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  • 1
    Language: English
    In: Geoderma, 01 April 2016, Vol.267, pp.112-122
    Description: Our knowledge about the effect of single-tree influence areas on the physicochemical properties of the underlying mineral soil in forest ecosystems is still limited. This restricts our ability to adequately estimate future changes in soil functioning due to forest management practices. We studied the stand scale spatial variation of different soil organic matter species investigated by C NMR spectroscopy, lignin phenol and neutral sugar analysis under an unmanaged mountainous high-elevation Norway spruce ( .) forest in central Europe. Multivariate geostatistical approaches were applied to relate the spatial patterns of the different soil organic matter species to topographic parameters, bulk density, oxalate- and dithionite-extractable iron, pH, and the impact of tree distribution. Soil samples were taken from the mineral top soil. Generally, the stand scale distribution patterns of different soil organic matter compounds could be divided into two groups: Those compounds, which were significantly spatially correlated with topography/altitude and those with small scale spatial pattern (range ≤ 10 m) that was closely related to tree distribution. The concentration of plant-derived soil organic matter components, such as lignin, at a given sampling point was significantly spatially related to the distance of the nearest tree (p ≤ 0.05). In contrast, the spatial distribution of mainly microbial-derived compounds (e.g. galactose and mannose) could be attributed to the dominating impact of small-scale topography and the contribution of poorly crystalline iron oxides that were significantly larger in the central depression of the study site compared to crest and slope positions. Our results demonstrate that topographic parameters dominate the distribution of overall topsoil organic carbon (OC) stocks at temperate high-elevation forest ecosystems, particularly in sloped terrain. However, trees superimpose topography-controlled OC biogeochemistry beneath their crown by releasing litter and changing soil conditions in comparison to open areas. This may lead to distinct zones with different mechanisms of soil organic matter degradation and also stabilization in forest stands.
    Keywords: Tree–Soil Interactions ; Spatial Heterogeneity ; Zone of Tree Influence ; Soil Organic Matter Composition ; Agriculture
    ISSN: 0016-7061
    E-ISSN: 1872-6259
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  • 2
    In: Freshwater Biology, April 2017, Vol.62(4), pp.807-818
    Description: The quantification of periphyton growth in situ poses numerous difficulties. The RNA/DNA ratio is widely used as a growth indicator in marine ecology. We tested its applicability as a growth indicator of periphyton in streams of different sizes. Periphyton‐covered stones sampled from two different watercourses during two seasons were exposed in laboratory flumes to different light levels to induce different growth rates. The relationship between rate of biomass accrual and RNA/DNA ratio was analysed by measuring the chlorophyll‐a content and the RNA and DNA content of total nucleic acid extract of the periphyton respectively. The RNA/DNA ratios showed a linear relationship with the biomass accrual at all sampling times. The slopes of these relationships varied significantly between the two watercourses, but not between seasons within the same watercourse. These results indicate that the RNA/DNA ratio can be used as a growth indicator for the periphyton studied here. We recommend that it be used to detect differences in growth rate of the same periphyton community either over time or between different treatments in ecological or ecotoxicological experiments. However, for long‐term monitoring studies, we recommend taxonomic analyses of the assemblages because the observed differences in the relationship between the RNA/DNA ratio and growth rate might be attributed to community structure differences in the assemblages.
