, respectively. The results showed that error rates have decreased from 5 to 10 cm soil depth (root mean square error (RMSE) reduced by 2.97, 4.68 and 3.19% for the best scenarios of SVR, SVR-FA and SVR-KHA models, respectively), whereas error rates have been increasing from 10 to 100 cm soil depths (RMSE increased by 62.4, 80.9 and 73.6% for the best scenarios of SVR, SVR-FA and SVR-KHA models, respectively). For the best scenarios of ENN, ENN-FA and ENN-KHA models, RMSE values decreased by 2.1, 1.6 and 3.1% from 5 to 10 cm depth and increased by 61.1, 84.1 and 81.1% from 10 to 100 cm depth, so that all six models reached their best performance at 10 cm soil depth. Examination of the results in terms of under-estimation or over-estimation of Ts indicated that the lowest and highest differences in performance between under- and over-estimation sets were 0.01 °C (SVR-FA at 5 cm depth) and 1.64 °C (SVR at 100 cm depth) for SVR-based models and 0 °C (ENN at 10 cm depth) and 0.56 °C (ENN at 100 cm depth) for ELM-based models, respectively. According to the results from the best scenarios of SVR, SVR-FA and SVR-KHA models in the under-estimation set at 100 cm depth, all the three models have exhibited a poorer performance over the temperature range 15–25 °C (RMSE increased by 56.7, 47 and 61.3% for SVR, SVR-FA and SVR-KHA, respectively) compared to temperature values outside that range. Exactly the same trend was also observed for ELM-based models, where the mentioned increases in RMSE were about 37.7, 59.4 and 55.5% for ELM, ELM-FA and ELM-KHA, respectively. According to the results, bio-inspired metaheuristic optimisation algorithms based on SVR and ENN which use appropriate meteorological parameters as inputs can have a relatively satisfactory performance in estimating Ts under climatic conditions similar to our study area, especially in lower depths, and can be used as an alternative to direct measurement of this important parameter.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 353〈/p〉 〈p〉Author(s): Lingfei Yu, Yue Chen, Wenjuan Sun, Yao Huang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Globally, excessive grazing is identified as one of the key disturbances leading to grassland degradation and soil carbon (C) loss. Grazing exclusion has been proposed as an effective practice to restore degraded grasslands and to promote C sequestration. However, there is still little knowledge about how soil C changes with grazing exclusion in high-altitude alpine ecosystems with very cold climates. We synthesized data from 63 sites in the literature and 15 sites in a field sampling and investigated the dynamics of soil C stocks following grazing exclusion in alpine grasslands of the Tibetan Plateau. The results showed that the soil C stock increased with grazing exclusion at most sites, with average C sequestration rates of 0.84, 0.58, and 0.49 Mg ha〈sup〉−1〈/sup〉 yr〈sup〉−1〈/sup〉 in the soil layers of 0–10, 10–20, and 20–30 cm, respectively. Based on these results, if 60 million ha of the grasslands on Tibetan Plateau were excluded from grazing livestock by 2020 according to the national plan, then approximately 0.11 Pg C yr〈sup〉−1〈/sup〉 would be sequestered in the soil which equates to about 4.4% of fossil fuel and cement CO〈sub〉2〈/sub〉 emissions in China in 2013. Generally, the rates of soil C increase exhibited a declining pattern with increasing years of grazing exclusion, with a significant decrease occurring after ten years of grazing exclusion. Of the factors examined, the rates of absolute and relative soil C change were both positively related to mean annual precipitation but negatively related to the year of grazing exclusion and initial soil C stock, respectively. The rates of soil C changes increased linearly with those of N change, and no matter how soil C changed (whether it increased or decreased), soil C:N ratios remained stable over the years of grazing exclusion. Our results implied that grazing exclusion is beneficial for soil C sequestration in degraded alpine grassland, especially in humid areas. Moreover, the intrinsic increase in N could keep up with the pace of soil C changes and would sustain soil C sequestration during the recovery process.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 353〈/p〉 〈p〉Author(s): Thomas P. D'Avello, William J. Waltman, Sharon W. Waltman, James A. Thompson, Joseph Brennan〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We examine the climatic record of the conterminous United States from 1895 to 2014 as expressed through the PRISM dataset and the jNewhall model. Specifically, the zero line of the Annual Water Balance (AWB) and the respective oscillation zone through its longitudinal extent is examined. The zero line corresponds to the Pedocal/Pedalfer line defined by C.F. Marbut, considered outdated in current pedological circles, but conceptually powerful in denoting regional negative vs. positive AWB. Soil Moisture Regimes are reviewed and a means of expressing Soil Moisture Regime variability is introduced. Results indicate a difference in the width of the AWB oscillation zone from South to North with a demarcation approximating 40 degrees North Latitude. PRISM data is verified from a select set of National Weather Service station data to assess the utility of using readily accessible PRISM data for performing similar work by others. The effect of climate variables on organic carbon (OC) stock and depth of maximum Calcium Carbonate concentration is examined for a suite of soils along a climo-sequence from North Dakota to Central Iowa and found to account for a mild amount of the variability of both variables.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 353〈/p〉 〈p〉Author(s): Zengming Chen, Yehong Xu, Daniela F. Cusack, Michael J. Castellano, Weixin Ding〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Nitrogen (N) input rapidly increases available N in natural and managed ecosystems, potentially altering key ecosystem processes like decomposition. The effect of N enrichment on decomposition rates may be affected by the chemical quality of organic matter (OM), and the extent of N increment. Manure decomposition is an important process in agricultural systems, releasing nutrients and contributing to carbon (C) cycling. However, its response to N fertilization is poorly understood. To help address this knowledge gap, we decomposed pig manure (PM) and chicken manure (CM) under two rates of N fertilization (N1, 75 kg N ha〈sup〉−1〈/sup〉; N2, 112.5 kg N ha〈sup〉−1〈/sup〉) in a cropland in northeast China. We used litterbags to determine the dynamics of manure decomposition, while monitoring changes in the molecular composition with solid-state 〈sup〉13〈/sup〉C nuclear magnetic resonance (NMR) spectroscopy. After one-year, the decomposition rate of PM was significantly greater than CM (0.516 vs. 0.483 year〈sup〉−1〈/sup〉). Spectra of 〈sup〉13〈/sup〉C NMR indicated that PM initially contained more 〈em〉O〈/em〉-alkyl C and di-〈em〉O〈/em〉-alkyl C (representing cellulose). In contrast, the contents of alkyl C (representing lipids) and aromatic C (representing lignin) were less in PM than CM, such that PM was overall more easily degradable. There was no N rate effect on CM decomposition. However, the decomposition rate of PM was significantly lower under high N than low N (0.410 vs. 0.622 year〈sup〉−1〈/sup〉), apparently related to suppressed degradation of 〈em〉O〈/em〉-alkyl C and di-〈em〉O〈/em〉-alkyl C. This result was surprising, since N enrichment is generally expected to promote degradation of more labile compounds like cellulose. At the same time, the loss of syringyl monomer of lignin in PM was reduced by high N fertilization. Together, these results suggest that decreased losses of 〈em〉O〈/em〉-alkyl C and di-〈em〉O〈/em〉-alkyl C may have resulted from physical association of cellulose with more resistant lignin compounds. Net N mineralization was observed from manure decomposition and was greater for CM than PM, and high N fertilization suppressed N release from PM. Overall, our findings suggest that high rate of N fertilization may slow the decomposition of otherwise labile manure, potentially promoting greater C retention in soils.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 352〈/p〉 〈p〉Author(s): Sibylle Faust, Heinz-Josef Koch, Rainer Georg Joergensen〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Undisturbed soils columns were transplanted from three tillage treatments at four sites in Central Germany to one site to investigate the relations between the CO〈sub〉2〈/sub〉 efflux, soil temperature (T〈sub〉S〈/sub〉) and volumetric water content (VWC) over one year in an unplanted period and maize (〈em〉Zea mays〈/em〉 L.) planted period. No tillage and grubber, i.e. rigid‑tine cultivator, (10-15 cm) systems contain higher stocks of microbial biomass C (MBC) in comparison with mouldboard ploughing (25-30 cm). This must be due to a reduction in microbial turnover, because higher VWC reduces T〈sub〉S〈/sub〉. At 5 cm depth, VWC was lowest with plough tillage throughout the year. At 15 cm depth, VWC was highest with grubber tillage during the planted period. During the unplanted period, mean T〈sub〉S〈/sub〉 was generally highest with grubber tillage. During the planted period, mean difference in T〈sub〉S〈/sub〉 increased in the order no tillage 〈 plough 〈 grubber at 5 cm depth and in the order plough 〈 grubber 〈 no-tillage at 15 cm depth. Mean CO〈sub〉2〈/sub〉 efflux was 1.12 t C ha〈sup〉−1〈/sup〉 in the unplanted and 2.85 t C ha〈sup〉−1〈/sup〉 in the planted period. Multiple linear relationships showed that T〈sub〉S〈/sub〉 and VWC explained 70.4% of the variance in CO〈sub〉2〈/sub〉 evolution rates in the unplanted and 37.2% in the planted period. T〈sub〉S〈/sub〉 effects generally dominated and showed similar regression coefficients in both periods. VWC had smaller effects, which were positive in the unplanted period and negative in the planted period. Significant tillage × T〈sub〉S〈/sub〉 interactions were observed in the unplanted period and tillage × VWC interactions in the planted period. Interactions were caused by strong positive T〈sub〉S〈/sub〉 effects with grubber tillage in the unplanted period and by strong negative VWC effects with plough tillage in the planted period. From a soil ecological viewpoint, grubber and no tillage can be recommended, as it improves microbial life conditions.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 353〈/p〉 〈p〉Author(s): Shangqi Xu, Xia Liu, Xiujun Li, Chunjie Tian〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Wetland restoration has been conducted worldwide due to the important ecological functions provided by wetlands. However, the global patterns of soil organic carbon (SOC) change following wetland restoration are not clear, which has limited the efficacy of the management of restored wetlands. In this study, we synthesized the results from 41 studies and carried out a meta-analysis to examine the SOC dynamics following wetland restoration and the underlying mechanisms. The SOC of restored wetlands was 13.8% (〈em〉p〈/em〉 = 0.017) higher than that of cultivated wetlands and 29.2% (〈em〉p〈/em〉 〈 0.001) lower than that of natural wetlands. Wetland restoration facilitated SOC sequestration under certain conditions, including when the wetlands were restored via water supplementation, had seasonal hydrology in their natural status (before cultivation), were peatlands, occurred under a temperate climate, were restored for 6 to 10 years, or had been cultivated no longer than 15 years before restoration. Meanwhile, some conditions had negative effects on SOC sequestration, including wetlands under a tropical climate, those restored using a plantation approach, and those with a tidal hydrology after restoration. Model selection analysis suggested that the hydrological conditions of cultivated wetlands, soil depth, vegetation type, peat condition and restored age were important influential factors affecting SOC after wetland restoration, with the first 2 being the most important influential factors. Our results indicate that wetland restoration is inefficient in terms of SOC recovery and that wetland restoration to recover SOC is urgently needed and should be conducted more appropriately. The results of this study provide theoretical support for wetland management with the aim of SOC sequestration.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 353〈/p〉 〈p〉Author(s): Xiaoting Xie, Yili Lu, Tusheng Ren, Robert Horton〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Information on soil thermal properties is needed for estimating soil temperature (〈em〉T〈/em〉) and heat flux. However, few datasets are available for assessing the effects of soil thermal diffusivity (κ) parameterization on diurnal 〈em〉T〈/em〉 estimations. In this study, three κ parameterization methods, all based on soil physical properties, are compared for determining the responses of 〈em〉Τ〈/em〉 estimation to κ on two field soils. Among the three methods, two are the combination of the de Vries heat capacity model with either the McCumber and Pielke thermal conductivity model (MP-D) or the Johansen thermal conductivity model (J75-D), and the other one is the Xie et al. κ model (X18). The harmonic approach was used to estimate 〈em〉T〈/em〉 in the 0- to 5-cm layer on a sandy loam soil, and in the 5- to 10-cm layer on a silty clay loam soil from the measured 〈em〉T〈/em〉 data at a single depth. The J75-D and X18 methods produced close κ values, while the κ values from the MP-D method deviated significantly from that of other models. The 〈em〉T〈/em〉 results from the J75-D and X18 based harmonic methods agreed well with 〈em〉T〈/em〉 measurements. On the sandy loam soil, 〈em〉T〈/em〉 estimates from the MP-D method had a RMSE (root mean square error) of 3.04 °C and an RSR (ratio of RMSE to the standard deviation of the observations) of 0.53, while smaller RMSE and RSR values were obtained from the X18 method (1 °C and 0.17) and J75-D method (0.8 °C and 0.14). For the silty clay loam soil, the RMSE and RSR of 〈em〉T〈/em〉 estimates from the MP-D-based harmonic method were 0.82 °C and 0.27, respectively, which were larger than those (0.57 °C and 0.19) of the X18 and J75-D-based harmonic method. We concluded that the X18 and J75-D based harmonic methods could provide more accurate soil profile 〈em〉Τ〈/em〉 estimates than the MP-D method.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 353〈/p〉 〈p〉Author(s): Thiago Leite de Alencar, Arilene Franklin Chaves, Alcione Guimarães Freire, Ícaro Vasconcelos do Nascimento, Alexandre dos Santos Queiroz, Jaedson Cláudio Anunciato Mota〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Field capacity (FC) is one of the most cited soil physical parameters and is relevant for the management of agricultural systems. In the search for alternatives to the estimation of FC, several researchers have proposed methods based on dynamic and static criteria. Evaluating these methods within a range of soil textural classes is important for prospects of their uses with higher water use efficiency. Based on the hypothesis that FC for a certain soil textural class is exclusively associated with an equivalent pore diameter, 〈em〉D〈/em〉-〈em〉threshold〈/em〉, which separates structural and textural porosity, and that textural pores define the FC conditions, this study aimed to: 1) estimate the equivalent pore diameter (〈em〉D〈/em〉-〈em〉threshold〈/em〉) which defines FC in each soil textural class in situ and, with the change of density, from the alterations in its water characteristic curve - WCC; 2) estimate the water content at FC in each soil textural class in situ and, with the change of density, from the alterations in its WCC. To obtain the water content corresponding to FC in situ, instantaneous profile-type experiments were conducted in five soil textural classes. To estimate FC and 〈em〉D〈/em〉-〈em〉threshold〈/em〉 based on the change in pore volume (CPV), soil water characteristic curves were used considering two situations: before and after compaction. Correlation and regression analyses were carried out between 〈em〉D〈/em〉-〈em〉threshold〈/em〉 and sand percentage, between water content at FC and the fitting parameters α and 〈em〉n〈/em〉 of the model of van Genuchten (1980), and between the value of the tangent at the inflection point of the soil WCC and the parameter α. By comparing 〈em〉D〈/em〉-〈em〉threshold〈/em〉 values obtained by the field and CPV methods, it was possible to observe that for the range of textural classes analyzed, in general, 〈em〉D〈/em〉-〈em〉threshold〈/em〉 values obtained by CPV were different from those obtained in situ. Therefore, the methodological procedure CPV does not represent the actual 〈em〉D〈/em〉-〈em〉threshold〈/em〉 of the FC found under field conditions. The values of water content corresponding to FC obtained by the CPV protocol are not due to the physical aspect conceived in the method's proposal. Thus, since these values were not due to the 〈em〉D〈/em〉-〈em〉threshold〈/em〉, this protocol cannot be indicated because it became evident that there was no clear cause-effect relationship. It was concluded that: 1) the principle of the method of estimating FC must be consistent with processes occurring in the soil. Since FC is dependent on soil processes, and associated with a drainage rate, there is no good reason why the CPV method correctly estimates the attribute; 2) the water content at FC in a certain soil textural class is not exclusively associated with only one equivalent pore diameter, 〈em〉D〈/em〉-〈em〉threshold〈/em〉, so the hypothesis assumed in the study has not been confirmed; and 3) protocols based on soil water dynamics should preferentially be used to estimate FC, to the detriment of methods based on static criteria.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 353〈/p〉 〈p〉Author(s): Yanan Huang, Jaivime Evaristo, Zhi Li〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Interpretation of groundwater recharge mechanisms is problematic because of the muted instantaneous response of subsurface water to rainfall and limited recharge rates, particularly in semi-arid environments with deep loess deposits. Here we identify the possible groundwater recharge mechanisms in 200-m thick loess deposits with unsaturated zone thickness of over 40 m. We collected soil samples up to 15 m deep under four land use types (one grassland and three apple orchards with stand ages 15, 24 and 30 years old), and used three-year precipitation and groundwater samples to determine the contents of stable water isotopes, chloride, and tritium. Our overarching goal is to determine the relative importance of piston and preferential flow in groundwater recharge using multiple tracers and quantify the effects of land use change on groundwater recharge. We find that while both piston and preferential flows are important in groundwater recharge, the unsaturated and saturated zones have yet to come to hydraulic equilibrium. This suggests different groundwater recharge mechanisms: tracers in the unsaturated zone suggest piston flow, while the detectable tritium in the saturated zone implies preferential flow. Recharge rates in the unsaturated zones range between 23 and 82 mm year〈sup〉−1〈/sup〉, accounting for 4%–14% of mean annual precipitation, and increasing with depth presumably because of land use and/or climatic conditions. Total recharge rate in the saturated zone is 112.6 ± 44.1 mm year〈sup〉−1〈/sup〉, accounting for 19 ± 9% of mean annual precipitation. Overall, our study finds that piston flow contributes more to total recharge (53%–69%) than does preferential flow. Nevertheless, piston flow may become less important because of land use change (farmland to apple orchard conversion). Our findings have implications for the need to strike a delicate balance between the economic gains from afforestation and the possible risks to groundwater supply sustainability.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 353〈/p〉 〈p〉Author(s): Lei Deng, Changhui Peng, Chunbo Huang, Kaibo Wang, Qiuyu Liu, Yulin Liu, Xuying Hai, Zhouping Shangguan〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Soil extracellular enzymatic activity (EEA) stoichiometry could reflect the biogeochemical equilibrium between the metabolic requirements of microbial communities and environmental nutrients availability. However, the drivers of soil microbial metabolic limitation (SMML) changes remain poorly understood following vegetation restoration. We compared sites along a vegetation restoration chronosequence over a 30-year period on the Loess Plateau, China, and measured the potential activities of two C-acquiring enzymes (β-1,4-glucosidase (BG) and β-〈span〉d〈/span〉-cellobiosidase (CBH)), two N-acquiring enzymes (β-1,4-〈em〉N〈/em〉-acetylglucosaminidase (NAG) and 〈span〉l〈/span〉-leucine aminopeptidase (LAP)), and one organic-P-acquiring enzyme (alkaline phosphatase (AP)), to quantify and compare the variations in metabolic limitations for soil microorganisms using EEA stoichiometry. The results showed constant microbial P limitation, but not N limitation, and an open downward “unimodal” trend in microbial C limitation; however, the microbial P limitation displayed exactly the opposite trend during vegetation restoration. Restoration age and properties of plant, soil, and microorganisms contributed to 82.9% of microbial C limitation and 84.6% of microbial P limitation, with soil presenting the highest relative effects of 76.1% and 59.6% on microbial C and P limitations, respectively. Plant productivity and species diversity decreased microbial C limitation owing to increasing plant C inputs, but increased microbial P limitation owing to plant nutrients competition with soil microorganisms. When the fungi:bacteria ratio in the soil increased, the SMML increased. Vegetation restoration increased the soil nutrients content and reduced SMML, and a decrease in the soil water content increased microbial P limitation. Thus, the effects of long-term vegetation restoration on SMML were the result of combined influences of plants, soil, and microorganisms.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 353〈/p〉 〈p〉Author(s): Cancan Zhao, Jie Zhao, Jianping Wu, Aimée T. Classen, Yanxia Li, Yiping Lou, Weixin Zhang, Xin Jing, Yuanhu Shao, Shenglei Fu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Bamboos are widespread in the subtropics and tropics. They grow quickly, and are therefore important substitute for timber. Bamboo forest management and cultivation often include removing competitive trees; thus these shifts in forest composition should cascade to impact soil communities and the processes they mediate. Using a long-term (12 year) bamboo forest management study, we determined the impact of bamboo forest management on soil microbial and nematode community composition through time (2008–2010). Surprisingly, we found that conversion from a mixed and relatively diverse bamboo forest to a pure bamboo forest did not affect bamboo biomass. However, the soil fungal:bacterial ratio, nematode diversity index, and fungivores:bacterivores all declined within and across years. Taken together, our results suggest that conversion from mixed to pure bamboo forest can cause a switch from the fungal-based to the bacterial-based energy channel, i.e., accelerate the energy flow and reduce the stability of the soil ecosystem. The findings suggest that managing for a mixed bamboo forest may increase forest diversity and health overtime.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 355〈/p〉 〈p〉Author(s): Alexandre M.J-C. Wadoux, Dick J. Brus, Gerard B.M. Heuvelink〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Machine learning techniques are widely employed to generate digital soil maps. The map accuracy is partly determined by the number and spatial locations of the measurements used to calibrate the machine learning model. However, determining the optimal sampling design for mapping with machine learning techniques has not yet been considered in detail in digital soil mapping studies. In this paper, we investigate sampling design optimization for soil mapping with random forest. A design is optimized using spatial simulated annealing by minimizing the mean squared prediction error (MSE). We applied this approach to mapping soil organic carbon for a part of Europe using subsamples of the LUCAS dataset. The optimized subsamples are used as input for the random forest machine learning model, using a large set of readily available environmental data as covariates. We also predicted the same soil property using subsamples selected by simple random sampling, conditioned Latin Hypercube sampling (cLHS), spatial coverage sampling and feature space coverage sampling. Distributions of the estimated population MSEs are obtained through repeated random splitting of the LUCAS dataset, serving as the population of interest, into subsets used for validation, testing and selection of calibration samples, and repeated selection of calibration samples with the various sampling designs. The differences between the medians of the MSE distributions were tested for significance using the non-parametric Mann-Whitney test. The process was repeated for different sample sizes. We also analyzed the spread of the optimized designs in both geographic and feature space to reveal their characteristics. Results show that optimization of the sampling design by minimizing the MSE is worthwhile for small sample sizes. However, an important disadvantage of sampling design optimization using MSE is that it requires known values of the soil property at all locations and as a consequence is only feasible for subsampling an existing dataset. For larger sample sizes, the effect of using an MSE optimized design diminishes. In this case, we recommend to use a sample spread uniformly in the feature (i.e. covariate) space of the most important random forest covariates. The results also show that for our case study, cLHS sampling performs worse than the other sampling designs for mapping with random forest. We stress that comparison of sampling designs for calibration by splitting the data just once is very sensitive to the data split that one happens to use if the validation set is small.〈/p〉〈/div〉

