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  • 1
    Electronic Resource
    Electronic Resource
    The effects of live and dead roots on soil fungi in spodosolic soils of the New Jersey Pinelands (1996)
    Springer
    Biology and fertility of soils 21 (1996), S. 215-226 
    Details
    ISSN: 1432-0789
    Keywords: Dead roots ; Fluorescein diacetate-active hyphae ; Field mesocosms ; Live roots ; Mor humus ; Mycorrhizae ; New Jersey Pinelands ; Spodosolic forest soils
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The effects of live and dead roots on soil fungi were investigated experimentally in a spodosolic soil of the New Jersey Pinelands. Field mesocosm plots were constructed to have a layer of either C- and N-rich organic soil or a vermiculite substitute overlying a layer of sandy mineral soil with a very low organic content. The plots were also supplied with live pitch pine and blueberry roots or dead pitch pine roots in varying quantities based on anturally occurring densities (half, same, and double the ambient quantities). All plots were sampled 1 year after construction (June 1991), and three more times in two subsequent years (November 1991, June 1992, June 1993). In the presence of live roots, fluorescein diacetate-determined (FDA-active) fungal hyphae, total fungal hyphae, and soil moisture decreased significantly in the organic material, while no change was associated with the dead roots. The FDA-active fungal length in the live-root plots ranged from 40 to 165 mg-1 soil, and from 55 to 335 mg-1 soil in the dead-root plots. While the total fungal length in live-root plots remained constant over time (∼3000 mg-1 soil), the total fungal length in the dead-root plots increased from an initial value of 3000 to 〉4000 mg-1 soil at the conclusion of the study. Fungal lengths in mineral soil were higher under organic material than under the vermiculite substitute. Soil moisture was higher in the presence of live roots in mineral soils, but this did not increase the fungal abundance. Inputs of dead roots did not alter the fungal abundance. Overall, we demonstrated that live and dead roots had different effects on fungal abundance in soils with contrasting qualities, and in a spodosolic forest soil, roots could have ecosystem effects very different from those in agricultural soils.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00335938
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    The effects of mycorrhizal roots on litter decomposition, soil biota, and nutrients in a spodosolic soil (1996)
    Springer
    Plant and soil 179 (1996), S. 109-118 
    Details
    ISSN: 1573-5036
    Keywords: decomposition ; mycorrhizal roots ; nematodes ; soil microbial biomass ; soil nutrients ; spodosolic soil
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract We studied the effects of mycorrhizal pitch pine (Pinus rigida) roots on litter decomposition, microbial biomass, nematode abundance and inorganic nutrients in the E horizon material of a spodosolic soil, using field microcosms created in a regenerating pitch pine stand in the New Jersey Pinelands. Pine roots stimulated litter decomposition by 18.7% by the end of the 29 month study. Both mass loss and N and P release from the litter were always higher in the presence of roots than in their absence. Nutrient concentrations in decomposing litter were similar, however, in the presence and absence of roots, which suggests that the roots present in the with-root treatment did not withdraw nutrients directly from the litter. The soil was slightly drier in the presence of roots, but there was no discernible effect on soil microbial biomass. The effects of roots on soil extractable inorganic nutrients were inconsistent. Roots, however, were consistently associated with higher numbers of soil nematodes. These results suggest that, in soils with low total C and N contents, roots stimulate greater activity of the soil biota, which contribute, in turn, to faster litter decomposition and nutrient release.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00011648
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  • 3
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    Microbial denitrification dominates nitrate losses from forest ecosystems (2015)
    National Academy of Sciences
    Details
    Publication Date: 2015-01-20
    Description: Denitrification removes fixed nitrogen (N) from the biosphere, thereby restricting the availability of this key limiting nutrient for terrestrial plant productivity. This microbially driven process has been exceedingly difficult to measure, however, given the large background of nitrogen gas (N2) in the atmosphere and vexing scaling issues associated with heterogeneous soil systems. Here, we use natural abundance of N and oxygen isotopes in nitrate (NO3−) to examine dentrification rates across six forest sites in southern China and central Japan, which span temperate to tropical climates, as well as various stand ages and N deposition regimes. Our multiple stable isotope approach across soil to watershed scales shows that traditional techniques underestimate terrestrial denitrification fluxes by up to 98%, with annual losses of 5.6–30.1 kg of N per hectare via this gaseous pathway. These N export fluxes are up to sixfold higher than NO3− leaching, pointing to widespread dominance of denitrification in removing NO3− from forest ecosystems across a range of conditions. Further, we report that the loss of NO3− to denitrification decreased in comparison to leaching pathways in sites with the highest rates of anthropogenic N deposition.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 4
