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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    European journal of soil science 51 (2000), S. 0 
    ISSN: 1365-2389
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: We investigated the functional role of enchytraeid worms (Oligochaeta) in organic upland soils experimentally, because that role of these animals is little known. We made microcosms of intact soil cores cut from two depths, 0–4 cm and 4–8 cm, of a Cambic Stagnohumic Gley from the Moor House National Nature Reserve (UK). Enchytraeids were added to half of the microcosms, resulting in four treatments: litter (L), litter + enchytraeids (L + E), soil (S) and soil + enchytraeids (S + E). Triplicates of each treatment were established, and all microcosms (60) were then incubated in the dark at 15°C, arranged in a fully randomized design. The experiment ran over 110 days, with five destructive harvests at days 10, 25, 50, 75 and 110, when microbial measurements (soil respiration and biomass C) as well as measures of decomposition (nutrient concentration in leachates) were made. Enchytraeids almost doubled the availability of organic carbon (measured as dissolved organic carbon in soil leachates) in the surface (0–4 cm) microcosms only. There were no effects of enchytraeids on the release of inorganic N or P from either soil horizon, although the release of ammonium and phosphate was correlated with the number of enchytraeids in the microcosms. The depth from which the soil was taken exerted a strong influence on nutrient leaching, with almost six times more ammonium and four times more carbon being leached from the surface (0–4 cm) layer than from the more decomposed (4–8 cm) horizon. There was little nitrate leaching from any of the treatments, with only one-quarter as much nitrate leached from the surface (0–4 cm) as from the subsurface (4–8 cm) horizon. Enchytraeids had no detectable effect on microbial biomass, but they increased microbial respiration by 35% in the surface (0–4 cm) horizon. Because they enhanced microbial activity in this horizon we suggest that enchytraeids indirectly drive the processes of decomposition and nutrient mineralization in organic upland soils.
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  • 2
    ISSN: 1365-2389
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: We have sought to understand the molecular mechanisms by which dissolved organic matter (DOM) forms and soil organic matter (SOM) degrades in upland peaty gley soil under grass. Pyrolysis mass spectrometry (Py-MS) and pyrolysis gas chromatography mass spectrometry (Py-GC/MS) were applied to characterize the DOM collected from lysimeters and its parent SOM. The macromolecular organic matter in the litter and fermentation (Lf) horizon of the soil consists primarily of little decomposed lignocellulose from grass, whereas the humus (Oh) horizon is characterized by an accumulation of selectively decomposed lignocellulose material, microbial metabolites and bound fatty acids. The mineral horizon produced a relative enrichment of furan structures derived from microbial reworking of plant polysaccharides but virtually no lignin signals. A series of exceptional long chain C43 to C53 fatty acids with odd over even predominance, probably derived from mycobacteria, were also identified in the Oh horizon. Side-chain oxidation and shortening, increase of carboxyl functionality and selective removal of syringyl (S) 〉 guaiacyl (G) 〉 p-hydroxyphenyl (P) lignin units were the main reactions when lignin degraded. Compared with SOM, the DOM shows a large accumulation of more oxidized lignin and aromatic structures, especially those containing carboxylic and dicarboxylic acid functionalities and with shorter side-chain length. The polysaccharide-type compounds in the DOM were more modified (greater abundance of furan structures in pyrolysis products), and had significantly lower molecular weight and more diverse polymeric structures than did those in soils. Increased temperature and rainfall appeared to result in greater relative abundance of lignin degradation products and aromatic compounds in DOM.
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    European journal of soil science 47 (1996), S. 0 
    ISSN: 1365-2389
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: A combination of radiocarbon (14C) dating and biomarker analyses of the aliphatic hydrocarbons in soil lipids is proposed as a novel and improved method for studying the environmental history of peaty soils. The radiocarbon concentration of unfractionated bulk organic matter, hydrolysed soil residues and two lipid fractions (the aliphatic hydrocarbons and carboxylic acids) recovered from a stagnohumic gley soil, were compared using AMS (accelerator mass spectrometry) and radiometric 14C dating techniques. The radiocarbon ages recorded by the aliphatic hydrocarbon fractions were consistently older than those measured from the unfractionated soil, and were in most cases older than the residues remaining after acid hydrolysis. This pattern was observed at three different depths in the soil profile. The apparent age difference between the hydrocarbon fraction and its unfractionated substrate increased with depth. An abundance of long–chain n–alkanes, similar to those found in higher plant waxes, characterized the aliphatic hydrocarbon fraction from the deepest soil (at 21.5–24.5–cm depth). The radiocarbon age of this basal organic component (13470± 170 years bp) indicated that it derived from the initial re–establishment of vegetation on the local deglaciated landscape with the onset of the Windermere Interstadial (c. 14000–13000 14C years bp). Bulk organic detritus within the basal horizon dated at some 3000 years younger, and presumably as a result of the downward penetration and retention of some mobile organic residues produced later in the development of the soil profile. The survival and apparent stratigraphical stability of these recoverable aliphatic hydrocarbons provides the opportunity, via the development of AMS dating, to measure an unambiguous radiocarbon age for the origin of organic residues retained in soils and sediments.