Description: 〈p〉Publication date: 15 December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 356〈/p〉 〈p〉Author(s): Mark A. Chappell, Jennifer M. Seiter, Haley M. West, Lesley F. Miller, Maria E. Negrete, Joshua J. LeMonte, Beth E. Porter, Cynthia L. Price, Matthew A. Middleton〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Soil heterogeneity is a major contributor to the uncertainty in predicting the environmental fate of data-scare contaminants. For this paper, we focused on research designed to predict the soil environmental fate of the new munition compound, called 2,4-dinitroanisole (DNAN) -a compound increasingly employed by the U.S. and international militaries in the next-generation, insensitive explosive formulations. Here, we employed multivariate statistical correlation models to predict DNAN sorption among different soil “types” seeking to reduce the uncertainty common in all contaminant sorption models by using soil taxonomic designation as a calibrant. We collected composite soils classified under the Ultisols taxonomic Order in the U.S. National Resource Conservation Service soil classification system and quantified their properties via physical and chemical characterizations. Using multivariate statistical modeling modified for compositional data analysis (CoDa), we developed quantitative analogies of the Ultisols by partitioning the characterization data up into four different compositions: Water-extracted, Mehlich-III (referring to the weak acid) extracted, particle-size distribution, and solid-phase carbon‑nitrogen‑sulfur compositions. DNAN sorption was measured in batch soil suspensions and distribution coefficients (K〈sub〉D〈/sub〉) were calculated using linear regression modeling. Prediction models testing the correlation of the DNAN K〈sub〉D〈/sub〉 values to the centered logratio -transformed compositions were calculated using CoDa-modified multilinear regression. Results showed that DNAN sorption was only predictable by dissolved organic carbon, pH, and the exchangeable cations Ca and K within the water-extracted composition. Analogies for DNAN sorption were the most discriminating at the Suborder level because of the inherent ambiguity in the Hapludults class at the Great Group level.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0016706119303842-ga1.jpg" width="375" alt="Unlabelled Image" title="Unlabelled Image"〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 356〈/p〉 〈p〉Author(s): Jörg Prietzel, Martin Wiesmeier〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A correct quantification of soil surface and soil organic carbon (SOC) stocks is crucial for the evaluation of important soil functions, including atmospheric C sequestration. At present, soil science lacks (i) a clear definition of soil depth, (ii) consented procedures for soil sampling, as well as (iii) adequate awareness concerning pitfalls and caveats associated with quantification of soil surface area and large-scale SOC stocks in mountainous, complex landscapes. Traditional SOC stock quantification in these landscapes often did not adequately address site-specific geomorphological conditions and thus yielded incorrect results due to combination of incompatible methods for soil depth assessment, soil profile or core sampling, and soil surface area calculation. In our paper, we suggest unequivocal definitions of soil depth, horizon thickness, and SOC density, which can be applied for soils in sloping as well as flat terrain. Moreover, we quantify and discuss potential SOC (and other soil nutrient) stock assessment errors in mountainous regions, using the German Alps as case study. We present a protocol to ensure an unbiased quantification of soil surface area, as well as SOC or nutrient element stocks in mountainous landscapes. Taking into account the considerable area of sloping terrain on the global scale, and particularly in mountainous countries (e.g. Switzerland, Austria, Andes Countries, Nepal, Japan), our publication will contribute to a more accurate quantification of soil stocks of SOC and important nutrients as well as area-based C fluxes (e.g. CO〈sub〉2〈/sub〉 sequestration or release) or other surface-related biogeochemical fluxes.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0016706119308018-ga1.jpg" width="488" alt="Unlabelled Image" title="Unlabelled Image"〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 356〈/p〉 〈p〉Author(s): S.S. Paul, N.C. Coops, M.S. Johnson, M. Krzic, S.M. Smukler〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The performance of digital soil mapping (DSM) model is highly reliant on the intensity and spatial distribution of the input soil data points. Increasing the number of soil data points (i.e. samples) improves the accuracy of the prediction, but it also raises the sampling effort, including the time, money and labor required for field and laboratory analysis. Thus, optimizing the production of DSMs requires maximizing accuracy while minimizing cost. In this study, we evaluated a range of strategies for DSM of a farm field using high spatial resolution ancillary environmental data (e.g. unmanned aerial vehicle-UAV imagery) and compared sampling efforts of soil data generated from standard laboratory analysis (SLA) and mid-infrared spectroscopy (MIRS) at equivalent costs. We produced DSMs of a number of soil properties including sand, silt, clay, pH, salinity, organic matter, and total nitrogen. We employed Conditioned Latin Hypercube Sampling (cLHS) to generate a range of sampling efforts from the full SLA (〈em〉n〈/em〉 = 62) and MIRS (〈em〉n〈/em〉 = 308) datasets and contrasted the DSM outcomes modeled using kriging with external drift (KED). We found that the DSM outputs were most effective, in terms of accuracy and cost, at 50–60% of the full sampling effort. Although MIRS predictions of soil properties introduced a sizable amount of error, DSMs produced using the MIRS dataset were more accurate as compared to the outcomes of SLA datasets at equivalent sampling efforts. The prediction accuracy for DSMs varied across the soil properties with R〈sup〉2〈/sup〉 ranging from 0.82 (for sand) to 0.45 (for total nitrogen) at the optimum sampling effort. The outcomes of the study highlight that spatially optimized sampling efforts and the use of the MIRS technique substantially improve the cost efficiency and accuracy of kriging-based DSM models for predicting a range of field scale soil properties.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 356〈/p〉 〈p〉Author(s): Nader Shahabinejad, Majid Mahmoodabadi, Ahmad Jalalian, Elham Chavoshi〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Soil particle size distribution (PSD) plays an important role in wind erosion studies and sediment transport modeling. Few studies have been done focusing on the susceptibility of different soil fractions to wind erosion under natural conditions. This study was performed to measure in-situ wind erosion rates using a portable wind tunnel facility on 60 undisturbed soils of arid to semiarid regions. The effects of primary (i.e. clay, silt, and sand particles) and 16 secondary (aggregate) size classes were attributed to wind erosion rates. Moreover, the boundaries between major fractions of the soils (i.e. micro-aggregates, meso-aggregates and macro-aggregates) were determined. The result showed that clay and silt particles and also surface rock fragment were inversely proportional to wind erosion rates as power functions, whereas sand content showed a positive exponential relationship. The size ranges of 〈53 μm, 53–300 μm and 〉300 μm were distinguished for the micro-aggregates, meso-aggregates, and macro-aggregates, respectively. The meso-aggregate fraction was proportional and the micro-aggregate and macro-aggregate fractions were inversely proportional to wind erosion rates. Furthermore, a narrower size range of 75–150 μm was detected as the most erodible soil fraction. The distribution of the primary particles in the major aggregate fractions was different, so that in the meso-aggregates, sand particles and in the micro-aggregates and macro-aggregates, silt and especially clay particles predominated. It is concluded that the presence of macro-aggregates (〉300 μm) associated with fine primary particles (clay) can significantly reduce wind erosion rate rather than the sandy soils containing weaker aggregates.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 355〈/p〉 〈p〉Author(s): A. Schomburg, D. Sebag, P. Turberg, E.P. Verrecchia, C. Guenat, P. Brunner, T. Adatte, R. Schlaepfer, R.C. Le Bayon〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Soil structure formation in alluvial soils is a fundamental process in near-natural floodplains. A stable soil structure is essential for many ecosystem services and helps to prevent river bank erosion. Plants and earthworms are successful soil engineering organisms that improve the soil structural stability through the incorporation of mineral and organic matter into soil aggregates. However, the heterogeneous succession of different textured mineral and buried organic matter layers could impede the development of a stable soil structure. Our study aims at improving the current understanding of soil structure formation and organic matter dynamics in near natural alluvial soils. We investigate the effects of soil engineering organisms, the composition, and the superimposition of different alluvial deposits on the structuration patterns, the aggregate stability, and organic matter dynamics in 〈em〉in vitro〈/em〉 soil columns, representing sediment deposition processes in alluvial soils. Two successions of three different deposits, silt–buried litter–sand, and the inverse, were set up in mesocosms and allocated to four different treatments, i.e. plants, earthworms, plants + earthworms, and a control. X-ray computed tomography was used to identify structuration patterns generated by ecosystem engineers, i.e. plant root galleries and earthworm tunnels. Organic matter dynamics in macro-aggregates were investigated by Rock-Eval pyrolysis. Plant roots only extended in the top layers, whereas earthworms preferentially selected the buried litter and the silt layers. Soil structural stability measured via water stable aggregates (%WSA) increased in the presence of plants and in aggregates recovered from the buried litter layer. Organic matter dynamics were controlled by a complex interplay between the type of engineer, the composition (silt, sand, buried litter) and the succession of the deposits in the mesocosm. Our results indicate that the progress and efficiency of soil structure formation in alluvial soils strongly depends on the textural sequences of alluvial deposits.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 355〈/p〉 〈p〉Author(s): F.J.T. van der Bom, T.I. McLaren, A.L. Doolette, J. Magid, E. Frossard, A. Oberson, L.S. Jensen〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉Data on the dynamics and fate of phosphorus (P) under low soil-test P (STP) conditions is essential for the development of cropping strategies with a high P use efficiency. This study examined the effects of long-term (20 years) mineral and organic fertiliser P applications on a P-depleted sandy loam soil in Denmark. The cycling of P was examined by use of P budgets (inputs-offtake), chemical P extractions, 〈sup〉33〈/sup〉P isotopic exchange kinetics (IEK), and solution 〈sup〉31〈/sup〉P nuclear magnetic resonance (NMR) spectroscopy on NaOH-EDTA extracts.〈/p〉 〈p〉Recovery of applied P in the topsoil was smaller for animal slurry P compared with mineral fertiliser P. The budgets suggest deeper soil layers play an important role for the cycling of P. Resin-extractable P (2 to 17 mg kg〈sup〉−1〈/sup〉), Olsen-P (7 to 16 mg kg〈sup〉−1〈/sup〉) and E〈sub〉1min〈/sub〉 (1 to 6 mg kg〈sup〉−1〈/sup〉) were correlated with the P budgets. Between 63 and 77% of total inorganic P was not exchangeable in a period of three months (E〈sub〉〉3months〈/sub〉), with the lowest value observed in no-P treatment N〈sub〉1〈/sub〉K〈sub〉1〈/sub〉. The data show that a redistribution of exchangeable P had taken place under the influence of a strongly negative P budget. Microbial P (6 to 18 mg kg〈sup〉−1〈/sup〉) increased under animal slurry inputs compared with mineral fertiliser applications (〈em〉p〈/em〉 〈 0.05). All soils were dominated by phosphomonoesters and orthophosphate (98 to 99% of the NMR signal). Concentrations of orthophosphate (86 to 135 mg kg〈sup〉−1〈/sup〉) varied significantly between treatments (〈em〉p〈/em〉 〈 0.01), whereas forms of organic P remained largely unchanged.〈/p〉 〈p〉The results demonstrate that P applications increased the amount of P that is potentially available for plants, irrespective of input form. Nevertheless, most P applied in excess of crop uptake resulted in an increase of the amount of P that is slowly exchangeable. Under low soil test P conditions such as in the current trial, fertiliser P applied in excess of plant demand that accumulates in soil would thus only be partially available for crops in subsequent years. On the other hand the data suggests that soil P reserves may be utilised for crop growth, but at the low soil P intensity plant access to P will have to be managed carefully.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 354〈/p〉 〈p〉Author(s): Vanessa Pino, Alex McBratney, Mario Fajardo, Neil Wilson, Rosalind Deaker〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The patterns of soil biodiversity across different soil gradients still require evaluation in different environments. A close relationship between soil biodiversity and soil physicochemical properties (e.g. soil pH) is evident in most studies, but a large unexplained residual variance is usually reported. This suggests that a deeper exploration into the multidimensional nature of these biotic-abiotic interactions will help develop our understanding of how a combination of soil properties drives soil biodiversity more than any one soil attribute. This was tested by analysing the multivariate associations between soil microbial diversity and soil physicochemical heterogeneity across different Australian soil landscapes. The study area involved two orthogonal transects each of ~1000 km across the state of New South Wales (NSW). A set of 33 abiotic attributes including soil properties and other key environmental covariates were correlated against a soil microbial DNA dataset (16S rRNA and ITS genes) to profile the soil bio-physicochemical relationships. This was undertaken for two land use archetypes representing natural and managed ecosystems. The study found that soil microbial communities were highly related to multiple soil attributes and vegetation. Even though the extent of these relationships varied depending on the environmental scenario and the structural microbial community component analysed, the multidimensional association with soil heterogeneity was evident beyond any single soil property, environmental gradient or land use.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 353〈/p〉 〈p〉Author(s): 〈/p〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 354〈/p〉 〈p〉Author(s): Irina Kurganova, Agustin Merino, Valentin Lopes de Gerenyu, Nieves Barros, Olga Kalinina, Luise Giani, Yakov Kuzyakov〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Abandonment of croplands ongoing on 220 million ha worldwide contributes strongly to soil restoration by improvement of degraded properties and medium- and long-term carbon (C) sequestration in post-agricultural ecosystems. Two interrelated processes – decomposition and stabilization of soil organic carbon (SOC) – govern SOC dynamics and affect the C source or sink functions of former croplands. We investigated how the abandonment of arable soils affects (i) accumulation of SOC, its composition, stability, and turnover during the post-agricultural restoration of soils, and (ii) microbial activity parameters. A chronosequence study was carried in two bioclimatic zones of European Russia: deciduous forest (〈em〉Luvic Phaeozems〈/em〉, PH-chronosequence) and dry steppe (〈em〉Calcic Chernozems〈/em〉, CH-chronosequence). Each chronosequence included an arable soil, 3–4 soils abandoned at increasing time periods (up to 35 years), and natural soil: never cropped Phaeozem and completely restored Chernozem. We combined the results of nuclear magnetic resonance (NMR), thermal analysis including Differential Scanning Calorimetry and Derivative Thermogravimetry, long-term incubation for SOC mineralization, and microbiological activity (basal respiration and microbial C content). Degraded Phaeozems with low SOC amount had much higher relative increase in SOC content (134%) during the post-agricultural restoration compared to SOC-rich Chernozems (38%). SOC gains were recorded in all organic compound classes identified by NMR and thermal analysis, but the increase of recalcitrant SOC was more pronounced in the post-agricultural Chernozems than in the Phaeozems. The post-agricultural Chernozems were characterized by higher SOC aliphaticity and aromaticity than Phaeozems. Microbial activity and biodegradable SOC increased gradually during post-agricultural restoration. Being mostly a function of climate and vegetation, the soil type was the primary factor explaining the greatest portion (54–88%) of the total variance for most soil and microbial parameters. Concluding, despite SOC content increased in both Chernozems and Phaeozems during the post-agricultural restoration, the mechanisms of C sequestration and stabilization were dependent on climate, vegetation, and on the degradation intensity during the agricultural use. The accumulation of organic compounds was specific for virgin soils dominating in deciduous forest and steppes, and had direct consequences for microbial activities, C turnover and sequestration.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0016706118319086-ga1.jpg" width="500" alt="Unlabelled Image" title="Unlabelled Image"〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 354〈/p〉 〈p〉Author(s): Yujie Zhou, Zhenyi Jia, Junxiao Wang, Lian Chen, Mengmeng Zou, Yan Li, Shenglu Zhou〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉To study the heavy metal contamination and its transfer patterns in a wheat-rice rotation system in Dingshu, a typical industry county in China, 52 pairs of complete crop samples and corresponding soil samples (0–20 cm) were collected from this area. All samples were detected for the total concentrations of six heavy metals. Available factions and main soil properties were also analyzed. The results showed that Cd, Ni, Pb and Zn in both soil had moderate accumulation and these elements in corresponding grains exceeded their standard values to some extent. Most of these metals had higher concentrations in the eastern and central regions in both crop grains and the corresponding soils, which were related to the strong human activities in this region. In particular, the distribution of Cd in both soils and crops exhibited the most significant spatial correlation, whereas Cr had opposite trends. These elements in wheat and rice grains was related to different influencing factors and varied with different heavy metals. Cross-correlograms further quantitated the spatial influencing factors of elements in soils and various organs on crop gains. Cd prediction models for rice and wheat grains were stimulated based on nonedible organs and soil properties with a maximum 〈em〉r〈/em〉〈sup〉2〈/sup〉 of 0.748. These models are helpful to predict Cd accumulation in grains within wheat-rice rotation systems and thus allow farmers to reduce threats of heavy metals by adopting certain agronomic practices in different periods.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 355〈/p〉 〈p〉Author(s): Xiaolei Huang, Zhixin Jia, Junjie Guo, Tingliang Li, Dasheng Sun, Huisheng Meng, Guanghui Yu, Xinhua He, Wei Ran, Shusheng Zhang, Jianping Hong, Qirong Shen〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Soils play a vital role in the global carbon (C) cycle, yet little is known about the calcium (Ca)-mediated stabilization of soil organic carbon (SOC) in calcareous soils. With wet sieving, density fractionation and an incubation experiment from field soils, we investigated the effects of long-term fertilization on the Ca-mediated stabilization of aggregate-associated organic C and on the SOC stock at a soil depth of 0–20 cm in a reclaimed Cambisol on the Loess Plateau of China. Compared to the initial soil, after ten years the SOC stock increased by 50%, 76%, 94% and 110% in soils amended with no fertilizer (control), 100% chemical fertilizer, 50% chemical fertilizer plus 50% chicken manure compost and 100% chicken manure compost, respectively. The specific C mineralization rate (SCMR, rate per unit SOC) decreased as silt and clay 〉 macroaggregate 〉 microaggregate, indicating that SOC in microaggregates was more stable than in macroaggregates and the silt and clay fraction. The exchangeable Ca in the bulk soil (〈em〉P〈/em〉 〈 0.001) and soil aggregates (〈em〉P〈/em〉 〈 0.001) were positively correlated with the SOC, whereas the Ca carbonate (CaCO〈sub〉3〈/sub〉) was negatively correlated with the SCMR (〈em〉P〈/em〉 〈 0.001). The application of compost not only increased the exogenous C inputs but also promoted the transformation of CaCO〈sub〉3〈/sub〉 to exchangeable Ca compared with the sole chemical fertilization. Furthermore, organic fertilization significantly increased the organic C in the heavy fraction (〉 2.0 g cm〈sup〉−〈/sup〉〈sup〉3〈/sup〉) compared with the sole chemical fertilization, which was positively correlated with the mass proportion of macroaggregates (〈em〉P〈/em〉 〈 0.001). These results indicate that organic fertilization can enhance the availability of Ca for C binding possibly by forming organo-Ca complexes, which in turn improve soil aggregation, and thus contribute to a long-term SOC sequestration in reclaimed soils of the Loess Plateau of China.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 355〈/p〉 〈p〉Author(s): Steffen A. Schweizer, Franziska B. Bucka, Markus Graf-Rosenfellner, Ingrid Kögel-Knabner〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Aggregation assembles different size mixtures of soil particles into a larger architecture. Such mixtures impede resolving which particles build aggregates and how these control the accumulation of soil organic matter (OM). Here we present an approach to differentiate the size distributions of soil fractions in the size range of microaggregates (〈250 μm) from their dispersible particle-size distribution using dynamic image analysis. This approach enabled us to differentiate the magnitude and preferential size ranges of aggregates and non-aggregated particles. Wet sieving was used to isolate free microaggregate-sized fractions. Larger soil structures 〉250 μm were sonicated to isolate occluded size fractions 〈250 μm. To investigate the impact of soil texture, we analyzed topsoil samples of an arable site on Cambisol soils with a gradient in clay content of 16–37% and organic carbon concentrations of 10–15 g kg〈sup〉−1〈/sup〉. Our results demonstrate how soil texture governs aggregate size distributions: most water-stable microaggregates were found to be of approximately 30 μm diameter, independent of the clay content gradient. High-clay soils contain more water-stable macroaggregates (〉250 μm) and larger microaggregates in the 50–180 μm size range. The low-clay soils, on the other hand, contained more non-aggregated sand-sized particles 〉100 μm which probably hampered the buildup of larger aggregates. The size distribution of particles 〈100 μm in size fractions 〈250 μm showed a similar prevailing soil texture pattern, with approximately 24% clay, 59% silt, and 17% sand-sized particles at all clay contents. In contrast to the prevailing texture pattern along the clay content gradient, 4% more clay-sized particles helped build up water-stable macroaggregates. In the low-clay soils, the aggregates were smaller and the size fractions 〈53 μm had higher OM concentrations. This indicates that the low-clay soils held most of their OM in smaller microaggregates. Such arrangement of OM in smaller microaggregates demonstrates that soil texture may control OM stabilization mostly indirectly via the distribution of OM in different aggregate fractions. The occlusion of microaggregates in larger structures led to lower alkyl:O/N-alkyl ratios in 〈sup〉13〈/sup〉C nuclear magnetic resonance (NMR) spectroscopy, indicating increased preservation.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 355〈/p〉 〈p〉Author(s): Pengpeng Duan, Yanfeng Song, Shuangshuang Li, Zhengqin Xiong〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Greenhouse vegetable field is one of the main sources of agricultural nitrous oxide (N〈sub〉2〈/sub〉O) emissions via multiple pathways regulated by different microbes. However, the relative contributions of nitrifier nitrification, nitrifier denitrification, nitrification-coupled denitrification and heterotrophic denitrification to N〈sub〉2〈/sub〉O production with temperature change in different greenhouse vegetable soils are poorly understood. In this study, combined approaches of the 〈sup〉15〈/sup〉N–〈sup〉18〈/sup〉O labeling technique and transcriptome analyses were applied to investigate the pathways of N〈sub〉2〈/sub〉O production (nitrifier nitrification, nitrifier denitrification, nitrification-coupled denitrification and heterotrophic denitrification) under 15, 25 and 35 °C in six greenhouse vegetable field soils in mainland China. The results show that heterotrophic denitrification was an important source of N〈sub〉2〈/sub〉O in acidic greenhouse vegetable soils, whereas nitrifier nitrification was the dominant source of N〈sub〉2〈/sub〉O in alkaline greenhouse vegetable soils. In addition, the contribution of nitrifier denitrification and nitrification-coupled denitrification to N〈sub〉2〈/sub〉O production in alkaline greenhouse vegetable soils were higher than in acidic greenhouse vegetable soils. The contribution of nitrification-coupled denitrification increased with temperature at 15–35 °C, whereas nitrifier denitrification increased with temperature at 15–25 °C. Overall, high temperature decreased the contribution of nitrifier nitrification to N〈sub〉2〈/sub〉O production. These results have important implications for understanding the temperature-dependent N〈sub〉2〈/sub〉O production pathways and for mitigating agricultural N〈sub〉2〈/sub〉O emissions under different soil and temperature conditions.