    Keywords: Growth Indicator ; Growth Rate ; Periphyton ; Rna / Dna Ratio ; Stream
    ISSN: 0046-5070
    E-ISSN: 1365-2427
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  • 3
    Language: English
    In: Plant and Soil, 2014, Vol.381(1), pp.95-110
    Description: Background and aims Differences in chemical composition of root compounds and root systems among tree species may affect organic matter (OM) distribution, source and composition in forest soils. The objective of this study was to elucidate the contribution of species specific cutin and suberin biomarkers as proxies for shoot- and root-derived organic carbon (OC) to soil OM at different depths with increasing distance to the stems of four different tree species. Methods The contribution of cutin- and suberin-derived lipids to OM in a Cutanic Alisol was analyzed with increasing soil depth and distance to the stems of Fagus sylvatica L., Picea abies (L.) Karst., Quercus robur L. and Pseudotsuga menziesii (Mirb.) Franco. Cutin and suberin monomers of plants and soils were analyzed by alkaline hydrolysis and subsequent gas chromatography-mass spectrometry. Results The amount and distribution of suberin-derived lipids in soil clearly reflected the specific root system of the different tree species. The amount of cutin-derived lipids decreased strongly with soil depth, indicating that the input of leaf/needle material is restricted to the topsoil. In contrast to the suberin-derived lipids, the spatial pattern of cutin monomer contribution to soil OM did not depend on tree species. Conclusions Our results document the importance of tree species as a main factor controlling the composition and distribution of OM in forest soils. They reveal the impact of tree species on root-derived OM distribution and the necessity to distinguish among different zones when studying soil OM storage in forests. Keywords Biomarkers * Cutin * Suberin * Depth profile * Subsoil
    Keywords: Biomarkers ; Cutin ; Suberin ; Depth profile ; Subsoil
    ISSN: 0032-079X
    E-ISSN: 1573-5036
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  • 4
    Language: English
    In: Plant and Soil, 2013, Vol.365(1), pp.93-114
    Keywords: Biomarkers ; Carbohydrates ; Depth profile ; GM/AX ratio ; Folic Histosols ; Tangelhumus
    ISSN: 0032-079X
    E-ISSN: 1573-5036
    Source: Springer Science & Business Media B.V.
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  • 5
    Language: English
    In: Chemosphere, February 2016, Vol.145, pp.163-173
    Description: The aim of this study was to analyze the environmental fate of the fungicide boscalid in a sandy soil. Boscalid was applied in spring 2010/11 to a cropland site in western Germany. Three years after second application 65 undisturbed soil samples were taken. Boscalid was extracted using accelerated solvent extraction (ASE). Boscalid contents in the plough horizon ranged between 0.12 and 0.53 with a field mean of 0.20 ± 0.09 μg kg . These contents were considerably lower compared to calculation using literature values, whereby a concentration of 16.89 μg kg was expected assuming a literature value of 345 days. Therefore, the measured field boscalid concentration only yields 1.2% of the expected value. To test whether the unknown extraction efficiency, losses from spray drift and interception can explain the mismatch between calculated and measured concentrations all these uncertainties were taken into account into calculations, but field concentrations and were still lower as expected. Leaching to deeper horizons was also studied but could not explain the discrepancy either. Moreover, a short-term incubation experiment using C labelled boscalid revealed also shorter values of 297–337 compared to the 345 days taken from literature. However, this value is still considerably larger compared to the 104–224 days that were calculated based on the field experiment. Our results indicate that boscalid dissipation under field conditions is much faster at agricultural sites with sandy soil type as expected from laboratory incubation experiments.
    Keywords: Pesticide ; Dissipation ; Field Experiment ; Batch Experiment ; Boscalid ; Chemistry ; Ecology
    ISSN: 0045-6535
    E-ISSN: 1879-1298
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  • 6
    Language: English
    In: Soil Biology and Biochemistry, 2007, Vol.39(2), pp.655-668
    Description: Long-term effects of forest disturbance 25 yr ago on lignin and non-cellulosic polysaccharide pools in an unmanaged high-elevation Norway spruce ( L. [Karst.]) forest were investigated by comparing three dieback sites with three adjacent control sites with non-infested spruce on identical soils. Samples were taken from the forest floor and the mineral soil; one Ah horizon sample per site was physically fractionated into density and particle size fractions. Additionally, changes in the above- and belowground input of lignin and non-cellulosic polysaccharides after forest dieback were quantified. Lignin and its degree of structural alteration in plant and soil samples were assessed by CuO oxidation and subsequent analysis of the lignin phenols. Non-cellulosic polysaccharides were determined after hydrolysis with trifluoroacetic acid (TFA), derivatisation of their neutral sugar monomers by reduction to alditols, and subsequent acetylation. The total plant-derived input of lignin and non-cellulosic polysaccharides to the soil was similar for the dieback and the control sites. The chemical composition of the input has changed considerably after forest dieback, as shown by significantly higher syringyl/vanillyl (S/V) ratios and significantly lower (galactose+mannose)/(arabinose+xylose) (GM/AX) ratios. This indicates a changed plant input and a higher contribution of microbial sugars. Contents of lignin phenols in the forest floor and coarse particle size fractions of the A horizons were significantly smaller at the dieback sites ( 〈0.01). Moreover, larger acid-to-aldehyde ratios of vanillyl units (Ac/Al) indicated an increased degree of lignin phenol alteration. Also contents of neutral sugars were significantly ( 〈0.01) smaller in the forest floor, but not in the A horizons of the dieback sites. The GM/AX mass ratios as well as the (rhamnose+fucose)/(arabinose+xylose) (RF/AX) ratios in the forest floor and coarse particle size fractions of the mineral topsoil were significantly ( 〈0.01) larger after forest dieback, indicating a larger relative contribution of microbial sugars. In general, the lignin phenol and neutral sugar pools of all three soil types exhibited similar response patterns to the changed site conditions. Our results demonstrate that the lignin and neutral sugar pools of humic topsoil horizons are highly sensitive to forest disturbances. However, the two compounds show different patterns in the mineral soil, with the major neutral sugar pool being stabilized against changes whereas the lignin phenol pool decreases significantly.
