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  • 1
    Language: English
    In: Global change biology, 2011, Vol.17(7), pp.2428-2443
    Description: Here, we report site-to-site variability and 12-14 year trends of dissolved organic carbon (DOC) from organic layers and mineral soils of 22 forests in Bavaria, Germany. DOC concentrations in the organic layer were negatively correlated with mean annual precipitation and elevation whereas air temperature had a positive effect on DOC concentrations. DOC fluxes in subsoils increased by 3 kg ha⁻¹ yr⁻¹ per 100 mm precipitation or per 100 m elevation. The highest DOC concentrations were found under pine stands with mor humus. Average DOC concentrations in organic layer leachates followed the order: pine〉oak〉spruce〉beech. However, the order was different for mean DOC fluxes (spruce〉pine〉oak〉beech) because of varying precipitation regimes among the forest types. In 12 of 22 sites, DOC concentrations of organic layer leachates significantly increased by 0.5 to 3.1 mg C L⁻¹ yr⁻¹ during the sampling period. The increase in DOC concentration coincided with decreasing sulfate concentration, indicating that sulfate concentration is an important driver of DOC solubility in the organic layer of these forest sites. In contrast to the organic layer, DOC concentrations below 60 cm mineral soil depth decreased by 〈0.1-0.4 mg C L⁻¹ yr⁻¹ at eight sites. The negative DOC trends were attributed to (i) increasing adsorption of DOC by mineral surfaces resulting from desorption of sulfate and (ii) increasing decay of DOC resulting from decreasing stabilization of DOC by organo-Al complexes. Trends of DOC fluxes from organic layers were consistent with those of DOC concentrations although trends were only significant at seven sites. DOC fluxes in the subsoil were with few exceptions small and trends were generally not significant. Our results suggest that enhanced mobilization of DOC in forest floors contributed to the increase of DOC in surface waters while mineral horizons did not contribute to increasing DOC export of forest soils. ; p. 2428-2443.
    Keywords: Forest Soils ; Desorption ; Air Temperature ; Dissolved Organic Carbon ; Leachates ; Mineral Soils ; Surface Water ; Atmospheric Precipitation ; Correlation ; Forest Types ; Adsorption ; Solubility ; Forest Litter ; Temporal Variation ; Soil Depth ; Humus ; Mor
    ISSN: 1354-1013
    E-ISSN: 13652486
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  • 2
    Language: English
    In: Proceedings of the National Academy of Sciences of the United States of America, 24 November 2015, Vol.112(47), pp.14647-51
    Description: The desiccation of upper soil horizons is a common phenomenon, leading to a decrease in soil microbial activity and mineralization. Recent studies have shown that fungal communities and fungal-based food webs are less sensitive and better adapted to soil desiccation than bacterial-based food webs. One reason for a better fungal adaptation to soil desiccation may be hydraulic redistribution of water by mycelia networks. Here we show that a saprotrophic fungus (Agaricus bisporus) redistributes water from moist (-0.03 MPa) into dry (-9.5 MPa) soil at about 0.3 cm ⋅ min(-1) in single hyphae, resulting in an increase in soil water potential after 72 h. The increase in soil moisture by hydraulic redistribution significantly enhanced carbon mineralization by 2,800% and enzymatic activity by 250-350% in the previously dry soil compartment within 168 h. Our results demonstrate that hydraulic redistribution can partly compensate water deficiency if water is available in other zones of the mycelia network. Hydraulic redistribution is likely one of the mechanisms behind higher drought resistance of soil fungi compared with bacteria. Moreover, hydraulic redistribution by saprotrophic fungi is an underrated pathway of water transport in soils and may lead to a transfer of water to zones of high fungal activity.