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0016706119305762-ga1.jpg" width="500" alt="Unlabelled Image" title="Unlabelled Image"〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 354〈/p〉 〈p〉Author(s): Fabian E. Gruber, Jasmin Baruck, Volkmar Mair, Clemens Geitner〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Parent material is an important factor of soil formation and consequently plays a dominant role in both traditional field soil survey and digital soil mapping. The emergence of a new generation of detailed geological maps at high spatial resolution in South Tyrol raises the question of how to effectively incorporate these into soil mapping efforts. By comparing the units of these geological maps with the parent material description of soil pits, we evaluate to what extent these can be used as soil parent material maps. Random forest classification and feature selection are applied to highlight those terrain parameters that i) best distinguish between the different surficial geology units, ii) separate soil profile sites with different soil parent material, and iii) can be used together with the geologic map to train a classifier to model the distribution of soil parent material in the study area. The main issue detected by analyzing the differences between the geologic map units and the soil parent material information is the dominant role of till, which acts as soil parent material for a large number of soils located on different geological map units. While slope debris is another class on which geological map and soil pit descriptions often disagree, the issues concerning its misclassification are connected more to categorical transitions between soil parent material classes. Terrain parameters characterizing surface roughness, specifically a combination of vector ruggedness measure (VRM) and topographic roughness index (TRI), were identified as being best suited to join the geological map units in modeling soil parent material and indicate areas where till as soil parent material should be expected. By evaluating these results together with the distribution of soil types, a geologic-topographic characterization is performed for each geological map unit, with the aim of highlighting specific combinations of geological units and topographical situations which should be in the center of future detailed soil surveys, consequently facilitating the soil mapping procedure.〈/p〉〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 354〈/p〉 〈p〉Author(s): I. Kouchami-Sardoo, H. Shirani, I. Esfandiarpour-Boroujeni, J. Álvaro-Fuentes, H. Shekofteh〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Threshold friction velocity (u〈sub〉⁎t〈/sub〉) is a very important parameter, which represents wind erosion potential. Because of the difficulty of measuring u〈sub〉⁎t〈/sub〉, it would be advantageous if u〈sub〉⁎t〈/sub〉 could be estimated indirectly from its effecting factors that can be easily measured. The main purpose of this research was to quantify relationships between u〈sub〉⁎t〈/sub〉 and various topsoil features using inexpensive approaches. To prepare a reliable dataset, we used a portable wind tunnel for measuring u〈sub〉⁎t〈/sub〉 at a total of 118 observation points in Kerman province, southeast Iran. We developed a non-dominated sorting genetic algorithm II (NSGA-II), specifically designed to operate with artificial neural network (ANN) to select the most determinant properties that influence u〈sub〉⁎t〈/sub〉. A permutation of nine input features including surface crust (SC), gravel coverage (GC), very fine sand (VFS), fine sand (FS), very coarse sand (VCS), electrical conductivity (EC), sodium adsorption ratio (SAR), calcium carbonate equivalent (CCE), and mean weight diameter (MWD), was introduced as explanatory variables. We also examined the potential power of using a Multi-Layer Perception (MLP) neural network for prediction of u〈sub〉⁎t〈/sub〉 changes in response to spatial variation of the selected features. The results of constructed MLP model revealed the ability of the model for u〈sub〉⁎t〈/sub〉 prediction and showed that the coefficient of determination (R〈sup〉2〈/sup〉) values were 0.91 and 0.89 for training and testing data, respectively. Furthermore, acceptable level of the statistical validation criteria verified reliable performance of the MLP model. This research provided a powerful basis for prediction of u〈sub〉⁎t〈/sub〉 from topsoil features and surface roughness in arid and semi-arid areas of Iran; however, its generic framework could be used to other arid and semi-arid regions with similar challenges.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 354〈/p〉 〈p〉Author(s): José A.M. Demattê, André Carnieletto Dotto, Ariane F.S. Paiva, Marcus V. Sato, Ricardo S.D. Dalmolin, Maria do Socorro B. de Araújo, Elisângela B. da Silva, Marcos R. Nanni, Alexandre ten Caten, Norberto C. Noronha, Marilusa P.C. Lacerda, José Coelho de Araújo Filho, Rodnei Rizzo, Henrique Bellinaso, Márcio R. Francelino, Carlos E.G.R. Schaefer, Luiz E. Vicente, Uemeson J. dos Santos, Everardo V. de Sá Barretto Sampaio, Rômulo S.C. Menezes〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The present study was developed in a joint partnership with the Brazilian pedometrics community to standardize and evaluate spectra within the 350–2500 nm range of Brazilian soils. The Brazilian Soil Spectral Library (BSSL) began in 1995, creating a protocol to gather soil samples from different locations in Brazil. The BSSL reached 39,284 soil samples from 65 contributors representing 41 institutions from all 26 states. Through the BSSL spectra database, it was possible to estimate important soil attributes, such as clay, sand, soil organic carbon, cation exchange capacity, pH and base saturation, resulting in differences among the multi-scale models taking Brazil (overall), regional and state scale. In general, spectral descriptive and quantitative behavior indicated important relationship with physical, chemical and mineralogical properties. Statistical analyses showed that six basic patterns of spectral signatures represent the Brazilian soils types and that environmental conditions explain the differences in spectra. This study demonstrates that spectroscopy analyses along with the establishment of soil spectral libraries are a powerful technique for providing information on a national and regional levels. We also developed an interactive online platform showing soil sample locations and their contributors. As soil spectroscopy is considered a fast, simple, accurate and nondestructive analytical procedure, its application may be integrated with wet analysis as an alternative to support the sustainable management of soils.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0016706118318548-ga1.jpg" width="301" alt="Unlabelled Image" title="Unlabelled Image"〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 354〈/p〉 〈p〉Author(s): Fujun Niu, Zeyong Gao, Zhanju Lin, Jing Luo, Xingwen Fan〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Soil hydrological processes are extremely complex in high-altitude regions and are recognized to have positive effects on soil quality, nutrient cycling, herbage yield, and runoff generation. However, soil hydrological processes have not been fully quantified in permafrost regions of the Qinghai-Tibet Plateau (QTP). To fill this gap, the soil water dynamics, soil water storage, soil infiltration processes, soil water retention and soil hydraulic conductivity were systematically monitored in different alpine ecosystems (alpine wet meadow (AWM), alpine meadow (AM), and alpine steppe (AS)). The results revealed that the soil water content was significantly higher in AWM soil in the shallow layer, while it was higher in AM soil in the deeper layer. Moreover, the response of soil water to rainfall was markedly more sensitive in AS soil than in AM and AWM soils. The average soil water storage amount reached 440 mm in the 0–100 cm soil interval of the AM, which was nearly 1.6-fold higher than that in the AS and 1.2-fold higher than that in the AWM. The existence of vegetation enhanced the soil infiltration rates in AWM and AM soils 1.3-fold and 1.5-fold, respectively, and decreased the soil infiltration rate 1.2-fold in AS soil. Nuclear magnetic resonance (NMR) results indicated that soil water in AS soil was mainly composed of capillary water and mobile water but was composed of bound water and capillary water in AWM soil and AM soil, respectively. The results from a redundancy analysis (RDA) demonstrated that the vegetation in the study region regulates the soil hydrological regime by altering the soil structure and soil biochemistry. Moreover, the mechanism of vegetation influence on soil hydrological processes suggests that the regional runoff generation will shift with the vegetation succession. The information obtained in this study may aid in the understanding of changes in the ecological environment and regional hydrological cycles under climate change.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 354〈/p〉 〈p〉Author(s): M. Díaz-López, C. García, I. Garrido, S. Navarro, N. Vela, E. Nicolás, J. Fenoll, F. Bastida〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Pesticides are chemical compounds, mostly synthetic, which are used widely in agricultural fields to prevent and to control pests and soil-borne diseases. The synthetic nature of these compounds makes some of them non-biodegradable and they may accumulate in harmful concentrations in soils. Solarization seems to be a non-chemical strategy that could enhance pesticide degradation in soils. Here, we evaluate the combined impact of pesticides and solarization on the microbial community of a Mediterranean soil. For this purpose, enzyme activities, basal respiration, and the biomass and composition of the microbial community (through analysis of phospholipid fatty acids, PLFAs) were evaluated in solarized and non-solarized soils, in a 90-day greenhouse experiment with a combination of different pesticides. The degradation of the pesticides in the solarized soils was 30% greater than in non-solarized samples. However, solarization also affected the soil microbial community. The soil respiration was lowest in solarized samples without pesticides, while the enzyme activities were greater in non-solarized samples (with and without pesticides). Both the bacterial and fungal PLFA contents declined in solarized samples. The G+/G− ratio was highest in the solarized samples without pesticides and in the non-solarized samples with pesticides. Considering such impacts on the soil microbial community and the relationship of soil microbes with soil ecosystem services, the utilization of solarization must be carefully considered when adopting strategies for pesticide degradation in Mediterranean soils.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 354〈/p〉 〈p〉Author(s): Imane Haidara, Meryem Tahri, Mohamed Maanan, Mustapha Hakdaoui〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Erosion of soil and land degradation is a worldwide phenomenon caused by natural occurrence and which is accelerated by climate change. This study evaluated soil erosion vulnerability using the Fuzzy Analytical Hierarchy Process (FAHP) multi-criteria method and Geographical Information System (GIS). Six criteria were used to create the soil erosion cartography: rainfall, land cover, soil classification, slope gradient, drainage density, and land use. This method calculated the corresponding criteria weights on the feedback of several studies, and research, which may be used to determine the effectiveness in controlling soil erosion around the world. Our results highlighted the variability of erosion and clearly identified the areas at risk. Five degrees of erosion were noted: very slight erosion and slight erosion located in the south of the study site, moderate erosion present throughout the catchment area, high as well as very high erosion situated in the north of the catchment area.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 355〈/p〉 〈p〉Author(s): Xuebin Xu, Changwen Du, Fei Ma, Yazhen Shen, Ke Wu, Dong Liang, Jianmin Zhou〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Spectroscopy is a useful method for soil monitoring because of its environmental friendliness, and its ability to produce rapid, nondestructive, simultaneous multi-element analysis. In this work, data fusion strategies for laser-induced breakdown spectroscopy (LIBS) and attenuated total reflectance Fourier-transform mid-infrared spectroscopy (FTIR-ATR), as well as a combination of multivariate calibration methods were investigated for prediction of soil organic matter (SOM) content. The root mean square error (RMSE) and residual prediction deviation (RPD) of the calibration and validation sets, systematic error, and residual assessment, were applied to evaluate the robustness and accuracy of these predictions. The results of a principal component analysis (PCA) indicated that baseline wander present in the spectral data could be effectively removed using morphological weighted penalized least squares (MPLS) and wavelet transform (WT) algorithms. The quantitative prediction ability of SOM content by a partial least squares regression (PLSR) model could be improved using principal component weighted mean (PCWM) and Euclidean distance weighted mean (EDWM) algorithms applied to parallel LIBS spectra. The prediction ability of SOM content was dramatically improved using mid-level data fusion based on the concatenation of latent variables of LIBS and FTIR-ATR spectra obtained by partial least squares algorithm. The considerable prediction accuracy and robustness were achieved using the PLSR model (R〈sub〉V〈/sub〉〈sup〉2〈/sup〉 = 0.792, RMSE〈sub〉V〈/sub〉 = 1.76 g kg〈sup〉−〈/sup〉〈sup〉1〈/sup〉, and RPD〈sub〉V〈/sub〉 = 2.16), the support vector regression (SVR) model (R〈sub〉V〈/sub〉〈sup〉2〈/sup〉 = 0.811, RMSE〈sub〉V〈/sub〉 = 1.68 g kg〈sup〉−〈/sup〉〈sup〉1〈/sup〉, and RPD〈sub〉V〈/sub〉 = 2.27), and the artificial neural network (ANN) model (R〈sub〉V〈/sub〉〈sup〉2〈/sup〉 = 0.830, RMSE〈sub〉V〈/sub〉 = 1.60 g kg〈sup〉−〈/sup〉〈sup〉1〈/sup〉, and RPD〈sub〉V〈/sub〉 = 2.39). The findings from this work suggest that the use of LIBS and FTIR-ATR spectra in combination with multivariate calibration can be a simple, fast, and nondestructive approach to monitor SOM. This strategy is potentially of great significance in the evaluation of soil fertility, the management of soil nutrients, and in guiding the agricultural production of precision agriculture.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 355〈/p〉 〈p〉Author(s): Moritz Laub, Sergey Blagodatsky, Yvonne Funkuin Nkwain, Georg Cadisch〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Peak area (PA) integration of diffuse reflectance mid infrared Fourier transform spectroscopy (DRIFTS) spectra is useful to study soil organic matter (SOM) quality and as a potential modelling proxy. Residual water of soil samples after drying affects DRIFTS spectra, mainly in the region 〉2500 cm〈sup〉−〈/sup〉〈sup〉1〈/sup〉. Therefore, SOM quality related PA at different wavenumbers should be influenced to varying degrees. We studied how absolute, normalized and relative PA related to SOM functional groups (at 2930, 1620, 1530 and 1159 cm〈sup〉−〈/sup〉〈sup〉1〈/sup〉), as well as their ratios were influenced by oven drying of soil samples at increasing temperatures (from 32 °C to 105 °C). All organic and even mineral associated PA significantly increased with drying temperature. The PA of aliphatic C〈img src="https://sdfestaticassets-eu-west-1.sciencedirectassets.com/shared-assets/16/entities/sbnd"〉H stretching (2930 cm〈sup〉−〈/sup〉〈sup〉1〈/sup〉), located on the shoulder of the broad O〈img src="https://sdfestaticassets-eu-west-1.sciencedirectassets.com/shared-assets/16/entities/sbnd"〉H stretching PA, was influenced most strongly. Our results indicate that using 105 °C as drying temperature and storing samples in a desiccator is the best way to minimize water interference. These findings apply to relative PA and ratios of organic compounds, while no effect of drying temperatures on PA correlations to C or N were found.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 354〈/p〉 〈p〉Author(s): Junhui Chen, Qifeng Wu, Songhao Li, Jiangfei Ge, Chenfei Liang, Hua Qin, Qiufang Xu, Jeffry J. Fuhrmann〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Intensive forest management practices, such as fertilization, understory removal and deep tilling, play an important role in improving plant growth in forests through altering nutrient availability and soil structure. However, how such management affects soil microbial community diversity and functions related to nutrient cycling remains largely unknown. In this study, we investigated the responses of soil bacterial community composition and enzyme activities involved in C, N and P cycling to long-term intensive management, and identified the critical determinants that regulated them across a chronosequence of Moso bamboo forests (0, 10, 15, 20 and 25 years of intensive management) in subtropical China. Our results demonstrated that intensive management decreased soil pH and aggregation and increased mineral nutrient contents. Illumina MiSeq sequencing showed that significant (〈em〉P〈/em〉 〈 0.05) shifts of the soil bacterial community composition occurred after 15 years of management. Diversity indices (phylogenetic diversity, OTU richness and Chao1) generally decreased after 15 years of management. Soil pH, NO〈sub〉3〈/sub〉〈sup〉−〈/sup〉-N, and available P and K contents were key factors shaping the bacterial community composition. Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) predicted lower functional diversity of soil bacterial microbiomes as related to the cycling of amino acids and carbohydrates after 15 and 20 years. The activities of β-glucosidase and phosphatase decreased markedly after 15 years of intensive management, but rebounded after 25 years. Structural equation modeling provided evidence that the response of soil enzyme activities to forest management was mediated by changes in bacterial composition and diversity. Our study suggests that intensive forest management decreases microbial diversity indices and changed community composition, which could have direct consequences for soil functioning.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 July 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 346〈/p〉 〈p〉Author(s): Laura Poggio, Antoine Lassauce, Alessandro Gimona〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉Mapping the extent and locations of peatland at landscape scale has implications for carbon inventories, conservation and ecosystem services assessments. The main aim of this paper was to model and map the extent of northern peat soils while taking into account its uncertainty, and in particular exploring:〈/p〉 〈dl〉 〈dt〉1.〈/dt〉 〈dd〉〈p〉the use of radar Sentinel 1 as alternative to optical sensors to reduce problems due to clouds while taking advantage of the seasonality changes and〈/p〉〈/dd〉 〈dt〉2.〈/dt〉 〈dd〉〈p〉the use of deep learning for peat classification and as application of Digital Soil Mapping.〈/p〉〈/dd〉 〈/dl〉 〈p〉The data sets defining presence or absence of peat in the soil were obtained from different sources and different sampling schemes, densities and distributions. Scotland was used as test case, because of its cloudy weather and fragmented distribution of different types of peat.〈/p〉 〈p〉An extension of the scorpan-kriging approach was used. The trend was estimated with different approaches: Generalized Additive Models, RandomForest and deep learning (convolutional neural networks). Each approach produced the probability of belonging to a class and the predicted class for each pixel. The results were assessed using out-of-sample measures.〈/p〉 〈p〉In this study 108 combinations of data sets and models (including trend approaches, sets of covariates and modelling of the spatial structure) were assessed. Overall, spatially explicit models performed better. The choice of the statistical method can have a significant impact on the predictive performances, while the sets of environmental covariates had a lower impact. Sentinel-1 with morphological features proved to be a good alternative to optical data for peat mapping. It is important to have balanced data sets representing the distribution of the data, because merging heterogeneous sources of data from different populations does not necessarily improve predictions. The use of deep learning and convolutional neural network provided initial promising results.〈/p〉 〈p〉There were large differences in the modelling approaches. These differences and uncertainties need to be taken into account for further modelling such as earth surface modelling or carbon accounting.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 July 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 346〈/p〉 〈p〉Author(s): Haiying Lu, Yanfang Feng, Yuanyuan Feng, Yue Dong, Haijun Sun, Jincheng Xing, Hongbo Shao, Lihong Xue, Linzhang Yang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉Phosphorus (P) is a vital element for plant growth, especially in mudflat-reclaimed soil due to its extra alleviation of adverse effect by salt stress. P availability in mudflat-reclaimed soil is a critical factor for crop yield. In this study, cerium-modified straw biochar (Ce-MSB) derived from maize straw was prepared and characterized and its influence on P availability of the paddy soil was evaluated. The results indicated that the cerium elements were chemically bound to the functional groups of the biochar surface through SEM, EDX and FTIR techniques. The equilibrium process of P by Ce-MSB was described well by the Langmuir isotherm model (〈em〉R〈/em〉〈sup〉2〈/sup〉 〉 0.99). The maximal P adsorption capacity of Ce-MSB was influenced remarkably by temperature. Accordingly, the addition of Ce-MSB significantly decreased the P content of surface water in paddy system after 3 months, while increasing the soil P availability. Furthermore, the incorporation of both common biochar and Ce-MSB into the soil increased the SOM content, while decreased soil pH and EC. Biolog EcoPlateTM trials indicated that Ce-MSB has no significantly negative effects on soil microbial diversity. This study provides valuable information for the source-reduction of P discharge from paddy system and improvement of P availability.〈/p〉 〈p〉Phosphorus (P) is a vital element for plant growth, especially in coastal reclaimed mudflat due to its extra alleviation of adverse effect by salt stress. P availability in mudflat-reclaimed soil is a critical factor for crop yield. In this study, cerium-modified straw biochar (Ce-MSB) derived from maize straw was prepared and characterized and its influence on P availability of the paddy soil was evaluated. The results indicated that the cerium elements were chemically bound to the functional groups of the biochar surface through scanning electron microscopy (SEM), energy dispersive X-ray spectrum scanning (EDX), and fourier transform infrared spectroscopy (FTIR) techniques. The equilibrium process of P (PO〈sub〉4〈/sub〉〈sup〉3−〈/sup〉) by Ce-MSB was described well by the Langmuir isotherm model (〈em〉R〈/em〉〈sup〉2〈/sup〉 〉 0.99). The maximal P adsorption capacity of Ce-MSB was influenced remarkably by temperature, which was 58, 69, and 78 mg g〈sup〉−1〈/sup〉 under 5, 25, and 40 °C, respectively. Under laboratory simulation, the addition of Ce-MSB significantly decreased the P content of surface water in paddy system after 3 months, while increasing the P availability of soil. Furthermore, the incorporation of both common biochar and Ce-MSB into the soil increased the SOM content, while decreased soil pH and EC. Biolog EcoPlateTM trials indicated that Ce-MSB has no significantly negative effects on soil microbial diversity. This study provides valuable information for the source-reduction of P discharge from paddy system and improvement of P availability.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 July 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 346〈/p〉 〈p〉Author(s): Anna-Helena Purre, Raimo Pajula, Mati Ilomets〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Peat excavation has altered carbon balance in large areas in the Northern Hemisphere and turned peatlands from CO〈sub〉2〈/sub〉 sinks to CO〈sub〉2〈/sub〉 sources. Peatland restoration aims at mitigating that situation by supporting CO〈sub〉2〈/sub〉 uptake in these areas through raising the water table, in this way creating conditions for vegetation development and organic matter accumulation. We analysed the relationships between recovering vegetation and CO〈sub〉2〈/sub〉 fluxes on three abandoned peat excavation sites in northern Estonia, which were rewetted and restored using the moss-layer-transfer technique three to ten years before the first measurements. Using chamber measurements, we determined whether these sites were CO〈sub〉2〈/sub〉 sinks or sources during two growing seasons in 2015 (drier) and 2016 (wetter). In the drier growing season, all sites were CO〈sub〉2〈/sub〉 sources from the peatland to the atmosphere (emissions from 1 to 77 g CO〈sub〉2〈/sub〉 m〈sup〉−2〈/sup〉), while in the wetter growing season, two sites were CO〈sub〉2〈/sub〉 sinks (uptake from 13 to 210 g CO〈sub〉2〈/sub〉 m〈sup〉−2〈/sup〉). CO〈sub〉2〈/sub〉 uptake was higher with higher plant and 〈em〉Eriophorum vaginatum〈/em〉 cover, and biomass and cover of 〈em〉Sphagnum〈/em〉. The remotely sensed Normalized Difference Vegetation Index (NDVI) explained about 25% of variation in Net Ecosystem Exchange; CO〈sub〉2〈/sub〉 uptake was higher in plots with higher NDVI values. This provides a potential avenue of investigation of developing remote sensing methods in assessing spatial pattern of CO〈sub〉2〈/sub〉 fluxes in restored peatlands. In order to increase CO〈sub〉2〈/sub〉 uptake in abandoned milled peatlands, it is essential to raise the water level and thus reduce peat oxidation and create conditions for the development of vegetation similar to pristine peatlands.