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    Urban Wetland Characterization in South-Central New York State (2016)
    Springer
    Details
    Publication Date: 2016-06-29
    Print ISSN: 0277-5212
    Electronic ISSN: 1943-6246
    Topics: Biology
    Published by Springer
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  • 5
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    Remote Sensing, Vol. 7, Pages 5203-5221: Exploring the Vertical Distribution of Structural Parameters and Light Radiation in Rice Canopies by the Coupling Model and Remote Sensing (2015)
    MDPI Publishing
    Details
    Publication Date: 2015-04-25
    Description: Canopy structural parameters and light radiation are important for evaluating the light use efficiency and grain yield of crops. Their spatial variation within canopies and temporal variation over growth stages could be simulated using dynamic models with strong application and predictability. Based on an optimized canopy structure vertical distribution model and the Beer-Lambert law combined with hyperspectral remote sensing (RS) technology, we established a new dynamic model for simulating leaf area index (LAI), leaf angle (LA) distribution and light radiation at different vertical heights and growth stages. The model was validated by measuring LAI, LA and light radiation in different leaf layers at different growth stages of two different types of rice (Oryza sativa L.), i.e., japonica (Wuxiangjing14) and indica (Shanyou63). The results show that the simulated values were in good agreement with the observed values, with an average RRMSE (relative root mean squared error) between simulated and observed LAI and LA values of 14.75% and 21.78%, respectively. The RRMSE values for simulated photosynthetic active radiation (PAR) transmittance and interception rates were 14.25% and 9.22% for Wuxiangjing14 and 15.71% and 4.40% for Shanyou63, respectively. In addition, the corresponding RRMSE values for red (R), green (G) and blue (B) radiation transmittance and interception rates were 16.34%, 15.96% and 15.36% for Wuxiangjing14 and 5.75%, 8.23% and 5.03% for Shanyou63, respectively. The results indicate that the model performed well for different rice cultivars and under different cultivation conditions.
    Electronic ISSN: 2072-4292
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by MDPI Publishing
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  • 6
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    Remote Sensing, Vol. 11, Pages 1809: Estimating Leaf Area Index with a New Vegetation Index Considering the Influence of Rice Panicles (2019)
    MDPI
    Details
    Publication Date: 2019
    Description: The emergence of rice panicle substantially changes the spectral reflectance of rice canopy and, as a result, decreases the accuracy of leaf area index (LAI) that was derived from vegetation indices (VIs). From a four-year field experiment with using rice varieties, nitrogen (N) rates, and planting densities, the spectral reflectance characteristics of panicles and the changes in canopy reflectance after panicle removal were investigated. A rice “panicle line”—graphical relationship between red-edge and near-infrared bands was constructed by using the near-infrared and red-edge spectral reflectance of rice panicles. Subsequently, a panicle-adjusted renormalized difference vegetation index (PRDVI) that was based on the “panicle line” and the renormalized difference vegetation index (RDVI) was developed to reduce the effects of rice panicles and background. The results showed that the effects of rice panicles on canopy reflectance were concentrated in the visible region and the near-infrared region. The red band (670 nm) was the most affected by panicles, while the red-edge bands (720–740 nm) were less affected. In addition, a combination of near-infrared and red-edge bands was for the one that best predicted LAI, and the difference vegetation index (DI) (976, 733) performed the best, although it had relatively low estimation accuracy (R2 = 0.60, RMSE = 1.41 m2/m2). From these findings, correcting the near-infrared band in the RDVI by the panicle adjustment factor (θ) developed the PRDVI, which was obtained while using the “panicle line”, and the less-affected red-edge band replaced the red band. Verification data from an unmanned aerial vehicle (UAV) showed that the PRDVI could minimize the panicle and background influence and was more sensitive to LAI (R2 = 0.77; RMSE = 1.01 m2/m2) than other VIs during the post-heading stage. Moreover, of all the assessed VIs, the PRDVI yielded the highest R2 (0.71) over the entire growth period, with an RMSE of 1.31 (m2/m2). These results suggest that the PRDVI is an efficient and suitable LAI estimation index.