    Keywords: Carbon Mineralization ; Drought ; Hydraulic Redistribution ; Saprotrophic Fungi ; Agaricus -- Metabolism ; Carbon -- Metabolism ; Minerals -- Metabolism ; Soil -- Chemistry ; Water -- Chemistry
    ISSN: 00278424
    E-ISSN: 1091-6490
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  • 3
    In: Ecological Applications, March 2011, Vol.21(2), pp.391-401
    Description: We simulated the effect of prolonged dry summer periods by lowering the water table on three manipulation plots (D) in a minerotrophic fen in southeastern Germany in three years (2006–2008). The water table at this site was lowered by drainage and by excluding precipitation; three nonmanipulated control plots (C) served as a reference. We found no significant differences in soil respiration (), gross primary production (GPP), or aboveground respiration () between the C and D plots in any of the measurement years. The water table on the control plots was naturally low, with a median water table (2006–2008) of 8 cm below the surface, and even lower during summer when respiratory activity was highest, with median values (C) between 11 and 19 cm below the surface. If it is assumed that oxygen availability in the uppermost 10 cm was not limited by the location of the water table, manipulative lowering of the water table most likely increased oxygen availability only in deeper peat layers where we expect to be limited by poor substrate quality rather than anoxia. This could explain the lack of a manipulation effect. In a second approach, we estimated the influence of the water table on irrespective of treatment. The results showed a significant correlation between and water table, but with decreasing at lower water tables rather than increasing. We thus conclude that decomposition in the litter layer is not limited by waterlogging in summer, and deeper peat layers bear no significant decomposition potential due to poor substrate quality. Consequently, we do not expect enhanced C losses from this site due to increasing frequency of dry summers. Assimilation and respiration of aboveground vegetation were not affected by water table fluctuations between 10 and 〉60 cm depth, indicating the lack of stress resulting from either anoxia (high water table) or drought (low water table).
    Keywords: Climate Change ; Co 2 Emissions And Uptake ; Ecosystem Manipulation ; Fen ; Peat Decomposition ; Southeastern Germany ; Water Table Lowering
    ISSN: 1051-0761
    E-ISSN: 1939-5582
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  • 4
    Language: English
    In: Soil Biology and Biochemistry, December 2017, Vol.115, pp.516-525
    Description: Woody debris (WD) represents a litter input to forest soils, but its impact on carbon (C) cycling and the fungal community in the underlying forest floor is unclear. Here, we assessed the effect of WD of eight tree species differing in wood quality on CO production, microbial biomass C and fungal community of an Oe horizon from a Norway spruce forest in a combined field-laboratory study. The 78-day incubation at 20 °C comprised three treatments: Oe, WD, and Oe + WD. In the Oe treatment, the Oe horizon was previously covered with WD for 1.5 years in the Norway spruce forest. Oe horizon from control subplots that was not covered with WD in past years served as control (Oe treatment). WD originated from the 1.5-year-old field study and was either separately incubated (WD treatment) or together with Oe horizon from control subplots (Oe + WD treatment). In the Oe treatment, CO production and microbial biomass C were significantly higher in the Oe horizon under fast decomposing WD of , and than in the Oe control. The effect of WD on the Oe horizon was even stronger in the Oe + WD treatment after separation of both substrates (day 80). CO production and microbial biomass C were 3–6 times or 3–5 times higher, respectively, than the control, either due to ingrowth of wood decomposing fungi or growth of autochthonous microbes in the Oe. Further, WD increased the molar C:N ratio of the Oe horizons by 1.2 units in the Oe + WD treatment. Glucose addition reduced or did not affect the CO production of WD, indicating that wood decomposing microorganisms were not C-limited. The fungal communities in the Oe + WD treatment were altered in both substrates, and differed primarily between angiosperm and gymnosperm WD. Fungi preferably occurring in samples with strong increase in CO production were native Oe fungi, indicating that invasion by wood fungi had little direct effect on C mineralization in the Oe horizon. Our results suggest that WD of common tree species represents a labile C source that can accelerate the C mineralization in the Oe horizon.
    Keywords: Woody Debris ; Microbial Biomass ; Co2 Production ; Fungal Community ; Tree Species ; Agriculture ; Chemistry
    ISSN: 0038-0717
    E-ISSN: 1879-3428
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  • 5
    Language: English
    In: Plant and Soil, 2011, Vol.339(1), pp.435-445
    Description: Atmospheric inputs of acids and nitrogen (N) have altered growth and vitality of forests for decades, but there is a lack of understanding concerning the response of these forests to reduced deposition. We studied fine root parameters of a Norway spruce stand treated with reduced input (clean rain) for 13 years. Fine roots of the clean rain plot had smaller N and Al contents, however, fine roots in the subsoil were still subjected to soil acidity and Al toxicity as indicated by a fine root Ca/Al ratio of less than 0.5. The treatment effect was most pronounced in the organic layer of the clean rain plot where fine root biomass increased by 66% and the live/dead ratio of fine roots increased by more than 100%. The elevated live/dead ratio was attributed to reduced mortality and faster decomposition of fine root litter. The latter was supported by a positive relationship between live/dead ratio and manganese content of fine roots. In contrast to the organic layer, fine root biomass was not different in the mineral soil. However, at 20–40 cm fine root diameter was greater and specific root tip density was smaller than in the topsoil likely because of strong N limitation as indicated by a C/N ratio of 〉50. Based on these morphological changes we postulate differing functional properties of fine roots in the organic layer and mineral soil below 20 cm depth. Further, our results suggest that Picea abies is able to adapt morphology and functional traits of its root system following reduced N availability.