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0016706118320792-ga1.jpg" width="500" alt="Unlabelled Image" title="Unlabelled Image"〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 July 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 346〈/p〉 〈p〉Author(s): Jin-Feng Liang, Jing An, Jun-Qin Gao, Xiao-Ya Zhang, Ming-Hua Song, Fei-Hai Yu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Both biochar and arbuscular mycorrhizal fungi (AMF) can affect plant growth, but little is known about how the interaction between biochar and AMF affects greenhouse gas emissions from plant-soil systems. We tested the hypotheses that biochar and AMF can interact to affect greenhouse gas emissions due to promoted plant biomass and changed soil N availability. We assembled microcosms, each initially grown with three ramets (vegetative individuals) of a clonal, wetland plant 〈em〉Phragmites australis〈/em〉, with or without AMF in soil and with or without biochar addition to soil. Biochar addition alone and AMF presence alone both significantly enhanced biomass of 〈em〉P〈/em〉. 〈em〉australis〈/em〉, but such effects became weaker when they were present simultaneously. The presence of AMF significantly decreased concentrations of chlorophyll and nitrogen (N) in 〈em〉P〈/em〉. 〈em〉australis〈/em〉 and concentrations of NH〈sub〉4〈/sub〉〈sup〉+〈/sup〉-N, NO〈sub〉3〈/sub〉〈sup〉−〈/sup〉-N, inorganic N and total N in soil, but such effects became weaker when biochar was added to soil than when it was not. Biochar addition significantly increased concentrations of chlorophyll and N in 〈em〉P〈/em〉. 〈em〉australis〈/em〉 when AMF were present, but had little impact when AMF were absent. The presence of AMF increased CO〈sub〉2〈/sub〉 emission and CO〈sub〉2〈/sub〉 equivalent independent of biochar addition. The presence of AMF also increased N〈sub〉2〈/sub〉O emission when biochar was added, but decreased it when biochar was not added. We conclude that biochar addition and AMF presence can interact to affect plant growth and N uptake, soil N availability and greenhouse gas emissions from plant-soil ecosystems.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 July 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 346〈/p〉 〈p〉Author(s): Julia Pöhlitz, Jan Rücknagel, Steffen Schlüter, Hans-Jörg Vogel, Olaf Christen〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉Some soil physical properties can easily be measured using classical laboratory methods. However, explicit valuable information on the real morphology of the pore structure as well as soil physical properties cannot be obtained at the same time with classical methods. This requires non-destructive measurements such as X-ray computed tomography (CT).〈/p〉 〈p〉However, explicit valuable information on the real morphology of the pore structure as well as soil physical properties cannot be obtained at the same time with classical methods.〈/p〉 〈p〉This paper combines parameters obtained from CT analysis (mean macropore diameter, macroporosity, pore connectivity, anisotropy) and classical laboratory methods (dry bulk and aggregate density, saturated hydraulic conductivity, mechanical precompression stress) to analyse soil compaction, exemplified on samples from two tillage treatments (cultivator and plough) and at two moisture states (6 and 1000 kPa matric potential) on a Chernozem collected at a soil depth of 16–22 cm (texture 0–30 cm: silty clay loam).〈/p〉 〈p〉The study shows that the matric potential can have a decisive impact on the mechanical stability of soil. In the loose but less stable plough treatment a more negative matric potential was clearly beneficial to the mechanical stability. In already dense soil structures, as in the cultivator treatment, a reduction of water content was less effective in increasing soil stability.〈/p〉 〈p〉The CT parameters were all closely and uniquely related to each other. The shown CT parameters can be used for a standardized characterization of the soil. Ploughing has a positive effect on soil structure which persists only as long as macroporosity and mean macropore diameter remain high. Plough maintains higher pore connectivity when compacted under dry conditions.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 347〈/p〉 〈p〉Author(s): Davi do Vale Lopes, Carlos Ernesto G.R. Schaefer, José João Lelis Leal de Souza, Fábio Soares de Oliveira, Felipe Nogueira Bello Simas, Mayara Daher, Davi Feital Gjorup〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Although acid sulfate soils have been previously reported in Maritime Antarctica, no detailed study about the nature of the sulfide oxidation process and its effect on pedogenesis has been carried out to this day. The present study evaluate the soil genesis from Barton Peninsula along two toposequences developed under sulfides influence, emphasizing active chemical processes in a typical periglacial environment of Maritime Antarctica, and the unusual formation of petroplintite. Seven pedons were selected, described, sampled and classified according to the U.S. Soil Taxonomy and the IUSS Working Group WRB. Soil morphological, physical, chemical, microchemical and mineralogical properties were analyzed. The geochemical composition (total contents of Al, Ca, Co, Cu, Fe, K, Mg, Na, Ni, S, Si, Ti, Th, V and Zn) was determined with X-ray Fluorescence Spectrophotometer. Unlike previous studies that considered chemical weathering as insignificant in Barton Peninsula, this study demonstrates that some areas have active and pronounced chemical weathering processes (sulfurization and phosphatization), which cannot be underestimated. These chemical processes, together or individually, promote strong soil acidification, release exchangeable bases and accelerate mineralogical changes. Precipitation of secondary crystalline iron oxides, plinthization and petroplintite formation occur in these soils, resulting in unusual pedogenic features, unknown to occur in Antarctica to this day. Further studies on Antarctic soils with petroplinthic horizons, with or without ornithogenesis, deserve attention regarding micromorphological attributes and clarification about these new, unusual pedological processes in periglacial environments and their possible use as indicators of environmental change.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 347〈/p〉 〈p〉Author(s): Wenguang Sun, H. Magdi Selim〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Quantitative understanding of kinetics and mechanisms heavy metal adsorption-desorption and transport processes, batch and stirred-flow experiments were carried out with vanadium (V) and molybdenum (Mo) on soils at different reaction conditions and time scale. Batch experiments indicated that adsorption of V and Mo on soils was highly nonlinear and time-dependent, where V and Mo retention showed typical biphasic reaction kinetics. The stirred-flow experiments showed that both V and Mo adsorption consisted of a fast initial reaction, as indicated by the fact that effluent solute concentration was close to zero for the first few minutes. A stirred-flow multi-reaction model (MRM) which accounts for slow as well as fast reactions of the reversible and irreversible type was developed to describe V and Mo adsorption and desorption processes on soils. Based on model simulations and experimental tracer breakthrough curves (BTCs) results, we concluded that the proposed model is valid for stirred-flow conditions. The strong retardation and slow release behaviors of V and Mo from stirred-flow experiments were successfully described using the proposed stirred-flow MRM where retardation and irreversible reactions were necessary. Our work provides a general stirred-flow model which is capable of describing reactive and non-reactive solutes.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 July 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 346〈/p〉 〈p〉Author(s): Bin Zhang, Ryan Beck, Qingmin Pan, Mengli Zhao, Xiying Hao〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Soil physical and chemical properties are critical indicators for soil health assessment. It is important to understand how these qualities respond to different grazing intensities at different landscape slope positions. This study evaluated how soil physical and chemical properties respond to cattle grazing intensity and slope position on a rough fescue grassland. Cattle have been grazing at four stocking rates, 0, 1.2, 2.4 and 4.8 animal-unit-months (AUM) ha〈sup〉−1〈/sup〉 since 1949 to simulate Control (CK), Light (L), Heavy (H), and Very Heavy (VH) grazing intensities. Surface soil penetration resistance was measured using a portable penetrometer and soil samples were taken from the top and bottom slope positions for each grazing paddock (but only from the top position for CK) in September 2016. Soil texture, aggregate stability, pH, available phosphorus (AP), water-soluble ions concentration and soil cation exchange capacity (CEC) were determined. Bulk density, porosity and hydraulic properties were measured using a HYPROP system. The S-index, the slope at the inflection point on the soil moisture retention curve, was calculated. Soil clay and silt contents were lower in VH than L treatments; total porosity, air capacity, and saturated water content followed the same pattern. However, the opposite was true for sand content, penetration resistance, and bulk density, with differences between the two grazing treatments greater at the top than the bottom slope position. Grazing changed the shape of soil moisture retention curve in both slope positions with the curve steeper in L than H and VH treatments. The S-index and saturated hydraulic conductivity were reduced by grazing but their responses to slope position and its interaction with grazing intensity were not significant. Soil pH, AP, and water-soluble Na〈sup〉+〈/sup〉, K〈sup〉+〈/sup〉, Mg〈sup〉2+〈/sup〉, Ca〈sup〉2+〈/sup〉 and SO〈sub〉4〈/sub〉〈sup〉2−〈/sup〉 concentration increased with the animal stocking rate while Cl〈sup〉−〈/sup〉 and CEC were not affected. Similarly, greater increases in soil pH with increased animal stocking rates were observed in the top than bottom position, while AP, Na〈sup〉+〈/sup〉, K〈sup〉+〈/sup〉, and SO〈sub〉4〈/sub〉〈sup〉2−〈/sup〉 increased with animal stocking rate only in the bottom position. Our results indicate that soil physical properties may be more sensitive to grazing at the top than bottom of a slope. Thus, slope should be considered when developing rangeland soil health assessment indices and grazing management strategies.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 347〈/p〉 〈p〉Author(s): Jan Dietel, Kristian Ufer, Stephan Kaufhold, Reiner Dohrmann〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The acidic weathering process of soils is a worldwide problem. In this process, Al〈sup〉3+〈/sup〉 is dissolved from silicates and intercalated into swellable clay minerals by replacing exchangeable cations such as Na〈sup〉+〈/sup〉 or Ca〈sup〉2+〈/sup〉. Al〈sup〉3+〈/sup〉 polymerizes in the interlayer regions of the clay minerals to form fixed oligomers, which significantly reduces the clay minerals swellability and cation exchange, and hence, the soil fertility. The layer silicates with fixed (Al) oligomers in the interlayer are known as hydroxy-interlayered minerals, such as hydroxy-interlayered smectite (HIS), or hydroxy-interlayered vermiculite (HIV). These phases have been recognized for many years, but it is still problematic to adequately characterize the details of their structure and to determine their proportion in soils, based on X-ray diffraction (XRD), which is the most common method for mineral quantification. In the present study, two crystal structure models are used to allow characterization and quantitative determination of HIS in artificial and natural soils, using the Rietveld refinement technique based on XRD. Both models are identical regarding the 2:1 layer and the description of the hydroxy-interlayering, but differ in the effect imposed by environmental conditions. The first model describes the smectite in the ethylene glycol saturated state (≈17 Å), commonly used by clay scientists as a diagnostic intercalate for swellable smectitic or vermiculitic layers in pure smectite or vermiculite or interstratifications. The second model describes the smectite in the air-dried (AD) state including the collapsed state (≈10 Å), one-water layer state (≈12.5 Å), and two-water layer state (≈15 Å). Both models are used to fit XRD patterns obtained from samples with preferred orientation and from XRD random powder specimens, each including structural disorder effects. The models provide plausible refinement results with respect to crystallographic parameters and quantitative proportions. The degree of hydroxy-interlayering gives an estimate of how many exchangeable cations of the smectite were replaced by fixed Al oligomers that inhibit expandability. This value corresponds to calculated values within a range of precision of ≤15% mol/mol. Physical mixtures of HIS with clinochlore, muscovite, quartz, and albite were quantified using the proposed crystal structure model. Results showed that the HIS model delivers reliable quantification results (deviations from actual values ≤3% w/w) which may be applied also for natural soil.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 July 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 346〈/p〉 〈p〉Author(s): Xueyu Zhao, Jie Wang, Dongxue Zhao, Nan Li, Ehsan Zare, John Triantafilis〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In the cotton growing areas of NSW issues associated with water use efficiency and storage reservoirs are problematic, because leakage has led to point source salinization in some areas. Information about the areal distribution of clay is therefore necessary to assist farmers to understand where existing water storages may be better relocated. To map clay efficiently, we show how electromagnetic (EM) induction data from a reconnaissance survey of EM38 and EM34 instruments can be used in association with an EM inversion software package called EM4Soil. This is because the collected apparent electrical conductivity (EC〈sub〉a〈/sub〉 – mS m〈sup〉−1〈/sup〉) data can be inverted to estimate the true electrical conductivity (σ – mS m〈sup〉−1〈/sup〉) and correlated with clay. The first aim was to develop a quasi-two-dimensional (Q-2D) model, which could be used to establish a linear regression (LR) relationship between σ and clay collected from 10 soil sample locations to a depth of 12 m, along a single transect of EM38 and EM34 EC〈sub〉a〈/sub〉 data. This was achieved with an LR equation of the form Clay = 22.12 + 0.20σ with a good correlation coefficient (R〈sup〉2〈/sup〉 = 0.74). The second aim was to use the LR to predict clay using a quasi-3D three-dimensional (Q-3D) model developed from EM38 and EM34 electrical conductivity (EC〈sub〉a〈/sub〉) data collected on an approximate 0.5–1 km grid across 50,000 ha. A validation set of clay, collected from 34 soil sample locations, indicated a good concordance was achieved (Lin's = 0.80). We conclude the approach provides useful information on a reconnaissance scale and indicates where more detailed information may be collected to confirm problematic areas. In this regard, suitable structural work for improvements can be suggested. In addition, locations can be identified and where more suitable locations for storages can be investigated. To better resolve the areal short scale variation and where the present and prior streams are juxtaposed against the clay alluvial plain, more EC〈sub〉a〈/sub〉 data should be collected on a finer grid. To improve resolving the depth of clay and the underlying migrational channels, EC〈sub〉a〈/sub〉 data from an EM31 or a DUALEM-421 instrument could also be collected and used in inversion modelling.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 July 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 346〈/p〉 〈p〉Author(s): Mao Tang, Daniel C. Keck, Weixin Cheng, Hui Zeng, Biao Zhu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Rhizosphere respiration (from roots and rhizosphere microbes utilizing root-derived carbon (C)) is a significant component of soil respiration, and rhizosphere priming effect (RPE, change in soil C decomposition by the presence of living roots in the rhizosphere) is crucial for regulating soil C decomposition. However, the relationships between rhizosphere respiration and RPE and root traits (such as biomass and nitrogen (N) concentration) across plant species and growing conditions are not fully resolved. In this study, we investigated rhizosphere respiration rate and RPE of three grassland species (a grass, a forb and a legume) using a continuous isotope-labeling technique. We found a significantly positive relationship between root-mass-specific rhizosphere respiration rate and root N concentration across the three species and two types of mesocosms (small pots and large buckets), and the scaling exponents were approximately one (indicating isometric scaling). Further, soil organic matter (SOM) decomposition rate was not statistically different between the planted treatments and the unplanted control, suggesting insignificant RPE at the early flowering stage (90 days after seeding) for these three species. Likely, respiration from rhizodeposition (root inputs to soil during the 90-day labeling period) was not included in SOM decomposition by the isotope labeling method, which underestimates SOM decomposition and may partly contribute to the lack of RPE of the three species. Overall, our results show that rhizosphere respiration rate is scalable with root N concentration across different plant species and growing conditions, while RPE of these grassland species at the early flowering stage was insignificant.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 April 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 339〈/p〉 〈p〉Author(s): Peter Lindtner, Erika Gömöryová, Dušan Gömöry, Slavomír Stašiov, Vladimír Kubovčík〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Fossorial rodents through their burrowing activities are important disturbance agents in grassland ecosystems. The European ground squirrel (〈em〉Spermophilus citellus〈/em〉) is a medium-sized ground squirrel occurring in central and south-eastern Europe. The aim of the study was to explore changes of physico-chemical and biological soil properties during mound development created by the European ground squirrel. The study was conducted at three study sites in the Western Carpathians. We sampled newly created mounds consisting of fresh excavated soil without vegetation, and old mounds with developed vegetation. We also collected control samples of undisturbed soil in the distance of 5 m to the north direction from each selected mound. We took soil samples for bulk density measurements, chemical and biological analyses from the depth of 0–0.1 m. The results showed that some soil properties were unchanged by mound formation and also across the mound development (e.g., Ca〈sup〉2+〈/sup〉 concentration, richness and diversity of microbial communities). Several soil properties were altered by mound formation, but with no differences during the mound development (e.g., pH, sulphur concentration). On the other hand, some soil properties showed recovery patterns during the mound development towards an undisturbed soil (e.g., soil bulk density, carbon and nitrogen concentrations). Finally, a few properties showed enhanced values on the old mounds (e.g., phosphorus and potassium concentrations, N-mineralization and heterogeneity of microbial communities). These findings suggest that the European ground squirrel through physical disturbance and resources modulation creates soil patchiness and maintains heterogeneity of European grasslands influencing functions (e.g. soil fertility) and processes (e.g. soil aeration, decomposition and nutrient cycling) in grassland soils.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 358〈/p〉 〈p〉Author(s): Lanlan Du, Rui Wang, Xin Gao, Yaxian Hu, Shengli Guo〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Soil erosion and deposition occur widely from regional to global scales and have profound impacts on ecological services and sustainability. Despite their crucial roles in biogeochemical cycles, the responses of soil bacterial communities to soil erosion and deposition remain largely unclear. In this study, a field simulation experiment was conducted to examine variation in soil bacterial communities across eroding slopes and depositional zones with three slope gradients (5°, 10° and 20°) on the Loess Plateau of China (2015–2017). The results showed that soil physicochemical properties were altered by redistribution of runoff and sediment across eroding slopes and depositional zones. Soil bacterial alpha diversity was higher in the depositional zones of both 10° and 20° slopes compared with the 5° reference slopes but no markedly difference was found between eroding slopes and reference slopes. By contrast, bacterial community structure differed between eroding slopes and reference slopes but not between depositional zones and reference slopes. Differentiation of bacterial communities between eroding slopes and depositional zones increased with increasing slope gradients. The bacterial network was greater and more complex within depositional zone than eroding slope, indicating more extensive bacterial interactions and greater community stability potential. Erosion- and deposition-induced redistribution of soil moisture, soil organic matter, available P, and available K were the key determinants of variation in bacterial community structure. Our findings demonstrate the contrasting effects of soil erosion and deposition on soil bacterial communities, which should be given further attention across eroding landscapes.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 358〈/p〉 〈p〉Author(s): Tamara Djerdj, Domagoj K. Hackenberger, Davorka K. Hackenberger, Branimir K. Hackenberger〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Earthworm behavior represents a valuable endpoint in ecological and ecotoxicological studies, providing insight into individual- and population-level responses of organisms to ecological factors and xenobiotics. Difficulties in observing activities of soil-dwelling organisms come from the soil matrix surrounding the animals. We present an automated system for continuous monitoring of earthworm behavior directly in the soil. Performances of the developed system are tested in an avoidance test set-up. The developed system includes a 2D terrarium serving as an experimental compartment and a deep convolutional neural network model for continuous monitoring of earthworm behavior. Quantification of activity of organisms is based on the predictions of the neural network model made from image sequences captured during the exposure. Performance of the system was validated by comparison with results of the standard avoidance test, using H〈sub〉3〈/sub〉BO〈sub〉3〈/sub〉, a standard pollutant. The presented system represents a simple, cost-effective, fast, accurate and objective tool for continuous earthworm behavior monitoring in ecological and ecotoxicological studies. Source code and training data of this system are made freely available on GitHub.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 359〈/p〉 〈p〉Author(s): Andrea Jilling, Daniel Kane, Alwyn Williams, Anthony C. Yannarell, Adam Davis, Nicholas R. Jordan, Roger T. Koide, David A. Mortensen, Richard G. Smith, Sieglinde S. Snapp, Kurt A. Spokas, A. Stuart Grandy〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉Particulate organic matter (POM) is considered an “active” source of nitrogen (N) in cultivated soils, responding readily to management and being more physically accessible to decomposers than mineral-associated forms of organic matter. However, there is increasing evidence that mineral-associated organic matter (MAOM) can also exhibit short-term changes to management that may impact plant and microbial N dynamics. In this study, we investigated how N within soil organic matter fractions responded to three years of tillage and cover crop treatments. We collected soils from a row-crop (maize-soybean rotation) field experiment replicated across three sites in the north central and mid-Atlantic United States: a high-soil organic matter site (3.1% soil organic carbon) in Illinois (IL) and two sites in Michigan (MI) and Pennsylvania (PA) with lower soil organic matter content (1.0% and 1.4% soil organic carbon, respectively). Management treatments included two levels of tillage (chisel plow and ridge tillage) and two levels of cover crop (with and without rye cover crop). Using an optimized sonication method coupled with particle size separation, we isolated and analyzed for N content free POM, occluded POM, a coarse silt fraction, and MAOM. Using partial least squares regression, we also explored broad cross-site relationships between soil organic matter (SOM) fractions, soil N availability, and crop performance.