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  • 4
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Sycamore (Acer pseudoplatanus L.) leaf litters from 15 woodlands exposed to a broad range of ambient sulphur dioxide (SO2) concentrations were fumigated with environmentally realistic concentrations (ll-20nmol mol−1) of SO2, for 166 d in an open-air fumigation experiment. Fumigation of the sycamore litters significantly increased sulphate-S and proton leaching, and decreased calcium, magnesium and potassium concentrations in leachates and leaf tissues. Leaf litters from relatively unpolluted woodlands showed a tendency to lose higher amounts of sulphate-S, calcium, magnesium and nitrate-N in leachates than litters from polluted sites when exposed to elevated levels of SO2 in treatment plots.Fumigation inhibited the decomposition rates (CO2 evolution) of the leaf litters. Marked changes in the composition of the saprotrophic fungal communities in SO2-fumigated leaf litters were also recorded, but fungal communities and responses to SO2, were similar between woodlands. There was no evidence from our data to suggest that resistance to SO2, was developed in decomposer mycofloras in woodlands more frequently polluted by the gas.
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  • 5
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Soil Biology and Biochemistry 25 (1993), S. 1513-1525 
    ISSN: 0038-0717
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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  • 6
    ISSN: 1432-1939
    Keywords: Key words Root birth ; Root death ; Minirhizotron ; Soil temperature ; PAR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Root demographic processes (birth and death) were measured using minirhizotrons in the soil warming experiments at the summit of Great Dun Fell, United Kingdom (845 m). The soil warming treatment raised soil temperature at 2 cm depth by nearly 3°C. The first experiment ran for 6 months (1994), the second for 18 (1995–1996). In both experiments, heating increased death rates for roots, but birth rates were not significantly increased in the first experiment. The lack of stimulation of death rate in 1996 is probably an artefact, caused by completion of measurements in late summer of 1996, before the seasonal demography was concluded: root death continued over the winter of 1995–1996. Measurements of instantaneous death rates confirmed this: they were accelerated by warming in the second experiment. In the one complete year (1995–1996) in which measurements were taken, net root numbers by the end of the year were not affected by soil warming. The best explanatory environmental variable for root birth rate in both experiments was photosynthetically active radiation (PAR) flux, averaged over the previous 5 (first experiment) or 10 days (second experiment). In the second experiment, the relationship between birth rate and PAR flux was steeper and stronger in heated than in unheated plots. Death rate was best explained by vegetation temperature. These results provide further evidence that root production acclimates to temperature and is driven by the availability of photosynthate. The stimulation of root growth due to soil warming was almost certainly the result of changes in nutrient availability following enhanced decomposition.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Oecologia 106 (1996), S. 525-530 
    ISSN: 1432-1939
    Keywords: Elevated CO2 ; N fertilization ; Decomposition ; Lignin/N ; Betula pendula
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effect of elevated atmospheric CO2 and nutrient supply on elemental composition and decomposition rates of tree leaf litter was studied using litters derived from birch (Betula pendula Roth.) plants grown under two levels of atmospheric CO2 (ambient and ambient +250 ppm) and two nutrient regimes in solar domes. CO2 and nutrient treatments affected the chemical composition of leaves, both independently and interactively. The elevated CO2 and unfertilized soil regime significantly enhanced lignin/N and C/N ratios of birch leaves. Decomposition was studied using field litter-bags, and marked differences were observed in the decomposition rates of litters derived from the two treatments, with the highest weight remaining being associated with litter derived from the enhanced CO2 and unfertilized regime. Highly significant correlations were shown between birch litter decomposition rates and lignin/N and C/N ratios. It can be concluded, from this study, that at levels of atmospheric CO2 predicted for the middle of the next century a deterioration of litter quality will result in decreased decomposition rates, leading to reduction of nutrient mineralization and increased C storage in forest ecosystems. However, such conclusions are difficult to generalize, since tree responses to elevated CO2 depend on soil nutritional status.