    Keywords: Forest Soils ; Particle Size Fractions ; Alkaline Cuo-Oxidation ; Soil Carbohydrates ; Polysaccharides ; Canopy Loss ; Soil Organic Carbon ; Agriculture ; Chemistry
    ISSN: 0038-0717
    E-ISSN: 1879-3428
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  • 7
    Language: English
    In: Journal of Soils and Sediments, 2013, Vol.13(9), pp.1579-1588
    Description: Purpose: Nutrient release, soil wettability, water binding, and matrix rigidity of soil organic matter (SOM) can be affected by cross-links between segments of SOM, cations, and water molecule bridges (WaMB). Not all cation effects on SOM can be explained with the currently accepted idea that multivalent cations cross-link organic matter segments via direct cation bridges (CaB). The objective was to understand these interactions and their effect on SOM matrix rigidity and wettability. Materials and methods: We modified cation composition of two peats and an organic surface layer (OSL) using cation exchange resin to remove cations and solutions of Na super(+), Ca super(2+), or Al super(3+) to enrich samples with cations. SOM matrix rigidity was determined at 4 and 〉8 weeks after treatment via the WaMB transition temperature T*, using differential scanning calorimetry. Wettability was measured via sessile drop contact angle (CA). Results and discussion: The effect of cation removal on T* depended on cation exchange capacity and initial cation content. Cation addition to OSL increased T*. This effect increased with increasing cation loading and valency, and T* correlated with CA. Classical cross-linking can neither explain the higher heterogeneous matrix of Ca-treated than Al-treated samples nor the aging-induced convergence of T* for different cations and concentrations. The latter is likely due to interaction between CaB and WaMB in SOM. Conclusions: Associations of CaB and WaMB evolve slowly and form a supramolecular network in SOM. Those dynamic associations can fix molecular arrangements inducing water repellency and increase kinetic barriers for the release and uptake of water and nutrients from aged soil.
    Keywords: Cross-links ; Differential scanning calorimetry ; Matrix rigidity ; Multivalent cation ; Soil organic matter ; Water molecule bridges (WaMB) ; Water repellency
    ISSN: 1439-0108
    E-ISSN: 1614-7480
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  • 8
    Language: English
    In: Plant and Soil, 1 April 2013, Vol.365(1/2), pp.93-114
    Description: Background and aims We investigated the potential of non-cellulosic polysaccharides (NCP) as biomarkers to identify the plant types that dominate present and past litter input into organic surface covers on calcareous Alpine soils and to reveal historic vegetation changes. Methods At two sites in the Alps, NCP monomers were quantified in different organs of site-dominating plants, the Oa horizon of four Folie Leptosols, and different sections of thick organic surface layers of four Folie Histosols on calcareous bedrock. Results The dominating plant types at our study sites differ markedly in their NCP composition and (galactose + mannose)/(arabinose + xylose) [GM/AX] ratio (grasses and sedges: 0.2; dicots Fagus and Vaccinium: 0.2-0.6; conifers Abies, Picea, Pinus: 0.7-2.4; mosses: 5). For all except one soil, the NCP signature of the uppermost Oa horizon reflects the present vegetation. For all Histosol O horizons, NCP signatures indicate a dominance of conifer litter throughout their development (up to 1,500 years). Different NCP and GM/AX depth profiles reflect specific patterns of O layer genesis. Conclusions NCP and GM/AX depth profiles in organic surface covers of soils provide important information about dominating litter sources in the past and can be valuable tools to reveal historic vegetation and/or land use changes.