〈/p〉 〈p〉Both particulate and fine fractions responded to tillage and cover crop treatments, but patterns varied by site and fraction. In the low-SOM MI and PA soils, ridge tillage and cover cropping both increased N within POM fractions. The response to ridge tillage was most pronounced, with a 76% and 24% increase in occluded POM N content in MI and PA, respectively. In contrast, at the IL site (high-SOM), the inclusion of cover crops led to higher N, specifically within the fine fractions (coarse silt and MAOM). Cover cropping increased MAOM N content in IL by 24%. When analyzing all sites together, variables associated with fine fractions were more closely associated with N mineralization and crop performance. MAOM can be responsive to short-term management practices and, along with POM, may also be potential sources of N for crops.〈/p〉 〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S001670611930552X-ga1.jpg" width="245" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 June 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 344〈/p〉 〈p〉Author(s): Michael P. Schmidt, Carmen Enid Martínez〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Dissolved organic matter (DOM) represents a fraction of soil organic matter essential to many biogeochemical processes in surface soils and subsoils. Given its dynamic nature, DOM is known to be sensitive to land management practices. This study investigates the influence of tillage on DOM dynamics, including amount and composition of DOM, through a soil profile up to 72 cm depth from moldboard plowed (MB) and no-till (NT) plots in a Mid-Atlantic agroecosystem. Composition of DOM is probed using UV/Visible spectrophotometry (UV/Vis), Fourier transform infrared spectroscopy (FTIR) and fluorescence excitation-emission matrices (EEMs). Tillage decreases extractable DOM at the topmost depth interval studied (0–12 cm), with similar amounts extracted at depths below this point from MB and NT soils. DOM content of MB and NT soils decreases with depth, following a gradual decline in NT soils and a sharp decrease below the plow layer (20 cm) in MB soils. In both soils, chemical composition of DOM becomes less aromatic and less polysaccharide-like in character with depth accompanied by a relative enrichment in carboxylate groups. EEMs demonstrate that species within DOM follow a corresponding transition from conjugated fluorophores to moieties attributable to simple phenol, protein, amino acid and nucleic acid-like DOM constituents. These depth trends in functional group composition follow a distribution similar to DOM content, with observed transitions more abrupt in the MB than NT soils and marked by the plow layer. The decrease in DOM content with depth and the aforementioned shifts in DOM characteristics point to sorptive fractionation of DOM by the soil matrix and/or a conversion from more plant-derived DOM near the surface to more microbially processed DOM in subsoils. Overall, this work further highlights the impact of tillage on DOM behavior below the zone of physical disruption, suggesting that tillage also influences downstream DOM dynamics.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 June 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 344〈/p〉 〈p〉Author(s): Mary-Anne Lowe, Falko Mathes, Meng Heng Loke, Gavan McGrath, Daniel V. Murphy, Matthias Leopold〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Soil water repellency (SWR) is an agricultural concern as it limits plant available water, leading to decreased crop yields at times when a drying climate and expanding population place increasing pressure on food production. Here we assessed a microbial inoculation that secretes biosurfactants and lipolytic enzymes and a chemical surfactant's ability to mitigate SWR. We applied either 〈em〉Bacillus subtilis〈/em〉 (Gm), surfactant (Gs), 〈em〉Bacillus subtilis〈/em〉 with surfactant (Gms) or no treatment (G) to a gamma-irradiated, naturally water-repellent, agricultural soil, with the same soil as an un-sterilised, untreated control (C). Soil water content and the persistence of SWR in a water-repellent core (4 × 4 × 3 cm) were measured during 19 days of repeated soil wetting and drying. Meso-scale, 3D electrical resistivity tomography (ERT) was developed for the continuous, non-destructive measurement of the patterns and volume of water content in the soil, however, effectiveness was limited as the electrical current (5 mA) restricted microbial activity. Destructive measurements of soil water content and potential SWR were conducted in 1 cm soil layers throughout each core. The persistence of SWR decreased over time in all treatments apart from treatment G. SWR was removed by day 12 within the Gm treatment, and was not exhibited immediately after wetting in treatments Gs and Gms. The Gs treatment also increased water content immediately while treatment Gm increased water content after eight days of incubation, with soil saturated by day 19 of the incubation. Persistence of SWR significantly varied with depth, with the highest persistence in the 1–2 cm soil layer. Our findings illustrate that in order to remove SWR, without the effect of chemical surfactants, first microbial degradation of the molecules attributing to SWR has to occur. This indicates a biological mechanism as the driver for non-reversible SWR breakdown rather than a solely physical process.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 June 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 344〈/p〉 〈p〉Author(s): Xinghang Lu, Ruiping Li, Haibin Shi, Jiancai Liang, Qingfeng Miao, Leilei Fan〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this study, the variation of the soil water-heat-salt transport for one whole year of agriculture under different mulching treatments and autumn irrigation in the Hetao Irrigation District of Inner Mongolia has been investigated and the best mulching treatment with the optimal mulching amount for this district have been determined. Based on field tests conducted between October 2013 and October 2015, the field test data of October 2013~October 2014 have been used to calibrate the SHAW model. After the calibration, the model has been used to simulate the soil water-heat-salt transport in the freezing-thawing and growth periods for one whole year of agriculture from October 2014 to October 2015. The accuracy of the model simulations were validated by comparing the simulated results with the field test data. Further, the calibrated SHAW model was used to simulate the process of soil water- salt transport for one whole year of agriculture from October 2015 to October 2016 to assess different mulching treatments. According to the results: ① the simulated soil temperature by the SHAW model is highly accurate, with increasing soil depth, 〈em〉RMSE〈/em〉 decreases and 〈em〉NS〈/em〉 approaches 1. For the simulated soil moisture content, the variations of the simulated and measured soil moisture contents are close to each other. For the simulated soil salinity, the analyses of the simulated and observed soil salinities show that the mean 〈em〉RMSE〈/em〉 for the F0.9 treatment is 0.358 g/kg, and the mean NS is 0.813. Thus, the soil salinity simulation for the straw mulching F0.9 treatment is slightly better than that other treatment. ② Based on a comprehensive analysis on the simulated soil water-salt movement, the best mulching treatment for the Shahao Canal Test Station in the Hetao Irrigation District of Inner Mongolia is the straw mulching with 0.9kg/m〈sup〉2〈/sup〉 mulching amount. The results of this study can be used as a theoretical basis and technical reference for the applications of water-saving autumn irrigation techniques in the Hetao Irrigation District of Inner Mongolia.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 June 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 344〈/p〉 〈p〉Author(s): Qian Fang, Hanlie Hong, Thomas J. Algeo, Xianyu Huang, Angela Sun, G. Jock Churchman, Jon Chorover, Shuling Chen, Yao Liu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Local topography and elevation gradients can exert important influences on soil formation processes such as elemental migration, mineral weathering, and soil organic matter (SOM) accumulation, yet these influences remain insufficiently investigated to date, particularly in surface soils of subtropical monsoonal regions. Here, we report on an investigation of a series of surface soils collected from four different topographic locations across the subalpine Dajiuhu Critical Zone Observatory (CZO), representing hillslope (planar), swale and river channel (convergent), and bulge (divergent) microtopographic sites. Evidence provided by rare-earth element (REE) patterns, immobile element ratios, clay-mineral compositions, and particle-size distributions suggests that these soils have rather uniform parent materials. X-ray diffraction (XRD) analysis revealed that secondary clay minerals in these soils are complex, being dominated by various interstratified clays. Diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy shows similar patterns among the swale, bulge, and river-channel soils that differ from those of the hillslope soils. Most soils at convergent sites with poor drainage contain more smectitic clays (interstratified illite/smectite and chlorite/smectite) and less vermiculitic clays (hydroxyl-interlayered vermiculite and interstratified illite/hydroxyl-interlayered vermiculite), and exhibit weaker chemical weathering and fewer elemental losses than those from non-convergent sites. The diversity of clay types can be ascribed to the complexity and heterogeneity, in particular of pH and hydrology, in these soil environments. Across the range of microtopographic sites investigated here, elemental migration and chemical weathering are generally coupled, with greater elemental losses associated with more intense chemical weathering. Soil organic carbon (SOC) content generally increases at higher elevations, which is attributable to lower temperatures and a consequent reduction of microbial remineralization, and under more reducing soil water conditions. Though influenced by eolian dust, variations in Fe/Mn, Ce anomaly, and C〈sub〉org〈/sub〉/P can reflect redox conditions of different soils. SOC retention is also closely associated with soil redox status, with more reducing conditions being more conducive to SOC preservation.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 June 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 343〈/p〉 〈p〉Author(s): 〈/p〉

Description: 〈p〉Publication date: 15 June 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 344〈/p〉 〈p〉Author(s): Mengfan Li, Jing Wang, Ding Guo, Ruirui Yang, Hua Fu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) are important components of dissolved organic matter (DOM) in soil. A change in the concentration of soil DOM leads to changes in the soil carbon (C) and nitrogen (N) pools and the emergence of potential pollution. Many studies have reported that the concentrations of soil DOM could be significantly influenced by land management practices. However, the results obtained from these studies are inconsistent, and the effects of environmental factors on the responses of DOM concentrations to such management practices remain unclear. The aims of this study were to: (1) synthesize the available datasets and elucidate the general patterns of changes in soil DOM concentrations in response to different land management practices; and (2) probe how the responses of DOM concentrations to management practices were affected by environmental factors (〈em〉e.g.〈/em〉, altitude, climate, and soil properties). Data from 942 observations in 184 publications were collected, integrated, and statistically analyzed. The meta-analysis result shows that overall, N fertilization, liming, organic amendment addition, and vegetation cover significantly increased the concentrations of soil DOM, whereas tillage decreased DOC concentrations. The magnitude of all positive and negative effects was driven by implemented management practices. Generally, a threshold range might exist for the application rate and duration of the management measures that could cause significant changes in DOM concentrations. In addition, DOC concentrations were more responsive to N fertilization and liming than were DON concentrations, indicating that the changes in the two variables were not correlated in each management practice. The results also indicate that the responses of DOM concentrations to management practices could be regulated by the altitude, climate (〈em〉e.g.〈/em〉, mean annual temperature and precipitation), and soil property factors (〈em〉e.g.〈/em〉, total C, total N, C:N ratio, clay content, and initial soil pH). In conclusion, our study suggests that in order to maintain proper soil DOM concentrations in an ecosystem, not only the type and implementation of management practices but also the local environmental factors should be considered when proposing a land management plan.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 8 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma〈/p〉 〈p〉Author(s): Yunzhao Li, Jisong Yang, Miao Yu, Wei Zhao, Ying Xiao, Di Zhou, Chao Zhan, Yang Yu, Jingjing Zhang, Zhenbo Lv, Junbao Yu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉NaCl and Na〈sub〉2〈/sub〉SO〈sub〉4〈/sub〉 salts often dominate in estuarine wetland soils. However, it is unclear how different salt types affect carbon mineralization as a response to salinity levels. In this study, soil samples (0–13 cm) collected in the Liaohe estuarine wetland were amended with NaCl and Na〈sub〉2〈/sub〉SO〈sub〉4〈/sub〉 salts at five salt levels: 1 mS·cm〈sup〉−1〈/sup〉 (EC1), 3 mS·cm〈sup〉−1〈/sup〉 (EC3), 5 mS·cm〈sup〉−1〈/sup〉 (EC5), 10 mS·cm〈sup〉−1〈/sup〉 (EC10) and 18 mS·cm〈sup〉−1〈/sup〉 (EC18). The amended soils were incubated for 193 d, and the carbon mineralization rates were periodically measured. NaCl has decreased carbon mineralization at all salinity levels, but the effect of Na〈sub〉2〈/sub〉SO〈sub〉4〈/sub〉 was found only in the high salinity level (EC18). We found a significant ion-specific effect of salt types on carbon mineralization at the lower salinity levels (EC1, EC3 and EC5) but no significant ion-specific effect at the higher salinity levels (EC10 and EC18). The salt effects highly varied with incubation time and the time changes were depended on salt types. The results suggest that there may be a salinity threshold (5–10 mS·cm〈sup〉−1〈/sup〉) that impacts the ion-specific effect (NaCl and Na〈sub〉2〈/sub〉SO〈sub〉4〈/sub〉) on carbon mineralization, depending on the salinity level and the ionic physiochemical behaviors.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 June 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 344〈/p〉 〈p〉Author(s): Jaakko Heikkinen, Riikka Keskinen, Helena Soinne, Jari Hyväluoma, Johanna Nikama, Hanne Wikberg, Anssi Källi, Virpi Siipola, Thierry Melkior, Capucine Dupont, Matthieu Campargue, Sylvia H. Larsson, Markus Hannula, Kimmo Rasa〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉Various thermochemical conversion technologies can be applied in producing biochar from a wide range of raw materials. We studied the chemical quality of 10 different biochars produced via torrefaction (TOR), slow pyrolysis (SP), or hydrothermal carbonization (HTC), in order to assess their potential in improving clay soil aggregate stability and thus contribute to mitigation of erosion from agricultural soils. X-ray tomography was used to visualize soil aggregates in some selected biochar treatments.〈/p〉 〈p〉Feedstock type had a major influence on the properties of the biochar, but in general biochars derived through SP were alkaline and exhibited higher electrical conductivity and ash content and lower surface activity than acidic HTC and TOR biochars. Alkyl peak areas determined from FTIR spectra were higher in biochars produced by TOR and HTC than in SP biochars, which indicates a higher degree of hydrophobicity in the former. Significantly higher aggregate stability and reduced colloid detachment were achieved with HTC biochars, most likely due to hydrophobicity reducing wetting rate and aggregate slaking.〈/p〉 〈p〉When mixed with initially aggregated soil, the biochar particles settled in inter-aggregate voids. According to image analysis, the internal porosity of soil aggregates was not affected by biochar addition, i.e., biochar did not enter the aggregates during the short incubation period. Addition of hydrophobic HTC biochar decreased the soil water content at field capacity, whereas more inert SP chars tended to increase it. The overall effect of biochar hydrophobicity on soil functions needs to be explored prior to wider use of biochar as a soil amendment.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 June 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 344〈/p〉 〈p〉Author(s): Zahra Rasaei, Patrick Bogaert〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉In a spatial mapping context, we address in this paper the issue of combining at best soil data coming from legacy soil surveys with soil information that is indirectly obtained from remote sensing (RS). We show first how spatial scale issues need to beproperly addressed for soil mapping in order to increase the predictive performances of spatial prediction models, where the two prediction techniques that are compared here are kriging and random forests (RF). By relying afterwards on a Bayesian data fusion approach, we then emphasize the benefit of combining the output of these two prediction models in order to get a single prediction result that leads to an improved final map.〈/p〉 〈p〉The advocated methodology is illustrated with the mapping of soil saturation percentage (SP) over a 10,480 km〈sup〉2〈/sup〉 area located in Iran, were SP is a key soil parameter for sustainable development and land management. A set of 396 soil profiles were obtained from legacy soil surveys and were used to compute vertically averaged SP values. In parallel, a set of RS covariates were obtained from a 90 meters resolution Landsat image and a digital elevation model. Based on the modeling of the spatialdependence both for soil SP data and for RS covariates, it is shown how the relationship between them is improved by using a filtered kriging technique that allows us to focus on their long range component only. Using these filtered SP value and RS covariates, predictions were obtained separately from kriging and from a RF model at the nodes of a 90 meters resolution grid. Even if the performances of these two models are almost identical with 〈em〉R〈/em〉〈sup〉2〈/sup〉 values equal to 0.66–0.67, it is shown afterwards that a Bayesian data fusion procedure that combines both predictions yields improved performance with a 〈em〉R〈/em〉〈sup〉2〈/sup〉 value equal to 0.86. These results clearly emphasize the importance of properly addressing scale issues and the benefit of data fusion inorder to improve the quality of the final map. Though the study was conducted here for SP values, we believe this methodology and these findings are relevant when it comes to handle other soil properties in a spatial mapping context that involves several data sources.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 June 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 343〈/p〉 〈p〉Author(s): Daniel Kyalo Willy, Milu Muyanga, Joseph Mbuvi, Thomas Jayne〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The current study seeks to assess sustainability of agricultural land use by identifying the effect of land use change on soil quality using cross-sectional data collected through a household survey among 525 farm households in densely populated areas of Kenya. Soil samples were collected, analyzed and compared across three land use types: undisturbed, semi-disturbed and cultivated. To achieve these objectives, descriptive, Nutrient Index approach and Classification and Regression Tree (CART) analysis methods were used. Results indicate that within a period of five decades, agricultural land use has led to a decline in Total Organic Carbon (−72%), Magnesium (−65%) and Boron (−61%), Iron (−22%) and Total Nitrogen (−15%). The drivers of deterioration identified were cutting across inherent properties such as soil chemical (pH), physical (soil mapping unit) and biological (organic carbon) attributes, farmer practices (agricultural commercialization) and exogenous factors (population density and Agro-ecological zones). The study concludes that indeed conversion of land from natural vegetation is associated with deterioration in soil quality and therefore policy needs to create incentives for the build-up of soil organic matter, replenishment of soil macro and micro nutrients. Blending of commercial fertilizers with targeted micro-nutrients, maintenance of soil conservation techniques and long term fallowing are encouraged.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 June 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 344〈/p〉 〈p〉Author(s): Cícero Célio de Figueiredo, Jhon Kenedy Moura Chagas, Juscimar da Silva, Jorge Paz-Ferreiro〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The production of biochar is a technological alternative to transform sewage sludge (SS) into a useful product for agro-environmental purposes. Despite an increased knowledge on the role of sewage sludge biochar (SSB) for improving soil quality and crop productivity, some concerns remain regarding the accumulation of total and available heavy metals (HM) in soils amended with SSB. Particularly, there is a dearth of studies under field conditions and in tropical latitudes. Therefore, the objective of this study was to evaluate the effect of applying SS biochars, prepared at different pyrolysis temperatures, on the accumulation and availability of heavy metals (HM). To do so, 15 Mg ha〈sup〉−1〈/sup〉 of SS biochar produced at 300 °C (BC300) and 500 °C (BC500) were applied to a soil cultivated with corn. Total and available levels of HM in SS, biochars and post-harvest soil were determined. Pyrolysis concentrated total HM in the biochars in relation to the SS. However, HM availability was reduced with increasing pyrolysis temperature due to an increase in pH, pore volume, specific surface area, P and K content, and reduction of the H/C ratio. Biochar did not alter the total HM contents, with the exception of Mn. Available levels of all HM in the soil were 〈1.2% of the total contents. In addition, the available levels of Zn and Mn, when evaluated as micronutrients, were considered low. Therefore, the results of the present study indicate that biochar produced from SS of a sewage treatment plant processing predominantly domestic sewage can be used in agriculture, without risk of soil contamination by HM. Moreover, in some tropical soils, with a low value of micronutrients, biochar can provide a source of these elements.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 9 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma〈/p〉 〈p〉Author(s): Yoshie Yageta, Henny Osbahr, Yasuyuki Morimoto, Joanna Clark〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉Soil fertility is vital for agricultural productivity, yet poor soils and erosion remain a management challenge in many parts of sub-Saharan Africa. One challenge is that soil scientists and farmers often evaluate soil fertility using different knowledge systems and the implications have not been clearly reconciled within the literature. In particular, whether farmers are observing similar aspects of structure and function as classified in soil science. If so, what can we learn about how soil fertility is evaluated and communicated in terms of developing a hybrid approach that improves communication of ideas between different stakeholders. This paper addresses this challenge by examining the similarities and differences between farmers' qualitative evaluation and soil science quantitative analysis for soil fertility classification, and how location of soils influence farmers' evaluation of soil fertility. Empirical fieldwork was carried out in two villages in Kitui County, Kenya with 60 farmers using semi-structured interviews and focus group discussion. Based on farmer perception, 116 soil samples of the best and worst soil fertility taken and analysed for physiochemical factors. Farmers had a consistent classification system and primarily relied on texture and colour as indicators for good soil fertility and texture alone for poor soils.〈/p〉 〈p〉Soils with fine texture under the local semi-arid climate were associated with higher pH, TOC and WHC and fertile black and red soils were associated with pH, TOC, WHC and AP based on differences in bed rock. Poor soil fertility was associated with sandy soils and soils with no colour in their local name. Spatial location is an important consideration in farmers' evaluations, reflecting awareness of local diversity in soil and historical social or environmental factors. Local historical narratives reveal the importance in changes to humus, consistent with technical knowledge about the role of soil organic matter for soil fertility. The paper provides a better understanding of farmers' soil classification, evaluation processes and perspectives that help to inform scientists working with alternative frameworks for assessment and, in doing so, supports the development of local tailor-made soil assessment systems.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 June 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 344〈/p〉 〈p〉Author(s): N.S. Wimalathunge, T.F.A. Bishop〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉A confluence of scientific and technological developments in geospatial data have made it possible to parameterise the components of the soil water balance equation in space and time at spatial and temporal resolutions useful for agriculture. In this work, we present results on the development of an approach that takes advantage of this opportunity to predict soil moisture at a spatial resolution of 90 m on a daily time step at multiple depths in the profile.