    Electronic ISSN: 2072-4292
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by MDPI
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  • 7
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    East-west differences in F-region electron density at midlatitude: Evidence from the Far East region (2013)
    Wiley
    Details
    Publication Date: 2013-02-01
    Description: [1]  The global configuration of the geomagnetic field shows that the maximum east-west difference in geomagnetic declination of northern middle latitude lies in the US region (~32°), which produces the significant ionospheric east-west coast difference in terms of total electron content first revealed by Zhang et al. (2011). For verification, it is valuable to investigate this feature over the Far East area, which also shows significant geomagnetic declination east-west gradient but smaller (~15°) than that of the US. The current study provides evidence of the longitudinal change supporting the thermospheric zonal wind mechanism by examining the climatology of peak electron density (NmF2), electron density (Ne) of different altitudes in the Far East regions with a longitude separation of up to 40–60° based on ground ionosonde and space-based measurements. Although the east-west difference ( R ew ) over the Far East area displays a clear diurnal variation similar to the US feature, that is negative R ew (West Ne 〉 East Ne) in the noon and positive at evening-night, the observational results reveal more differences including: (1) The noontime negative R ew is most pronounced in April–June while in the US during February–March. Thus, for the late spring and summer period negative R ew over the Far East region is more significant than that of the US. (2) The positive R ew at night is much less evident than in the US, especially without winter enhancement. (3) The magnitude of negative R ew tends to enhance toward solar maximum while in the US showing anticorrelation with the solar activity. The altitude distribution of pronounced negative difference (300–400 km) moves upward as the solar flux increases and hence produces the different solar activity dependence at different altitude. The result in the paper is not simply a comparison corresponding to the US results but raises some new features that are worth further studying and improve our current understanding of ionospheric longitude difference at midlatitude.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 8
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    Remote Sensing, Vol. 8, Pages 116: Preface: Recent Advances in Remote Sensing for Crop Growth Monitoring (2016)
    MDPI Publishing
    Details
    Publication Date: 2016-02-05
    Description: This Special Issue gathers sixteen papers focusing on applying various remote sensing techniques to crop growth monitoring. The studies span observations from multiple scales, a combination of model simulations and experimental measurements, and a range of topics on crop monitoring and mapping. This preface provides a brief overview of the contributed papers.
    Electronic ISSN: 2072-4292
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by MDPI Publishing
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  • 9
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    Remote Sensing, Vol. 11, Pages 1763: Combining Color Indices and Textures of UAV-Based Digital Imagery for Rice LAI Estimation (2019)
    MDPI
    Details
    Publication Date: 2019
    Description: Leaf area index (LAI) is a fundamental indicator of plant growth status in agronomic and environmental studies. Due to rapid advances in unmanned aerial vehicle (UAV) and sensor technologies, UAV-based remote sensing is emerging as a promising solution for monitoring crop LAI with great flexibility and applicability. This study aimed to determine the feasibility of combining color and texture information derived from UAV-based digital images for estimating LAI of rice (Oryza sativa L.). Rice field trials were conducted at two sites using different nitrogen application rates, varieties, and transplanting methods during 2016 to 2017. Digital images were collected using a consumer-grade UAV after sampling at key growth stages of tillering, stem elongation, panicle initiation and booting. Vegetation color indices (CIs) and grey level co-occurrence matrix-based textures were extracted from mosaicked UAV ortho-images for each plot. As a solution of using indices composed by two different textures, normalized difference texture indices (NDTIs) were calculated by two randomly selected textures. The relationships between rice LAIs and each calculated index were then compared using simple linear regression. Multivariate regression models with different input sets were further used to test the potential of combining CIs with various textures for rice LAI estimation. The results revealed that the visible atmospherically resistant index (VARI) based on three visible bands and the NDTI based on the mean textures derived from the red and green bands were the best for LAI retrieval in the CI and NDTI groups, respectively. Independent accuracy assessment showed that random forest (RF) exhibited the best predictive performance when combining CI and texture inputs (R2 = 0.84, RMSE = 0.87, MAE = 0.69). This study introduces a promising solution of combining color indices and textures from UAV-based digital imagery for rice LAI estimation. Future studies are needed on finding the best operation mode, suitable ground resolution, and optimal predictive methods for practical applications.
    Electronic ISSN: 2072-4292
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by MDPI
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  • 10
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    Remote Sensing, Vol. 11, Pages 1422: Generating Red-Edge Images at 3 M Spatial Resolution by Fusing Sentinel-2 and Planet Satellite Products (2019)
    MDPI
    Details
    Publication Date: 2019
    Description: High-resolution satellite images can be used to some extent to mitigate the mixed-pixel problem caused by the lack of intensive production, farmland fragmentation, and the uneven growth of field crops in developing countries. Specifically, red-edge (RE) satellite images can be used in this context to reduce the influence of soil background at early stages as well as saturation due to crop leaf area index (LAI) at later stages. However, the availability of high-resolution RE satellite image products for research and application globally remains limited. This study uses the weight-and-unmixing algorithm as well as the SUPer-REsolution for multi-spectral Multi-resolution Estimation (Wu-SupReME) approach to combine the advantages of Sentinel-2 spectral and Planet spatial resolution and generate a high-resolution RE product. The resultant fused image is highly correlated (R2 〉 0.98) with Sentinel-2 image and clearly illustrates the persistent advantages of such products. This fused image was significantly more accurate than the originals when used to predict heterogeneous wheat LAI and therefore clearly illustrated the persistence of Sentinel-2 spectral and Planet spatial advantage, which indirectly proved that the fusion methodology of generating high-resolution red-edge products from Planet and Sentinel-2 images is possible. This study provided method reference for multi-source data fusion and image product for accurate parameter inversion in quantitative remote sensing of vegetation.
    Electronic ISSN: 2072-4292
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by MDPI
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