    Keywords: Biological sciences -- Agriculture -- Agricultural sciences ; Biological sciences -- Biology -- Botany ; Biological sciences -- Biology -- Botany ; Biological sciences -- Agriculture -- Agricultural sciences ; Biological sciences -- Agriculture -- Agricultural sciences ; Physical sciences -- Chemistry -- Chemical compounds ; Biological sciences -- Agriculture -- Agricultural sciences ; Biological sciences -- Biology -- Botany ; Biological sciences -- Agriculture -- Agricultural sciences ; Biological sciences -- Agriculture -- Agricultural sciences
    ISSN: 0032079X
    E-ISSN: 15735036
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  • 9
    Language: English
    In: Geoderma, December 2014, Vol.235-236, pp.146-153
    Description: Enrichment of C in SOM with soil depth is related to interacting processes influenced by temperature and precipitation. Our objectives were to derive climate effects on patterns of vertical δ C values of soil organic matter (SOM) while minimizing the effect of confounding variables. We investigated vertical changes in δ C values of SOM in 1-cm depth intervals in silvicultural mature beech ( L.) forest ecosystems in northern Rhineland-Palatinate across gradients of MAT (7.9 to 9.7 °C mean annual temperature) and MAP (607 to 1085 mm mean annual precipitation) in winter 2011. Forest stands (n = 10) were chosen based on data sets provided by the Rhineland-Palatinate Forest Administration so that variations in these gradients occurred while other environmental factors like physico-chemical soil properties, tree species, stand age, exposition and precipitation (for the temperature gradient) or temperature (for the precipitation gradient) did not differ among study sites. From litter down to the mineral soil at 10 cm depth, soil organic carbon (SOC) content decreased (47.5 ± SE 0.1% to 2.5 ± 0.1%) while the δ C values increased (− 29.4 ± 0.1‰ to − 26.1 ± 0.1‰). Litter of sites under higher MAP/lower MAT had lower δ C values which was in line with literature data on climate driven plant physiological process. To compare the dimension of the vertical C enrichment, δ C values were regressed linearly against log-transformed carbon contents yielding absolute values of these slopes (beta). Beta values ranged between 0.6 and 4.5 (range of r from − 0.7 to − 1.0; p 〈 0.01). Due to an assumed decay continuum and similar variations of δ C values in litter and in 10 cm depth, we conclude that effects on isotope composition in the Oi layer continue vertically and therefore, δ C values in litter do not solely control beta values. Beta values decreased with increasing MAT (r = − 0.83; p 〈 0.05). Reduced soil moisture and therefore both, reduced microbial activity and reduced downward transport of microbial cycled DOM (= C enriched) might be responsible for less pronounced δ C depth profiles in case of high temperatures. Greater C:N ratios (lower degradability) of the litter under higher temperatures likely contributed to these depth trends. Beta values increased with increasing MAP (r = 0.73; p 〈 0.05). We found decreasing C:N ratios in the mineral soil that possibly indicates higher decomposition under higher precipitation. Exclusion of the organic layers from linear regressions indicated a stronger impact of MAP on the development of δ C depth profiles. Our results confirm temperature and precipitation effects on δ C depth profiles and indicate stronger C enrichment under lower MAT/higher MAP. Therefore, time series of vertical δ C depth profiles might provide insights into climate change effects.
    Keywords: Depth Profile ; Fagus Sylvatica ; Stable Isotope ; Carbon Decomposition ; Microbial Activity ; Agriculture
    ISSN: 0016-7061
    E-ISSN: 1872-6259
    Source: ScienceDirect Journals (Elsevier)
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  • 10
    Language: English
    In: Geoderma, 15 October 2017, Vol.304, pp.1-3
    Keywords: Agriculture
    ISSN: 0016-7061
    E-ISSN: 1872-6259
    Source: ScienceDirect Journals (Elsevier)
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