〈/p〉 〈p〉Three types of water balance model were examined: (i) single layer model with saturated flow (ii) multi-layer model with saturated flow and (iii) multi-layer model with unsaturated flow. Five layers were considered: 0–5, 5–15, 15–30, 30–60, and 60–100 cm, which coincide with the layers of the Soil Landscape Grid of Australia which is available at ~90 m spatial resolution. Pedotransfer functions were used to predict the bucket size for each soil layer. Precipitation and evapotranspiration are estimated by gridded SILO precipitation data (5 km, 1 day) and the MODIS 16 ET product (1 km, 8 day), respectively. Soil moisture predictions were tested against four publicly and privately owned soil moisture networks.〈/p〉 〈p〉The multi-layer model incorporating unsaturated flow performed the best in terms of predicting soil moisture for the whole profile (0–1 m) with a median correlation coefficient (r) of just over 0.7 across all sites. When classifying the sites according to the land use; cropping sites showed better median correlation (~0.8) than grazing sites (~0.7). However, grazing sites seem to have more consistent results for all the layers. To understand the relative importance of the water balance model predictions as compared to other environmental properties, a Random Forest model was fitted to a suite of variables 〈em〉e.g.〈/em〉 soil order, month, temperature and 〈em〉etc.〈/em〉, that vary in space, time or both space and time. For the analysis, only calibrated soil moisture network sites (OzNet) were considered. Soil moisture which was derived from unsaturated soil water balance model was the 9th most important variable. To assess the quality of the predictive model, leave-one-out-site cross validation (LOOSCV) was performed and across all sites the prediction quality was reasonable (Concordance = 0.66, Accuracy = 0.06 cm 3 cm〈sup〉−3〈/sup〉). These results highlight the potential of this approach and since it is based on readily available data it is scalable to large spatial domains.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 July 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 345〈/p〉 〈p〉Author(s): Dasheng Sun, Xinbing Yang, Chunling Wang, Xianjun Hao, Jianping Hong, Xianyong Lin〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Freeze-thaw cycles strongly affect the transformation of soil phosphorus (P) and shape the composition of P pools. This study aimed to investigate the effects of successive freeze-thaw cycles on the transformation of soil labile P and enzymatically hydrolysable organic P (Po) fractions. Accordingly, five physico-chemically distinct soils were subjected to two, five, and ten freeze-thaw cycles, with each cycle including incubation at −10 °C (freeze) for 12 h and 5 °C (thaw) for 12 h. Control soils were maintained at 5 °C, and the bicarbonate-extractable P and hydrolysable P〈sub〉o〈/sub〉 fractions were analysed at the end of the incubation period (10 d). Freeze-thaw cycles increased the levels of bicarbonate-extractable inorganic P, bicarbonate-extractable P〈sub〉o〈/sub〉, labile monoester P, and phytate-like P, but had no effect on the diester P and unknown P〈sub〉o〈/sub〉 contents. The interaction between soil type and freeze-thaw cycles significantly affected the NaHCO〈sub〉3〈/sub〉-extractable P〈sub〉i〈/sub〉, and phytate-like P fractions, but did not affect the bicarbonate-extractable P〈sub〉o〈/sub〉, and labile monoester P fractions. The extent of increase in NaHCO〈sub〉3〈/sub〉-extractable P〈sub〉i〈/sub〉 largely depended on the amount of organic matter in the soil. In most cases, bicarbonate-extractable P and hydrolysable P〈sub〉o〈/sub〉 fractions reached their maximum levels after two freeze-thaw cycles and declined or remained constant thereafter. Our results suggest that freeze-thaw cycles exacerbated the transformation of soil labile P fractions, including enzymatically hydrolysable P〈sub〉o〈/sub〉 species, especially in the earlier stages.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 June 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 344〈/p〉 〈p〉Author(s): Ilan Stavi, Yulia Gusarov, Rares Halbac-Cotoara-Zamfir〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Water is the major limiting factor for primary productivity in drylands. In ancient times, stone terraces aimed at runoff harvesting and soil erosion control were established, allowing agricultural crop production. Land abandonment and cease of maintenance have led to the collapse and failure of terraces in the hinterlands of the Roman/Byzantine city of Avdat in the arid Negev Desert, Israel. The objective of this study was to assess the geomorphic processes and pedogenic mechanisms related to terrace collapse, and their on-site impact on soil quality. We studied key properties of the top 10 cm of soil in intact-terrace plots and partially-collapsed terrace plots, as well as in ‘natural’ lands. Unexpectedly, the soil texture was finer in the partially collapsed-terrace plots (clay loam) than that in the intact-terrace plots (loam). This was attributed to transportation of mineral material by rolling, which sorts out the large primary particles. This process, which characterizes rill erosion of high erosive power, is probably the predominant surface process in this study. The soil penetration resistance was significantly greater in the partially-collapsed terrace plots, and was attributed to the continuous removal of recently deposited loose sediments and exposure of the underlying, compacted older sediments. Soil stoniness, which was 16-fold greater in the partially-collapsed terrace plots, was also attributed to soil erosion. Unexpectedly, the total organic carbon was similar in both terrace states. Yet, labile organic carbon was 41% lower in soil of the partially-collapsed terrace plots, suggesting greater susceptibility of this fraction to erosional processes. The low electrical conductivity in the soil of the intact-terrace plots, was attributed to the better leaching of salts. The soil's calculated available water capacity was 42% greater in the intact-terrace plots. The study suggests that these processes and mechanisms strengthen each other through a chain of feedbacks, resulting in accelerated degradation of the collapsed-terrace lands.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0016706118324200-ga1.jpg" width="301" alt="Unlabelled Image" title="Unlabelled Image"〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 June 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 344〈/p〉 〈p〉Author(s): Laura Giagnoni, Anita Maienza, Silvia Baronti, Francesco Primo Vaccari, Lorenzo Genesio, Cosimo Taiti, Tania Martellini, Roberto Scodellini, Alessandra Cincinelli, Corrado Costa, Stefano Mancuso, Giancarlo Renella〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The agronomic management of vineyards, aimed at the maximization of grape yields, is intensive and includes repeated tillage, crop residues removal, strict weed and pest control treatments. In viticulture, healthy soils and a suitable climate are the key factors that influence the quality of the produced wine. Even under intensive agronomic practices, typical of conventional viticulture, the choice of appropriate soil management strategies can preserve soil quality in the long term. The use of biochar as soil amendment has been suggested as a potential practice that allows restoration of the functionality of degraded soils in terms of water retention, chemical and biological fertility. In this paper we report the results of a long field trial on biochar amendment of a vineyard, assessing the impact on soil functionality, VOC emission and fertility. Our results show that biochar effects on soil functions and fertility are maintained in the long term (seven years) after a one-time application.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 June 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 344〈/p〉 〈p〉Author(s): Zi-Qiang Yuan, Chao Fang, Rong Zhang, Feng-Min Li, Muhammad Mansoor Javaid, Ivan A. Janssens〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Lucerne (〈em〉Medicago sativa〈/em〉 L.) is widely planted on the semi-arid Loess Plateau in China to control soil erosion, yet the extent to which topography affects the productivity of lucerne still remains poorly understood. This study aimed to evaluate how topographic position influences soil properties and aboveground biomass in lucerne-rich vegetation. A total of 112 quadrats were established in 28 fields covered with 11-year-old lucerne vegetation. In each quadrat, the slope, slope position, slope aspect, altitude, soil properties (soil moisture content, organic carbon, total nitrogen [N] and phosphorus [P], available P and inorganic N), and aboveground biomass were measured. Redundancy and multiple regression analyses were performed to determine the relationships among topographic factors, soil properties and aboveground biomass. A modest proportion of variation in soil variables was explained by topographic variables. The altitude, slope and slope position, rather than the slope aspect, were the key factors that influencing soil variables. Soil organic carbon, total N, inorganic N, the ratio of organic carbon to available P (C/P), and the ratio of total N to available P were positively correlated with altitude, whereas available P was negatively correlated with altitude. The soil moisture content was primarily affected by the slope and slope position. The topographic factors did not directly affect the total and lucerne aboveground biomass. The total and lucerne aboveground biomass were positively correlated to soil moisture content, inorganic N and C/P. Therefore, the aboveground biomass of lucerne-rich vegetation could be indirectly regulated by the slope and slope position through the effect on the soil moisture content and by altitude through the effect on soil inorganic N and C/P. This work highlighted the importance of soil properties such as soil moisture and P dynamics in the revegetation process of lucerne in this semi-arid region. As soil properties can be directly governed by topography, considering topography could enhance the quality of vegetation restoration in the large hilly region of the Loess Plateau.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 353〈/p〉 〈p〉Author(s): Di He, Enli Wang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Plant available water holding capacity (PAWC) influences the efficiency of rainfall used by crops and consequently crop productivity in dryland cropping systems. However, how soil PAWC interacts with rainfall to determine crop yield has not been quantified systematically. In this study, we used an agricultural production systems model (APSIM) and wheat as an example to quantify crop growth and yield in response to a wide range of soil PAWCs. Results show that wheat yield increased with soil PAWCs following a negative exponential curve. There is a critical PAWC above which PAWC has no impact. A summary model incorporating the impact of soil PAWC, annual rainfall and the fraction of rainfall during growing season together could explain over 95% variations in long-term averaged wheat yield. The results and the summary model provide the scientific basis to systematically explain crop yield variation in response to soil PAWC change across contrasting climates.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 352〈/p〉 〈p〉Author(s): Marija Egerić, Ivana Smičiklas, Biljana Dojčinović, Biljana Sikirić, Mihajlo Jović, Marija Šljivić-Ivanović, Dragan Čakmak〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Liming is a common practice in the treatment of acidic and metal contaminated soils, aiming at pH regulation, enhancing of the nutrient availability and attenuation of trace metals mobility. Replacement of natural limestone with alternative soil alkalizers found among waste materials represents a step towards sustainable resource management and reduced waste storage. In this study, waste seashells (SW) and red mud (RM) were applied in different doses to the soil sampled in the vicinity of mining and smelting complex. The soil was characterized by acidic reaction (pH 4.93), increased Cu concentration (219.2 mg/kg) and a very low level of P-supply (3.61 mg P〈sub〉2〈/sub〉O〈sub〉5〈/sub〉/100 g). The study aimed to quantify and compare additive-induced effects onto soil physicochemical properties, the status of macronutrients and distribution of trace metals. Targeted effect on soil pH was achieved with SW dose of 0.3% and RM dose of 2%. RM was found to be a source of available P and gave rise to the available P concentrations in the soil. Medium level of P-supply (15.60 mg P〈sub〉2〈/sub〉O〈sub〉5〈/sub〉/100 g) was achieved with RM dose of 5%, however, the increase in soil salinity and total trace elements concentrations have become significant adverse effects at such dose. The decrease in the ion-exchangeable content of Cu and other trace metals was in correlation with the increase in soil pH after the treatments. Redistribution of metal cations was mainly directed to carbonate/acid soluble and Fe, Mn-oxide bonded fraction after SW addition. Even though trace metals concentration has increased in the soil after application of the RM, they were principally found in the residual fraction. The results emphasize low amounts of contained trace elements and lower doses for achieving targeted effects on pH and metal mobility as the main benefits of SW treatments. On the other hand, moderate and controlled use of RM may represent multiple benefits in terms of simultaneous pH regulation, P-supply, and reduced trace metals mobility.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0016706119306172-ga1.jpg" width="500" alt="Unlabelled Image" title="Unlabelled Image"〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 352〈/p〉 〈p〉Author(s): Wartini Ng, Budiman Minasny, Maryam Montazerolghaem, Jose Padarian, Richard Ferguson, Scarlett Bailey, Alex B. McBratney〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉No single instrument can characterize all soil properties because soil is a complex material. With the advancement of technology, laboratories have become equipped with various spectrometers. By fusing output from different spectrometers, better prediction outcomes are expected than using any single spectrometer alone. In this study, model performance from a single spectrometer (visible-near-infrared spectroscopy, vis-NIR or mid-infrared spectroscopy, MIR) was compared to the combined spectrometers (vis-NIR and MIR). We selected a total of 14,594 samples from the Kellogg Soil Survey Laboratory (KSSL) database that had both vis-NIR and MIR spectra along with measurements of sand, clay, total C (TC) content, organic C (OC) content, cation exchange capacity (CEC), and pH. The dataset was randomly split into 75% training (〈em〉n〈/em〉 = 10,946) and the remaining (〈em〉n〈/em〉 = 3,648) as a test set. Prediction models were constructed with partial least squares regression (PLSR) and Cubist tree model. Additionally, we explored the use of a deep learning model, the convolutional neural network (CNN). We investigated various ways to feed spectral data to the CNN, either as one-dimensional (1D) data (as a spectrum) or as two-dimensional (2D) data (as a spectrogram). Compared to the PLSR model, we found that the CNN model provides an average improvement prediction of 33–42% using vis-NIR and 30–43% using MIR spectral data input. The relative accuracy improvement of CNN, when compared to the Cubist regression tree model, ranged between 22 and 36% with vis-NIR and 16–27% with MIR spectral data input. Various methods to fuse the vis-NIR and MIR spectral data were explored. We compared the performance of spectral concatenation (for PLSR and Cubist model), two-channel input method, and outer product analysis (OPA) method (for CNN model). We found that the performance of two-channel 1D CNN model was the best (R〈sup〉2〈/sup〉 = 0.95–0.98) followed closely by the OPA with CNN (R〈sup〉2〈/sup〉 = 0.93–0.98), Cubist model with spectral concatenation (R〈sup〉2〈/sup〉〈sup〉 〈/sup〉= 0.91–0.97), two-channel 2D CNN model (R〈sup〉2〈/sup〉 = 0.90–0.95) and PLSR with spectral concatenation (R〈sup〉2〈/sup〉 = 0.87–0.95). Chemometric analysis of spectroscopy data relied on spectral pre-processing methods: such as spectral trimming, baseline correction, smoothing, and normalization before being fed into the model. CNN achieved higher performance than the PLSR and Cubist model without utilizing the pre-processed spectral data. We also found that the predictions using the CNN model retained similar correlations to the actual values in comparison to other models. By doing sensitivity analysis, we identified the important spectral wavelengths variables used by the CNN model to predict various soil properties. CNN is an effective model for modelling soil properties from a large spectral library.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 352〈/p〉 〈p〉Author(s): A. Modaresi Rad, B. Ghahraman, M. Sadegh〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The relation between soil pore structure and water retention is complex and is often not well determined. We present a novel approach based on critical path analysis from percolation theory to refine hydraulic conductivity estimation from soil water retention curve by introducing a new tortuosity parameter as a function of scaling factor. We generalize this model to account for large shifts in the relation between soil pore structure and water retention, which are indicative of soils with multi-fractal properties, by employing a 〈em〉t〈/em〉-test on scaled saturation and suction data. The proposed model relaxes the constraints that were set on model parameters for multi-fractal soils in the literature by tuning “all” parameters against observed data using a multiple-start gradient-based optimization algorithm, and is applicable to a wider variety of soil textures. The optimization results are further evaluated against those of a Markov Chain Monte Carlo algorithm to ensure global optimum is found. Goodness-of-fit (GOF) measures, including geometric mean and standard deviation error ratios, and Nash-Sutcliffe efficiency, show that the proposed model presents less bias across the entire range of matric potential compared to its predecessor that under-estimate hydraulic conductivity in all studied cases.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 352〈/p〉 〈p〉Author(s): Andrea Román-Sánchez, Garry Willgoose, Juan Vicente Giráldez, Adolfo Peña, Tom Vanwalleghem〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉The disintegration of rocks into soil plays an important role in geomorphological processes, such as the evolution of hillslopes and river valleys. Nevertheless, the factors and processes controlling the physical weathering of rock particles are poorly understood. In this study, the surface and subsurface distribution of rock fragments abundance and size is measured in ten soil profiles along three hillslopes transects. For the surface horizons, we observed a significant linear relation between the ninth decile of the diameter, d〈sub〉90〈/sub〉, and hillslope gradient and for both surface and subsurface horizons, a significant logarithmic relation between d〈sub〉90〈/sub〉 and rock fragment abundance. For the first time, the performance of various fragmentation models is compared against field data to evaluate if the surface rock distribution can be explained from fragmentation of the subsurface material only. In six profiles these fragmentation models adequately reproduced the observed particle size distribution. In the other four profiles, all located on eroding hillslopes, armouring dominates over fragmentation and the surface rock distribution is coarser compared to the subsurface. Generally, the profiles have a good fit to almost all models with the exception of two. However, we can differentiate two zones in terms of fragmentation mechanism according to the modelling results. The profiles in the transect located along a gently sloping hillslope, and the two other profiles, along a steep river valley.〈/p〉 〈p〉In the models, we consider physical weathering as the single factor of particle size evolution, except or two models where conceptual chemical weathering of the fine fraction is considered, although this chemical weathering was not specifically designed to explore soil water chemistry or mineralogy in detail. The observed discrepancies between field data and the results of this study, especially in the fine fraction, reveal the possible relevance of chemical or biological weathering, redistribution processes and the lower accuracy of the number of fine fraction classes established and measured than in the coarse fraction for the field data.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 347〈/p〉 〈p〉Author(s): Shengtian Yang, Yabing Guan, Changsen Zhao, Chunbin Zhang, Juan Bai, Ke Chen〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Gully erosion can be a serious threat to ecologic and socio-economic stability. Although gully erosion intensity is highly impacted by catchment area changes, few studies have focused on the relevant mechanisms. This study presents a new approach to studying this issue by combining historic aerial photography and recent unmanned aerial vehicle (UAV) imagery to determine changes in gully morphology over 40 years on China's Loess Plateau, one of the world's most erosion-prone regions. Aerial photographs from 1976 were matched with UAV imagery taken in 2017 to compare gully and surface conditions in two study areas over time. Next, a new method was developed for calculating changes in gully volume and erosion moduli based on the UAV-derived digital surface model. Finally, the impacts of catchment area change on gully erosion moduli over the study period were analyzed. The results showed that the catchment areas decreased by 0.71–77.88%; greater decreases resulted in lower gully erosion moduli (with an exponential correlation) and reducing catchment area effectively slowed gully development. In addition, regional agricultural terrace construction has reduced the catchment areas, in turn reducing the amount of runoff entering gullies and thus reducing incision. Therefore, the management and maintenance of abandoned terraces should be strengthened by local governments and stakeholders to reduce runoff-induced gully erosion and sediment loss from upslope areas. The methodologies and results of this study have the potential to provide significant scientific references for the conservation of runoff and sediment in erosion-prone regions of China and elsewhere.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 347〈/p〉 〈p〉Author(s): Sangeeta Lenka, Pankaj Trivedi, Brajesh Singh, Bhupinder Pal Singh, Elise Pendall, Adrian Bass, Narendra Kumar Lenka〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Priming of soil organic carbon (SOC) is a crucial factor in ecosystem carbon balance. Despite its increasing importance in the changing global climate, the extent of influence of temperature and soil properties on the priming effect remains unclear. Here, soil priming was investigated using 〈sup〉13〈/sup〉C labeled wheat residues in two cultivated, subtropical (Vertisol) and semi-arid (Luvisol), soils of Australia at four incubation temperatures (13, 23, 33 and 43 °C). The priming effect was computed from respired CO〈sub〉2〈/sub〉 and associated δ〈sup〉13〈/sup〉C, which were measured periodically over the 52-day incubation period. Wheat residue addition resulted in greater priming effect in the Luvisol (1.17 to 2.37% of SOC) than the Vertisol (0.02 to 1.56% of SOC). The priming of SOC was the highest at 23 °C in the Luvisol, and at 43 °C in the Vertsiol, which indicates a variable positive priming effect of temperature in different soil types. Wheat residue addition significantly increased the temperature sensitivity (Q〈sub〉10〈/sub〉) of SOC mineralization in the Vertisol at temperature ranges below 33 °C (i.e., 13–23 and 23–33 °C) and had no significant effect in the Luvisol. A negative correlation was observed between temperature and the Q〈sub〉10〈/sub〉 values. Across soils, the Q〈sub〉10〈/sub〉 of residue C was lower than SOC suggesting that soil C is more vulnerable to climatic warming. This work demonstrates that the magnitude of SOC priming by wheat residue and Q〈sub〉10〈/sub〉 of SOC mineralization varied significantly with soil type (Luvsiol 〉 Vertisol) and incubation conditions (temperature and time). Given the current trend towards increasing atmospheric temperatures, future studies should evaluate temperature effects on the priming of different pools of SOC induced by crop residue in different agro-ecosystems.