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  • 8
    ISSN: 1573-515X
    Keywords: transplanted soils ; ion budgets ; soil solution chemistry ; mineralization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Forest ecosystems are currently beingexposed to changes in chemical inputs and it issuggested that physical climate is also changing. Anovel approach has been used to study the effects ofionic inputs and climatic conditions on forest soilsby reciprocally exchanging lysimeters containingundisturbed soil columns beween four forest sites inEurope. The soil columns contained no living roots andsimulated a clear cut situation. The soils chosenrepresented different stages of acidification and weretaken from sites along a transect of increasingexposure to acidic and nitrogen pollution. The purposeof the study was to quantify the reactions of soilswhen transferred to different environments. Elementbalances were used as an aggregated indicator todescribe the reaction of the soil. The input of protonsin local throughfall increased along the transect from0.01 kmol ha-1 y-1H+ at the unpolluted site up to 1.10 kmolha-1 y-1 at the most pollutedsite. Our results show that soil acidification always resultedfrom a combination of acid deposition and biologicaltransformations of nitrogen through nitrification ofimported ammonium, mineralized N, or stored N. Thebalances indicate that between 54% and 91%of the soil acidification resulted from nitrificationprocesses which were driven by a complex reaction whenclimatic and pollution conditions were changedsimultaneously. The combined changes in atmosphicinputs and climatic conditions, as expected withglobal change, may have serious consequences for soilacidfication and long term organic matter turnover.
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  • 9
    ISSN: 1573-515X
    Keywords: acidification ; aluminium ; Arrhenius’ law ; calcium ; cation leaching ; climate ; ion equilibrium ; forest soil ; N-cycle ; N-deposition ; nitrification ; temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Increased emissions of nitrogen compounds have led to atmosphericdeposition to forest soils exceeding critical loads of N overlarge parts of Europe. To determine whether the chemistry offorest soils responds to changes in throughfall chemistry, intactsoil columns were reciprocally transplanted between sites, withdifferent physical conditions, across a gradient of N and Sdeposition in Europe. The transfer of a single soil to the various sites affected itsnet nitrification. This was not simply due to the nitrificationof different levels of N deposition but was explained bydifferences in physical climates which influenced mineralizationrates. Variation in the amount of net nitrification between soiltypes at a specific site were explained largely by soil pH. Within a site all soil types showed similar trends in netnitrification over time. Seasonal changes in net nitrificationcorresponds to oscillations in temperature but variable time lagshad to be introduced to explain the relationships. WithArrhenius‘ law it was possible to approximate gross nitrificationas a function of temperature. Gross nitrification equalled netnitrification after adaptation of the microbial community oftransplanted soils to the new conditions. Time lags, andunderestimates of gross nitrification in autumn, were assumed tobe the result of increased NH 4 + availability due either tochanges in the relative rates of gross and net N transformationsor to altered soil fauna-microbial interactions combined withimproved moisture conditions. Losses of NO 3 - were associated with Ca2+and Mg2+ in non-acidified soil types and with losses ofAl3+ in the acidified soils. For single soils the ionequilibrium equation of Gaines-Thomas provided a useful approximationof Al3+ concentrations in the soil solution as a functionof the concentration of Ca2+. The between site deviationsfrom this predicted equilibrium, which existed for single soils, couldbe explained by differences in throughfall chemistry which affectedthe total ionic strength of the soil solution. The approach of reciprocally transferring soil columnshighlighted the importance of throughfall chemistry, interactingwith the effect of changes in physical climate on forest soilacidification through internal proton production, in determiningsoil solution chemistry. A framework outlining the etiology offorest die-back induced by nitrogen saturation is proposed.
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  • 10
    ISSN: 1573-515X
    Keywords: aluminium ; forest soils ; lysimeters ; nitrification ; nitrogen ; roots
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The effects of enhanced (NH4 2SO4deposition on soil solution cation and anion concentrations and annualionic fluxes were followed using a standardised experimental protocolin six European coniferous forests with contrasting soil types, pollutioninputs and climate. Native soil cores containing a ceramic suction cupwere installed in the field, roofed and watered every two weeks withlocal throughfall or local throughfall with added(NH4)2SO4 at 75 kgNH4 +-N ha-1 a-1. Livingroot systems were established in half of the lysimeters.Untreated throughfall NH4 +-N deposition at thesites ranged from 3.7 to 29 kg ha-1 a-1Soil leachates were collected at two weekly intervalsover 12 months and analysed for volume, andconcentrations of major anions and cations. Increasesin soil solution NO3 - concentrations inresponse to N additions were observed after 4–9months at three sites, whilst one sandy soil with highC:N ratio failed to nitrify under any of thetreatments. Changes in NO3 - concentrationsin soil solution controlled soil solution cationconcentrations in the five nitrifying soils, withAl3+ being the dominant cation in the more acidsoils with low base saturation. The acidification responses ofthe soils to the (NH4 2SO4additions were primarily related to the ability of thesoils to nitrify the added NH4 +. pH and soiltexture seemed important in controllingNH4 + leaching in response to the treatments,with two less acidic, clay/clay loam sites showingalmost total retention of added NH4 +, whilstnearly 75% of the added N was leached asNH4 + at the acid sandy soils. The presenceof living roots significantly reduced soil solutionNO3 - and associated cation concentrations attwo of the six sites. The very different responses of the sixsoils to increased (NH4)2SO4deposition emphasise that the establishment of N critical loadsfor forest soils need to allow for differences in N storagecapacity and nitrification potential.
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