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 353〈/p〉 〈p〉Author(s): Renshan Li, Wenhui Zheng, Qingpeng Yang, Weidong Zhang, Yonggang Chi, Peng Wang, Ming Xu, Xin Guan, Longchi Chen, Qingkui Wang, Silong Wang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Thinning and understory removal are two common silvicultural practices used in plantation ecosystems, and both are expected to influence soil respiration (R〈sub〉S〈/sub〉). However, little is known about how the two practices, particularly their interaction, affect the heterotrophic (R〈sub〉H〈/sub〉) and autotrophic (R〈sub〉A〈/sub〉) components of R〈sub〉S〈/sub〉. This knowledge gap further constrains our accurate evaluation on the carbon balance in plantations upon both thinning and understory removal, because the two practices are often conducted simultaneously in plantation management. Thus, we partitioned R〈sub〉S〈/sub〉 into R〈sub〉H〈/sub〉 and R〈sub〉A〈/sub〉 using trenched plots in a Chinese fir (〈em〉Cunninghamia lanceolata〈/em〉) plantation subject to thinning and understory removal. The R〈sub〉S〈/sub〉 and its two components were measured in 2013 and 2014 at approximately monthly intervals. The potential control factors such as soil temperature, soil moisture and soil chemical properties were also determined. We found that thinning marginally significantly (〈em〉P〈/em〉 = 0.059) increased R〈sub〉S〈/sub〉 in 2013 by 17.32%, while it had no influence on R〈sub〉S〈/sub〉 in 2014 (〈em〉P〈/em〉 〉 0.1), indicating that the influence of thinning on R〈sub〉S〈/sub〉 weakened with time. Similarly, a significant increase in R〈sub〉H〈/sub〉 toward thinning also occurred in 2013 (by 32.5%) but not in 2014. However, R〈sub〉A〈/sub〉 showed no response to thinning in either year. No interaction effect between thinning and understory removal was found on R〈sub〉S〈/sub〉, R〈sub〉H〈/sub〉, and R〈sub〉A〈/sub〉. The increased soil temperature in the thinned stands in 2013 played a key role in raising the post-thinning R〈sub〉H〈/sub〉 and R〈sub〉S〈/sub〉 in this year. Generally, the temperature sensitivity (Q〈sub〉10〈/sub〉) value of R〈sub〉S〈/sub〉 and its components increased in the order of R〈sub〉H〈/sub〉 〈 R〈sub〉S〈/sub〉 〈 R〈sub〉A〈/sub〉 regardless of treatment. The Q〈sub〉10〈/sub〉 value of R〈sub〉S〈/sub〉 showed negligible variation among different treatments, and thus was likely not affected by thinning, understory removal, or their interactions. The results highlighted that understory removal in thinned stands would not exacerbate soil carbon emission in this plantation.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 27 June 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma〈/p〉 〈p〉Author(s): Mogens H. Greve, Luboš Borůvka〈/p〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 353〈/p〉 〈p〉Author(s): Mo Li, Jiang Li, Vijay P. Singh, Qiang Fu, Dong Liu, Gaiqiang Yang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This study proposes an optimization-simulation approach for simultaneously determining crop patterns and allocating irrigation water to improve soil environment. The approach incorporates an optimization model (a Chance-Constrained Programming (CCP) based multi-objective non-linear programming) integrated with a carbon footprint (〈em〉CF〈/em〉) model and irrigation water use efficiency (〈em〉IWUE〈/em〉) index, a soil water balance model and a groundwater dynamics model. The output of the optimization model constitutes the input to the soil water balance model which is calculated based on soil water content from soil samples representing the basin under study, and the resulting output is the input to the groundwater dynamics model. The output of the groundwater dynamics model is examined by whether the optimal results give rise to soil salinization. The proposed approach has advantages in addressing the tradeoffs of land and water resources for different crops in irrigation districts to reduce soil carbon emissions and improve land and water resources allocation efficiency, dynamically reflecting water transformation among precipitation, surface water, soil water and groundwater, and dealing with nonlinearity and uncertainties. The approach was applied to identify optimal land and water resources allocation schemes in the oasis of Heihe River basin, northwest China. Results demonstrated that in the studied area, soil carbon emissions decreased and water use efficiency increased by the simultaneous allocation of the interactive agricultural land and water resources in space and time. Choosing the violation probabilities in the range of 0.05 and 0.1 might be more beneficial to the comprehensive benefits of the contradictory objectives (〈em〉i.e.〈/em〉 reducing soil carbon emissions and increasing irrigation water use efficiency), because during this range the value of 〈em〉IWUE〈/em〉 tended to be the largest and the value of 〈em〉CF〈/em〉 was beginning to stabilize. From the perspective of spatial distribution, the value of 〈em〉CF〈/em〉 showed an increasing trend from northwest to southeast, while the changes of groundwater table in the southern part were higher than in the northern part of the oasis. As the main limiting factor, increasing water availability led to an increase of cultivated land within a certain range, which significantly affected soil environment, leading to the necessity to contribute towards the efficient utilization of irrigation water resources and field activities to reduce soil pollution. Therefore, the proposed modelling framework can help to comprehensively manage agricultural land and water resources under complexity in an efficient and environmental-friendly way, and thus promote soil environment protection.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 353〈/p〉 〈p〉Author(s): Shuo Jiao, Qiaoping Li, Xiaoyu Zai, Xuee Gao, Gehong Wei, Weimin Chen〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Determining the mechanisms underlying complex plant-microbe interactions and feedbacks is crucial for effective rhizoremediation of contaminated soils. Here, rhizosphere bacterial communities of 10 common legumes planted in arable and aged oil-contaminated soils for 90 days were used to degrade phenanthrene (PHE). Bacterial community structures were analyzed to reveal the mechanisms underlying the varying PHE degradation capacities. We found that bacterial 〈em〉β〈/em〉-diversity within the rhizospheres played a major role in predicting PHE degradation rates, and more complex bacterial communities exhibited higher PHE degradation capacities. The highest PHE degradation rates were obtained with bacterial communities of 〈em〉Coronilla varia〈/em〉 and 〈em〉Vigna unguiculata〈/em〉 planted in oil-contaminated soils (almost 80%). There were significant differences in bacterial community composition between arable and contaminated soils, and among different legumes rhizospheres and the unplanted soils, although minimal differences were observed in bacterial 〈em〉α〈/em〉-diversity. The potential degradation-related taxa were more abundant in bacterial communities from contaminated soils, indicating more effective PHE degradation than in arable soils. Network analysis revealed the vital ecological roles of the potential degradation-related taxa in the maintenance of complex associations among bacterial taxa. Oil contamination reduced the differences in bacterial community composition between rhizosphere soils with high and low PHE degradation rates. These results suggest that the formulation of effective rhizoremediation strategies ought to focus on more diverse and complex interactions between rhizosphere-inhabiting organisms from aged oil-contaminated soils through the selection of optimal plant-microbiota association.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 20 June 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma〈/p〉 〈p〉Author(s): Sushil Lamichhane, Lalit Kumar, Brian Wilson〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This article reviews the current research and applications of various digital soil mapping (DSM) techniques used to map Soil Organic Carbon (SOC) concentration and stocks following a systematic mapping approach from 2013 until present (18 February 2019). It is intended that this review of relevant literature will assist prospective researchers by identifying knowledge clusters and gaps in relation to the digital mapping of SOC. Of 120 studies, most were clustered in some specific countries such as China, Australia and the USA. The highest number publications were in 2016 and 2017. Regarding the predictive models, there was a progression from Linear Models towards Machine Learning (ML) techniques, and hybrid models in Regression Kriging (RK) framework performed better than individual models. Multiple Linear Regression (MLR) was the most frequently used method for predicting SOC, although it was outperformed by other ML techniques in most studies. Random Forest (RF) was found to perform better than MLR and other ML techniques in most comparative studies. Other common and competitive techniques were Cubist, Neural Network (NN), Boosted Regression Tree (BRT), Support Vector Machine (SVM) and Geographically Weighted Regression (GWR). Due to the inconsistency in various comparative studies, it would be advisable to calibrate the competitive algorithms using specific experimental datasets. This review also reveals the environmental covariates that have been identified as the most important by RF technique in recent years in regard to digital mapping of SOC, which may assist in selecting optimum sets of environmental covariates for mapping SOC. Covariates representing organism/organic activities were among the most frequent among top five covariates, followed by the variables representing climate and topography. Climate was reported to be influential in determining the variation in SOC level at regional scales, followed by parent materials, topography and land use. However, for mapping at a resolution that represents smaller areas such as a farm- or plot-scale, land use and vegetation indices were stated to be more influential in predicting SOC. Furthermore, unlike a previous review work, all recent studies in this review incorporated validation and 41% of them estimated spatially explicit prediction of uncertainty. Only 9.16% studies performed external validation, whereas most studies used data-splitting and cross-validation techniques which may not be the best options for datasets obtained through non-probability sampling.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 352〈/p〉 〈p〉Author(s): Jun-Jian Wang, Ze-Rui Liu, Shi-Qiang Wan, Hong-Yan Han, Wen-Zhou Zhu, Zi-Ting Zhang, Wan-Ling Huang, Hui Zeng〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Global change is increasingly recognized as a possible regulator of metal(loid) biogeochemistry, but it is not well known whether and to what extent multiple environmental change factors alter the metal(loid) levels in surface soils. Here, we analyzed the total concentrations of surface soil metal(loid)s (Ca, Mn, Cr, V, Pb, Ni, Cu, Co, As, and Cd) with 3 years of simulated warming, increased precipitation, nitrogen addition, and elevated CO〈sub〉2〈/sub〉, and with 9 years of simulated warming and increased precipitation, both in the Inner Mongolia steppe (northern China). Three relatively mobile fractions of the metal(loids), i.e., exchangeable, carbonate, and organic-bound fractions, were also quantified. Results showed that multiple environmental change factors had antagonistic interactions on only a few number of total or fractional metal(loid) concentrations. The antagonistic interactions between nitrogen addition and elevated CO〈sub〉2〈/sub〉 on some metal(loid) concentrations suggest that the significant simple effects of N addition without elevated CO〈sub〉2〈/sub〉 treatment reported here or previously may not happen with a future, higher CO〈sub〉2〈/sub〉 level. The main effects of all 3- or 9-years of treatments on total or fractional metal(loid) concentrations in surface soils were all no more than 25%. These findings indicate that global environmental change has a relatively weak impact on surface soil metal(loid) pools and the associated ecological risks in the Inner Mongolia steppe at a near-decadal scale.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S001670611832425X-ga1.jpg" width="356" alt="Unlabelled Image" title="Unlabelled Image"〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 352〈/p〉 〈p〉Author(s): Izabela Jośko, Patryk Oleszczuk, Joanna Dobrzyńska, Barbara Futa, Jolanta Joniec, Ryszard Dobrowolski〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The growth of the nanoproduct market results in the abundance of engineered nanoparticles (ENPs) in the environment, including soils. The very important step regarding to the presence of ENPs in the soil is the evaluation of ENPs effect on the soil microbial community. In the presented study the impact of nano-CuO and nano-ZnO (at 10 mg kg〈sup〉−1〈/sup〉) on dehydrogenase activity, the numbers of fungi and of oligo and copiotrophic bacteria was investigated at the 1, 90, 730 days after application of ENPs to soils. The concentrations of water-soluble and CHCl〈sub〉3〈/sub〉-labile Cu and Zn in the soil samples were also determined. In most cases, the dehydrogenase activity and the number of bacteria and fungi was different in treated and untreated soil, especially after 1 and 90 days of incubation. The effects of ENPs on the soil microbial community could be related to the different concentration of metals in water soluble fraction. The decrease of Zn and Cu concentrations did not always mean a reduction of the effect of ENPs on the microbial community, which could have been related with the different species composition of the microorganisms and their tolerance and capability of adaptation to the presence of ENPs. We also observed that a long-term exposure of the soil microflora to investigated ENPs did not cause any significant changes in the enzymatic activity and in the size of population of the tested group of microorganisms. Similarly to microbiological indicators, the level of water soluble metal concentration in treated and untreated soil did not differ after 730 days.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0016706119303258-ga1.jpg" width="301" alt="Unlabelled Image" title="Unlabelled Image"〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 347〈/p〉 〈p〉Author(s): M. Taufik, A.A. Veldhuizen, J.H.M. Wösten, H.A.J. van Lanen〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Widespread degradation of Indonesian peatlands by deforestation and excessive drainage results into more frequent fires, particularly in El Niño years, which causes: (i) release of enormous amounts of peat soil carbon to the atmosphere, impacting climate, (ii) severe air pollution, affecting human health and air traffic, and (iii) decreased ecosystem services through loss of biodiversity. Groundwater table decline is the main driver of these negative processes and, therefore restoration of peatland hydrology is essential. Although groundwater table depth is critical to counteract peatland degradation, optimal depths are not generic for all peatlands, but depend on peat physical properties (i.e. water retention, unsaturated conductivity), which are related to the degree of peat humification (Fibric, Hemic, Sapric). Unfortunately only few of these peat physical properties are available while they are essential input data in hydrological models required to extend the usually short observed groundwater hydrographs. An experiment with the Soil-Water-Atmosphere-Plant model (SWAP) for two locations in Indonesian peatlands illustrates the impact of the degree of peat humification on physical properties and thereby on calculated groundwater table depth, hydrological drought and associated fires hazards. The Variable Threshold Method is applied to convert groundwater table depths into hydrological drought, and next the modified Keetch-Byram Drought Index (〈em〉mKBDI〈/em〉) is used to assess wildfire hazard. Peat physical properties that reflect higher peat humification (Hemic and Sapric) result into lower water tables during dry periods, in particular during El Niño years, more severe hydrological drought, and an earlier and longer fire season. Using the limited available peat physical properties the importance is demonstrated of initiating a comprehensive programme to build a database of peat physical properties covering different environmental conditions in which tropical peatlands occur. Availability of such a database connected to a long-term monitoring programme, will support the ongoing rewetting, revegetation and revitalisation programme for Indonesian peatlands, which eventually will contribute to sustainable livelihoods for local people and reduce impact on the regional climate.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 347〈/p〉 〈p〉Author(s): Travis W. Nauman, Michael C. Duniway〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Fine scale maps of soil properties enable efficient land management and inform earth system models. Recent efforts to create soil property maps from field observations tend to use similar tree-based machine learning interpolation approaches, but often deal with depth of predictions, validation, and uncertainty differently. One of the main differences in approaches is whether to model individual depths of interest separately as ‘2D’ models, or to create models that incorporate depth as a predictor variable creating a ‘3D’ model that can make predictions for all depths. It is unclear how choice of 2D or 3D approach influences model accuracy and uncertainty due to lack of direct comparison and inconsistent presentation of results in past studies. This study compares 2D and 3D methods for mapping soil electrical conductivity (salinity), pH, sum of fine and very fine sands, and organic carbon at 30 m resolution for the upper 432,000 km〈sup〉2〈/sup〉 of the Colorado River Watershed of the United States of America. A new, simple, model-agnostic relative prediction interval (RPI) approach to report uncertainty is presented that scales prediction interval width to the 95% interquantile width of the original training sample distribution. The RPI approach enables direct comparison of uncertainty between properties and depths and is easily interpretable by end users. Results indicate that 3D mapping of soil properties with strong variation with depth can result in substantial areas with much higher uncertainty that coincide with unrealistic predictions relative to 2D models, even though 3D models had slightly better global cross-validation scores. Maps and global model summaries of RPI proved helpful in identifying these issues with 3D models. These results suggest that the use of RPI or similar approaches to evaluate models can identify accuracy problems not evident in global validation diagnostics.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 347〈/p〉 〈p〉Author(s): Jean Cheyson Barros dos Santos, Emilia Le Pera, Cybelle Souza de Oliveira, Valdomiro Severino de Souza Júnior, Fabrício de Araújo Pedron, Marcelo Metri Corrêa, Antonio Carlos de Azevedo〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Rare earth elements (REEs) are a group of elements (from La to Lu) with high economic value and serve mainly as essential raw material for various high-technology items. This study explores mineral weathering and the geochemical evolution of regoliths (quaternary period) derived from orthogneisses (late Cretaceous Period) in four sites in Borborema Province, NE Brazil, providing a new contribution to the understanding of the influence of soil and saprolite attributes on the distribution of REEs in the regolith. We used optical and electron microscopy to depict the weathering of minerals in the rock, saprolite and soil microstructure, focusing on the distribution of REEs in the regolith (Depth: 3.0 m). We also determined the poorly and well-crystallized iron oxide contents, the clay fraction amount and the total organic carbon content to observe how these attributes influence the distribution of REEs in the soil and saprolite. The results allowed the classification of weathering for feldspars, micas and other primary minerals into four stages based on their degree of alteration and the consequent influence on the geochemistry of the regoliths. Advancement of the weathering stages revealed the relative increases in Fe and Ti compared with Ca, Mg, Na and K from the fresh rock up to the soil horizons, and ilmenite and xenotime were the main sources of Yb, Y, Co and P. The patterns of signatures and anomalies were different for light (LREEs), middle (MREEs) and heavy rare earth elements (HREEs) and for regoliths in different metamorphic complexes. The LREEs related well with the clay fraction amount, the poorly crystallized iron oxides and the degree of weathering, as estimated by the mineralogical index of alteration (MIA), while the HREEs related well with the total organic carbon (TOC). In particular, Ce was strongly associated with Mn oxides, possibly due to simultaneous oxidative precipitation.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 353〈/p〉 〈p〉Author(s): Marcel Lorenz, Sören Thiele-Bruhn〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉The purpose of this research was to evaluate tree species effects on quantitative and qualitative soil organic matter (SOM) properties of forest floors and mineral soil layers. Additionally, the contribution of soil microbial biomass to SOM was studied in five forest stands with different dominant tree species.〈/p〉 〈p〉The study was conducted at the afforested spoil heap ‘Sophienhöhe’ located at the lignite open-cast mine Hambach near Jülich, Germany. The 35 year-old afforested sites consisted of monocultural stands of Douglas fir (〈em〉Pseudotsuga mienziesii〈/em〉), pine (〈em〉Pinus nigra〈/em〉), beech (〈em〉Fagus sylvatica〈/em〉) and red oak (〈em〉Quercus rubra〈/em〉) as well as a mixed deciduous stand site planted mainly with hornbeam (〈em〉Carpinus betulus〈/em〉), lime (〈em〉Tilia cordata〈/em〉) and common oak (〈em〉Quercus robur〈/em〉). There, boundary conditions regarding soil, climate, topography and management were highly similar, equivalent to a common garden experiment but on landscape level. Because the parent material used for site recultivation was free from organic matter or coal material, the SOM accumulation is a result of in situ soil development.〈/p〉 〈p〉Tree species had a significant effect on soil organic carbon (SOC) stocks, stoichiometric patterns of C, hydrogen (H), nitrogen (N), oxygen (O) and sulfur (S) and the microbial biomass carbon (MBC) content in the forest floor and the top mineral soil layers (0–5 cm, 5–10 cm, 10–30 cm). In general, forest floor SOC stocks were significantly higher in coniferous forest stands compared to deciduous tree species. Differences in SOM quantity became less pronounced with increasing depth, while stoichiometric molar ratios of SOM as indices of litter turnover and SOM composition differed also in deeper layers. Differences in H:C and O:C ratios among tree species clearly increased along the depth gradient in mineral soils, indicating that SOM turnover by oxidative processes depends on tree species. Differences in depth gradients of the microbial quotient (MBC to SOC ratio) among tree species emphasized differences in the microbial C turnover. Furthermore, the relationship between the microbial quotient and SOM stoichiometry (C:N and C:S ratio) became stronger with increasing soil depth. This suggests that N and especially S limitation determined the microbial turnover of SOM in deeper mineral soil layers.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 348〈/p〉 〈p〉Author(s): Shi-Wei Li, Helian Li, Xuemei Han, Yibing Ma〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉After water-soluble nickel (Ni) is added to soils, its bioavailability/toxicity, isotopic exchangeability, and extractability decline over time. Two separate semi-mechanistic models (Sqrt-model and Ln-model), have been developed to predict short- and long-term aging of Ni added to soils. To continuously predict Ni aging in one model, a semi-mechanistic model (Erfc-model) was developed in the present study where the description of the diffusion process was based on a complementary error function. The Erfc-model for whole course aging predicted short- and long-term Ni aging continuously with regression coefficients (R〈sup〉2〈/sup〉) of 0.87 and 0.94, which were comparable with the Sqrt-model (0.91) and Ln-model (0.89). Based on the Erfc-model, soil pH and aging time were two important factors influencing the Ni aging processes. An additional 45 soils covering short and long terms of aging were applied to validate the model. A strong correlation (R〈sup〉2〈/sup〉 = 0.85) was found between the measured and the predicted lability of Ni in soils with root-mean-square-error (RMSE) of 8.97%, illustrating that the Erfc-model could continuously predict short- and long-term aging processes of Ni added to soils. The model could be used as an alternative to normalize ecotoxicological data for driving soil environmental quality standards.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 348〈/p〉 〈p〉Author(s): Yinping Chen, Jiangbao Xia, Ximei Zhao, Yuping Zhuge〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The construction of a shrub-grass community is the main action of vegetation restoration and ecological reconstruction on Shell Island, which is located in the Yellow River Delta, China. Three vegetation types—a mixed shrub-grass pattern, pure shrub, and pure grass—were studied, with bare land as the control, to elucidate the water retention characteristics of shell sand and the factors influencing the typical shrub and grass vegetation on Shell Island in the Yellow River Delta. Soil moisture physical parameters, such as the bulk density, particle size composition, particle fractal dimension and water storage capacity, were measured and analysed under different vegetation types, and the potential and main factors influencing the soil water retention were comprehensively evaluated. The results showed that (1) the bulk densities of the 0–40 cm layer of soil under the shrub-grassland, shrub land, and grassland were significantly lower and the total porosity was significantly higher than that under bare land. The coarse sand particle content in the shell sand was the highest (55.32%), followed by the fine sand particles and gravel contents. The silt-clay content was low (2.37%). The planting of mixed shrub-grass could reduce the gravel and coarse sand contents and increased the fine sand and silt-clay contents. (2) The ranking of the soil particle fractal dimension, capillary water retention, soil water retention, effective retention and rainfall retention of the different vegetation types was as follows: mixed shrub-grassland 〉 shrub land 〉 grassland 〉 bare land. In terms of the vertical structure, the soil water retention in the 0–20 cm soil layer was higher than that in the 20–40 cm layer under all vegetation types. (3) The improvements to the soil physical properties and water storage capacity under the three vegetation types on Shell Island, the mixed shrub-grassland was the best, followed by shrub land and then, grassland. Moreover, the improvement in the 0–20 cm layer of the shell sand was better than that in the 20–40 cm layer. The soil bulk density, coarse sand, fine sand, capillary porosity, void ratio and fractal dimension were closely related to the soil water retention capacity and can be used as indicators to evaluate the water storage capacity of shell sand.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 348〈/p〉 〈p〉Author(s): Bernard Fungo, Zhe Chen, Klaus Butterbach-Bahl, Johannes Lehmannn, Gustavo Saiz, Víctor Braojos, Allison Kolar, Tatjana F. Rittl, Moses Tenywa, Karsten Kalbitz, Henry Neufeldt, Michael Dannenmann〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Biochar has been reported to reduce emission of nitrous oxide (N〈sub〉2〈/sub〉O) from soils, but the mechanisms responsible remain fragmentary. For example, it is unclear how biochar effects on N〈sub〉2〈/sub〉O emissions are mediated through biochar effects on soil gross N turnover rates. Hence, we conducted an incubation study with three contrasting agricultural soils from Kenya (an Acrisol cultivated for 10-years (Acrisol10); an Acrisol cultivated for over 100-years (Acrisol100); a Ferralsol cultivated for over 100 years (Ferralsol)). The soils were amended with biochar at either 2% or 4% w/w. The 〈sup〉15〈/sup〉N pool dilution technique was used to quantify gross N mineralization and nitrification and microbial consumption of extractable N over a 20-day incubation period at 25 °C and 70% water holding capacity of the soil, accompanied by N〈sub〉2〈/sub〉O emissions measurements. Direct measurements of N〈sub〉2〈/sub〉 emissions were conducted using the helium gas flow soil core method. N〈sub〉2〈/sub〉O emissions varied across soils with higher emissions in Acrisols than in Ferralsols. Addition of 2% biochar reduced N〈sub〉2〈/sub〉O emissions in all soils by 53 to 78% with no significant further reduction induced by addition at 4%. Biochar effects on soil nitrate concentrations were highly variable across soils, ranging from a reduction, no effect and an increase. Biochar addition stimulated gross N mineralization in Acrisol-10 and Acrisol-100 soils at both addition rates with no effect observed for the Ferralsol. In contrast, gross nitrification was stimulated in only one soil but only at a 4% application rate. Also, biochar effects on increased NH〈sub〉4〈/sub〉〈sup〉+〈/sup〉 immobilization and NO〈sub〉3〈/sub〉〈sup〉−〈/sup〉consumption strongly varied across the three investigated soils. The variable and bidirectional biochar effects on gross N turnover in conjunction with the unambiguous and consistent reduction of N〈sub〉2〈/sub〉O emissions suggested that the inhibiting effect of biochar on soil N〈sub〉2〈/sub〉O emission seemed to be decoupled from gross microbial N turnover processes. With biochar application, N〈sub〉2〈/sub〉 emissions were about an order of magnitude higher for Acrisol-10 soils compared to Acrisol-100 and Ferralsol-100 soils. Our N〈sub〉2〈/sub〉O and N〈sub〉2〈/sub〉 flux data thus support an explanation of direct promotion of gross N〈sub〉2〈/sub〉O reduction by biochar rather than effects on soil extractable N dynamics. Effects of biochar on soil extractable N and gross N turnover, however, might be highly variable across different soils as found here for three typical agricultural soils of Kenya.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0016706119300850-ga1.jpg" width="301" alt="Unlabelled Image" title="Unlabelled Image"〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 348〈/p〉 〈p〉Author(s): Manyun Zhang, Jun Wang, Shahla Hosseini Bai, Yaling Zhang, Ying Teng, Zhihong Xu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉There are growing trends of combined contaminations in agricultural soils, and therefore it is urgently needed to remediate contaminated soils with eco-friendly approaches. This study aimed to evaluate the effects of 〈em〉Medicago sativa〈/em〉 L. (alfalfa) planting, alone or together with biochar additions, on contaminant removals and bacterial properties in an agricultural soil contaminated by heavy metal and organic fungicide. The treatments in this study included: the control (CK), alfalfa planting (AP), alfalfa planting +1.5% biochar addition (w/w) (AP + 1.5B), alfalfa planting +3.0% biochar addition (AP + 3.0B), and alfalfa planting +6.0% biochar addition (AP + 6.0B). Relative to the alfalfa planting only, extra biochar additions increased alfalfa biomass and heavy metal cadmium (Cd) phytoextraction. The alfalfa planting, alone or together with biochar additions, significantly decreased soil iprodione concentrations. After 90 days of remediation, bacterial 16S rRNA gene abundances of the AP, AP + 1.5B, AP + 3.0B and AP + 6.0B treatments were 1.69, 3.84, 3.34 and 3.13 times as great as that obtained from the CK treatment, respectively. The AP + 1.5B treatment had the highest richness estimators and Shannon diversity index, but the AP + 6.0B treatment had the lowest invsimpson diversity index among the five treatments. The relative abundances of 〈em〉Bacteroidetes〈/em〉 and 〈em〉Nitrospirae〈/em〉 were enhanced by the alfalfa phytoremediation, alone or together with biochar additions. Our results suggest that the alfalfa has promising potentials in the remediation of co-contaminated soil and in the increases of soil bacterial biomass and community diversity. Simultaneously, biochar is beneficial to enhance Cd phytoextraction, however, biochar addition rate would need to be optimized.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉The alfalfa, alone or together with the biochar addition, has promising potentials in the remediation of co-contaminated soil and in the increase of soil bacterial biomass. Biochar is beneficial to enhance phytoremediation performance, however, biochar addition rates would need to be optimized.〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0016706118318627-ga1.jpg" width="368" alt="Unlabelled Image" title="Unlabelled Image"〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 347〈/p〉 〈p〉Author(s): 〈/p〉

Description: 〈p〉Publication date: 15 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 348〈/p〉 〈p〉Author(s): H.E. Bowley, S.D. Young, E.L. Ander, N.M.J. Crout, M.J. Watts, E.H. Bailey〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Iodine is an essential trace element for humans and grazing animals and is often deficient. Our aim was to investigate the role of soil properties in retaining and ‘fixing' iodine in soils and thereby controlling its phyto-availability to grass. Soils were spiked with labelled 〈sup〉129〈/sup〉IO〈sub〉3〈/sub〉〈sup〉−〈/sup〉 and rye grass (〈em〉Lolium perenne〈/em〉 L.) was grown to measure iodine uptake by grass as a function of yield, soil properties and continuous 〈sup〉127〈/sup〉I inputs from irrigation water. Iodine-129 added at the start of the uptake trial was rapidly fixed (t〈sub〉1/2〈/sub〉 c. 40 h) into non-labile humus-bound forms in soil. The 〈sup〉129〈/sup〉I/〈sup〉127〈/sup〉I isotopic ratio in grass, compared to the ratio in soil, declined over time confirming progressive 〈sup〉129〈/sup〉I fixation into the soil solid phase. The rate of fixation was controlled by soil properties. A model describing iodine dynamics and uptake accounted for c. 75% of the variation in iodine concentration in grass. For most of the soils studied, the main source of iodine in herbage probably arises from the transient availability of periodic rainfall inputs rather than from soil sources. This is expected to improve biofortification strategies.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 348〈/p〉 〈p〉Author(s): Shangshi Liu, Haihua Shen, Xia Zhao, Luhong Zhou, He Li, Longchao Xu, Aijun Xing, Jingyun Fang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Forest soil is a large carbon (C) pool and plays a pivotal role in the global C cycle. The accurate estimation of soil organic carbon (SOC) stocks in forests is the cornerstone of studying the C budget; however, current assessments of forest SOC stocks are highly uncertain. One of the key reasons for this uncertainty is that most previous studies only used a few soil profiles for their estimation, whereas SOC stocks are highly spatially heterogeneous. To accurately evaluate the plot-level SOC stocks of China's forests, we conducted intensive soil sampling (100 soil cores within a plot) in 33 plots across 11 forest sites from south to north China. The average SOC density (SOCD) of these forest sites was 137.4 ± 12.1 Mg C ha〈sup〉−1〈/sup〉 (0–100 cm), with significant geographic variations. The highest SOCD (306.8 ± 7.6 Mg C ha〈sup〉−1〈/sup〉) was observed in deciduous needleleaf forest (boreal forest) in northeast China, while the lowest one (64.8 ± 0.9 Mg C ha〈sup〉−1〈/sup〉) was found in subtropical evergreen broadleaf forest in south China. We also showed that the error of the SOCD estimates obtained from the intensive soil sampling was significantly smaller than that of estimates obtained from the traditional sampling method (5.3 ± 1.3% vs. 24.2 ± 5.6%, with a confidence level of 0.95). Our results suggest that intensive sampling can significantly reduce the uncertainty in forest SOC stock estimation by guarding against the effects of spatial heterogeneity, and provide an important methodological reference for accurately evaluating forest SOC stocks and C budgets in other regions.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 348〈/p〉 〈p〉Author(s): Youjin Yan, Quanhou Dai, Xiangdong Wang, Li Jin, Lina Mei〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Vegetation restoration is one of the effective means to control soil erosion and an essential method of eco-environmental restoration in fragile karst rocky desertification areas. The shallow karst fissure (SKF) filled with soil has become one of the most important root habitats in this area. It is essential to scientifically evaluate the soil quality of SKF and to provide a basis for matching species with sites. Here, we explore and gain insight into the characteristics of the response of the physicochemical properties of SKF soil to different stages of vegetation succession. Additionally, we develop a synthetical assessment system to determine soil quality. The key results were as follows. Significant differences were found in the soil properties between the surface and the SKF. Compared with the surface, the SKF soil structural property was poor, but the water conditions were better. The soil nutrient content of the SKF was significantly (〈em〉p〈/em〉 〈 0.05) lower than that of the surface, but the differences in soil nutrients inside the SKF were not significant. In addition, the soil quality indicator (SQI) values of the SKF soil were significantly (〈em〉p〈/em〉 〈 0.05) lower than those of the surface and decreased gradually with soil depth. Moreover, secondary succession significantly (〈em〉p〈/em〉 〈 0.05) improved the soil properties and, thus, the soil quality. With recovery of vegetation, the soil properties of the surface and the SKF were significantly improved. The difference in the soil properties and the SQI values between the surface and underground gradually narrowed with succession. Furthermore, the thickness of the SKF soil was more than twice that of the surface soil. Overall, the soil properties and the soil quality of the SKF were relatively poor, but they were greatly improved with vegetation restoration. The SKF habitat can be the preferred habitat for vegetation restoration and is more favourable for plants with deep roots and a higher root penetration ability. The results of this study can supply references for future studies on karst rocky desertification control and vegetation restoration in the karst area of southwestern China, northern and central Vietnam, the islands of Java, Indonesia and Kampot Province, southwestern Cambodia and other karst regions with the same ecological background.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0016706119300357-ga1.jpg" width="500" alt="Unlabelled Image" title="Unlabelled Image"〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 348〈/p〉 〈p〉Author(s): Xiaoning Zhao, Hannah Conrads, Chengyi Zhao, Joachim Ingwersen, Karl Stahr, Xiaorong Wei〈/p〉 〈div xml:lang="en"〉 〈h5〉Absract〈/h5〉 〈div〉〈p〉Previous studies have observed a negative CO〈sub〉2〈/sub〉 efflux from semi-desert and desert soil, but the carbon uptake in alkaline soils has not been measured quantitatively in laboratory. The present study aims at closing this gap considering the effect of temperature, soil pH and pCO〈sub〉2〈/sub〉. CO〈sub〉2〈/sub〉 uptake was studied with the help of the Barometric Process Separation (BaPS) technique. CO〈sub〉2〈/sub〉 uptake was studied at 3 different temperatures viz. 15, 20 and 25 °C. CO〈sub〉2〈/sub〉 uptake was observed after CO〈sub〉2〈/sub〉 injection with pH values ranging from 8 to 10 in desert Solonchak soils. We found that CO〈sub〉2〈/sub〉 uptake depended on pCO〈sub〉2〈/sub〉 and temperature. CO〈sub〉2〈/sub〉 uptake occurred rapidly within the first 10 min after the CO〈sub〉2〈/sub〉 injection and gradually slowed down afterwards. Results showed that 72%–97% of injected CO〈sub〉2〈/sub〉 was taken up by soils (pH 8–10). CO〈sub〉2〈/sub〉 uptake increased as soil pH increased and its uptake reached equilibrium faster in soil with a lower pH level (pH 〈 9) than in soil with a higher pH level (pH ≥ 9). Dissolved CO〈sub〉2〈/sub〉 (CO〈sub〉2aq〈/sub〉) (μmol ml〈sup〉−1〈/sup〉) increased with increasing CO〈sub〉2〈/sub〉 partial pressure (pCO〈sub〉2〈/sub〉) with equation y = a (1-b〈sup〉x〈/sup〉) (r〈sup〉2〈/sup〉 〉 0.96) and pH. The lower temperature produced a higher CO〈sub〉2aq〈/sub〉 for the same pCO〈sub〉2〈/sub〉 value. In conclusion, desert soils can rapidly uptake of CO〈sub〉2〈/sub〉, and the main controlling process of CO〈sub〉2〈/sub〉 uptake in the desert soils was decided by soil pH and temperature. The CO〈sub〉2〈/sub〉 uptake by the soil solution may be an important pathway for C sequestration in semi-desert and desert regions.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 348〈/p〉 〈p〉Author(s): Jerzy Jonczak, Wacław Florek, Bogusława Kruczkowska, Joanna Gadziszewska, Monika Niska, Łukasz Uzarowicz〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The study aimed to reconstruct major phases of the litho-morpho-pedogenic processes in the southern Baltic coastal zone near Dębina in northern Poland. Five profiles of fossil soils in the coastal cliff were described, sampled and analysed using standard procedures. The studied outcrop covers a sequence of deposits, including the basal till of the Świecie Stadial (MIS 4) of the Vistula Glaciation, the ablation till of the Pomeranian Phase (MIS 2) of the Vistula Glaciation, the thin cover of glacilimnic sand, the lacustrine sediments filling the palaeolake basin, and aeolian deposits of varied age. A sequence of paleosols developed successively within these deposits during the Late Vistulian and Holocene (MIS 1). The initialization of soil-forming processes occurred under the influence of periglacial environment and pioneer tundra vegetation. Endostagnic Podzols (Abruptic, Epiarenic, Endoloamic, Endodensic) developed within the plateau, and they have some features typical for periglacial environments (e.g. the presence of a cryoilluvial horizon, the poor humification of soil organic matter, the low abundance in N and P, and the vertical displacement of P). The basin of a small lake has been filled successively with sediments and Dystric Endocalcaric Katostagnic Fluvisols (Arenic, Humic, Endolimnic) developed from these sediments during the Late Vistulian and Early Holocene. The previously mentioned soils were buried by sandy cover in the Early Subatlantic due to intensification of aeolian processes. Ortsteinic Podzols (Pantoarenic) developed within a newly formed sandy cover. A fossil fireplace preserved in the top of these soils constitutes evidence of human activity dating back almost 2000 years. Ortsteinic Podzol (Pantoarenic) are dissected by a dry valley that developed as a result of some fluvial episode, perhaps induced by human activity. It was subsequently filled with aeolian sands, and Dystric Arenosols (Aeolic, Ochric) developed within them. Ortsteinic Podzol (Pantoarenic) and Dystric Arenosols (Aeolic, Ochric) were buried approximately five centuries ago. Our findings for the studied cliff section correlate well with results of other authors concerning the postglacial dynamics of morphogenetic processes. The studies provide significantly enriched geomorphological knowledge related to the formation of relief in the study area, with pedological aspects.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 347〈/p〉 〈p〉Author(s): Chen Wang, Rong Xiao, Yuan Cui, Ziwen Ma, Yutong Guo, Qian Wang, Yujiao Xiu, Mingxiang Zhang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Photosynthetic carbon is an integral part of carbon cycle in plant-soil system, also is an important source of soil organic carbon. In this study, 〈sup〉13〈/sup〉C labeling was used for exploring allocation of photosynthate-〈sup〉13〈/sup〉C in 〈em〉Phragmites australis〈/em〉 -soil system undergoing the salt marsh restoration project by freshwater pumping in Yellow River Estuary (YRE), China. Samples were collected from T〈sub〉0〈/sub〉 (before labeling) to 90 days after labeling (T〈sub〉4〈/sub〉), in natural salt marsh, 5-, 10- and 15-year freshwater pumping areas, respectively. The photosynthate-〈sup〉13〈/sup〉C contents of soil were gradually decreased to 0 mg/g at T〈sub〉4〈/sub〉 in most areas, while it was 2.21 mg/g in 15-year pumping area, higher than other areas at the last sampling time (T〈sub〉4〈/sub〉). And the allocation of photosynthate-〈sup〉13〈/sup〉C in soil was increased from 3.58% at T〈sub〉2〈/sub〉 to 44.46% at T〈sub〉3〈/sub〉 in natural salt marsh, while no significant change was found in other areas from T〈sub〉2〈/sub〉 to T〈sub〉3〈/sub〉, followed by the significantly higher photosynthate-〈sup〉13〈/sup〉C proportion in soils of 15-year pumping area at T〈sub〉4〈/sub〉. EC (R〈sup〉2〈/sup〉 = 0.5972) and small macro-aggregates proportion of soil (R〈sup〉2〈/sup〉 = 0.4829) had positive correlations with Δ photosynthate-〈sup〉13〈/sup〉C (the value of photosynthate-〈sup〉13〈/sup〉C in underground part minus that in soil); silt and clay fractions proportion of soil (R〈sup〉2〈/sup〉 = 0.7044) had negative correlation with Δ photosynthate-〈sup〉13〈/sup〉C. Distribution and transportation of photosynthetic carbon in the underground were affected by soil physical and chemical properties.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 347〈/p〉 〈p〉Author(s): E. Van Ranst, F. Mees, E. De Grave, L. Ye, J.-T. Cornelis, B. Delvaux〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The accumulation of soil organic matter (SOM), poorly crystalline Fe oxides and metal-humus complexes is a trait of non-allophanic Andosols. The process of andosolization, which may occur in ferrallitic soils with high organic matter content, can involve transformation from well crystallized Fe oxides to poorly crystallized Fe oxides and Fe-humus complexes. This study investigates such changes in pedogenic Fe mineral associations for a soil toposequence between 1500 and 2260 m altitude along the southern flank of the volcanic Bambouto Mountains, Western Cameroon. The soils consist of highly weathered material, dominated by kaolinite, gibbsite and Fe oxides, grading to Protoandic Umbrisols at high altitude, recording an increase in SOM content with increasing altitude. As revealed by selective extraction analysis, the relative amount of poorly crystalline Fe oxides is low in the Bt and Bo horizons of low-altitude pedons, as well as in deep subsurface horizons of the high-altitude pedons. In contrast, it is significantly higher in the A and Bw horizons of the high-altitude pedons, with a clear increase with increasing altitude. Mössbauer spectroscopy analysis of B horizon samples identifies goethite as the dominant Fe oxide phase in nearly all pedons, with higher hematite contents in a mid-altitude zone marked by lower annual rainfall than in other parts of the toposequence. The Mössbauer spectra also reveal the presence of dissolved organic matter (DOM)-ferrihydrite, whose abundance is greatest in the Bw horizon of the high-altitude pedons, with an increase in relative abundance with increasing altitude. The observed patterns are attributed to dissolution-reprecipitation of Fe oxides that initially formed through ferrallitic weathering of volcanic parent materials that were roughly uniform along the toposequence. At high altitude, coupled hematite dissolution and DOM-ferrihydrite formation are favoured by high organic matter contents and low pH, related to cool humid environmental conditions and their effect on the vegetation and organic matter cycling.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 June 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 343〈/p〉 〈p〉Author(s): Vaibhav Chhipa, Alfred Stein, Hari Shankar, Justin George K, Fakhereh Alidoost〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Spatial variability of soil health related variables in a hilly terrain may be high, and its characterization may require many samples. Our research compares deterministic and geostatistical interpolation methods in two hilly areas in India. The soil in the study area was acidic, without salts and with sufficient organic carbon content. Hence, three soil parameters – pH, Electrical Conductivity (EC) and Total Organic Carbon (TOC) were considered. The optimal sampling scheme was designed using Spatial Simulated Annealing (SSA) with the minimized kriging variance as a criterion. This resulted in 96 locations in the first area and 7 locations in the second area. It was explored how spatial information from one area could be used in a second, topographically similar area. The study focused on pH as the key variable for soil health. Regression kriging performed best for all the soil variables at the surface and sub-surface levels. Bayesian kriging allows one to use prior information and hence was used to transfer from the first to the second area. A mean error of 0.15, a root mean square error of 0.28 and a residual variance equal to 0.73 respectively were observed. We conclude that with modern interpolation methods important information on soil health can be collected even with sparse amounts of data.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 348〈/p〉 〈p〉Author(s): David Peña, Ángel Albarrán, Soraya Gómez, Damián Fernández-Rodríguez, José Manuel Rato-Nunes, Antonio López-Piñeiro〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Laboratory and field experiments were conducted on three Mediterranean agricultural soils in so as to investigate the effects of de-oiled two-phase olive mill waste (D) and two-phase olive mill waste (W) and their level of organic matter maturity on the environmental fate of the herbicide S‑metolachlor (SM). Three Mediterranean agricultural soils were amended with fresh (D and W) and composted W (CW) wastes under laboratory conditions. Furthermore, under field conditions, one of the soils was also amended with both wastes (D and W) over 9 years in order to assess the effects of the “aging” transformation (AD and AW treatments, respectively). Significant increases in SM adsorption were observed in all the amended soils, with no reduction in the herbicide's effectiveness. The adsorption process was more reversible with the fresh organic amendments (D or W) than with CW or (even more so) with AD or AW. The fresh amendments also increased the persistence of SM; however the field-aged and composted amendments enhanced its dissipation as a result increased soil microbial activity showed by high levels of soil dehydrogenase activity. The AD- and AW-amended soils, showed the greatest decrease in leaching loss of SM (from 51.9% in original soil to 9.33% in AD and 8.05% in AW), reflecting the strong influence of adsorption-desorption processes on SM leaching. This study has shown that the application of olive mill wastes as organic amendments may be considered a useful strategy to reduce leaching of SM in soils poor in organic matter, especially if those wastes have a high level of organic matter maturity.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0016706118320998-ga1.jpg" width="301" alt="Unlabelled Image" title="Unlabelled Image"〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 348〈/p〉 〈p〉Author(s): Qun Liu, Liyan Zhuang, Rui Yin, Xiangyin Ni, Chengming You, Kai Yue, Bo Tan, Yang Liu, Li Zhang, Zhenfeng Xu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The humification of plant litter is a crucial step for the buildup of soil organic matter in terrestrial ecosystems. Yet, how environmental change and substrate quality affect root humification still remains poorly understood. A two-year litterbag experiment was conducted to assess the root mass remaining and accumulation of humic substances in roots of three diameter classes (0–2, 2–5 and 5–10 mm) of two common subalpine tree species (〈em〉Picea asperata〈/em〉 and 〈em〉Abies faxoniana〈/em〉) at two elevations (3037 m and 3580 m) on the eastern Tibetan Plateau. No significant differences were found between elevation treatments in the concentration of humic substances. Both root mass loss and concentrations of humic substance, humic acid and fulvic acid decreased with increasing root diameter. Both fulvic acid concentration and humification degree declined as root decomposition progressed but humic acid concentration exhibited an opposite trend. Our results reveal that the diameter-associated variations in accumulation of humic substances were substantially stronger than altitudinal and interspecific differences in decomposing root litters. These findings have important implications for carbon sequestration via root humification in the subalpine forests experiencing snow-covered winter.〈/p〉〈/div〉 〈/div〉