    Keywords: Solling roof project ; Norway spruce ; Atmospheric deposition ; Fine roots ; Re-establishment
    ISSN: 0032-079X
    E-ISSN: 1573-5036
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  • 6
    In: Global Change Biology, November 2015, Vol.21(11), pp.4265-4277
    Description: Thermal adaptations of soil microorganisms could mitigate or facilitate global warming effects on soil organic matter (SOM) decomposition and soil CO efflux. We incubated soil from warmed and control subplots of a forest soil warming experiment to assess whether 9 years of soil warming affected the rates and the temperature sensitivity of the soil CO efflux, extracellular enzyme activities, microbial efficiency, and gross N mineralization. Mineral soil (0–10 cm depth) was incubated at temperatures ranging from 3 to 23 °C. No adaptations to long‐term warming were observed regarding the heterotrophic soil CO efflux ( warmed: 2.31 ± 0.15 μmol m s, control: 2.34 ± 0.29 μmol m s; warmed: 2.45 ± 0.06, control: 2.45 ± 0.04). Potential enzyme activities increased with incubation temperature, but the temperature sensitivity of the enzymes did not differ between the warmed and the control soils. The ratio of C : N acquiring enzyme activities was significantly higher in the warmed soil. Microbial biomass‐specific respiration rates increased with incubation temperature, but the rates and the temperature sensitivity ( warmed: 2.54 ± 0.23, control 2.75 ± 0.17) did not differ between warmed and control soils. Microbial substrate use efficiency (SUE) declined with increasing incubation temperature in both, warmed and control, soils. SUE and its temperature sensitivity ( warmed: 0.84 ± 0.03, control: 0.88 ± 0.01) did not differ between warmed and control soils either. Gross N mineralization was invariant to incubation temperature and was not affected by long‐term soil warming. Our results indicate that thermal adaptations of the microbial decomposer community are unlikely to occur in C‐rich calcareous temperate forest soils.
    Keywords: Enzyme Activities ; Gross N Mineralization ; Soil Co 2 Efflux ; Soil Warming ; Substrate Use Efficiency ; Thermal Adaptation
    ISSN: 1354-1013
    E-ISSN: 1365-2486
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  • 7
    Language: English
    In: Soil Biology and Biochemistry, Feb, 2014, Vol.69, p.320(8)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.soilbio.2013.11.014 Byline: Marianne Schutt, Werner Borken, Oliver Spott, Claus Florian Stange, Egbert Matzner Abstract: Climate models predict warmer winter in temperate regions, but little is known about the temperature sensitivity of soil carbon (C) and nitrogen (N) mineralization at low temperatures. Here, we assess the temperature sensitivities of gross ammonification, gross nitrification, C and net N mineralization of top soil horizons, under a European beech and a Norway spruce temperate forest. We tested the hypotheses that (1) substrate quality affects the temperature sensitivity of C and N mineralization and (2) that temperature sensitivity of C mineralization is higher than of gross ammonification. Soil incubations were conducted at constant temperatures of -4, -1, +2, +5 and +8 [degrees]C. Gross ammonification and nitrification were measured by the.sup.15N pool dilution technique. Temperature sensitivities of C, gross and net N mineralization were calculated using the Arrhenius equation and C mineralization was taken as proxy for substrate quality. Gross ammonification and C mineralization was much larger in the beech than in the spruce soil, while gross nitrification was in the same order of magnitude. Gross ammonification, nitrification and C mineralization almost ceased at -4 [degrees]C, but already increased at -1 [degrees]C. Net ammonification in Oi/Oe horizons was low at -4 and -1 [degrees]C and increased strongly between +2 and +8 [degrees]C. Net nitrification was low in both soils, but increased in the spruce soil at temperatures 〉2 [degrees]C whereas no temperature response occurred in the beech soil. Apparent Q.sub.10 values of gross ammonification and C mineralization in the temperature range of -4 to +8 [degrees]C were in the range of 3-18. Q.sub.10 were lowest in soil horizons of low substrate quality. The ratio of C mineralization to gross ammonification varied between 0.5 and 2.9, suggesting preferential mineralization of N rich organic substrates or rapid turnover of the N pool in microbial biomass. Rising winter temperatures might have substantial effects on net N mineralization, but effects decrease with soil depth, likely due to decreasing substrate quality of soil organic matter. Author Affiliation: (a) Department of Soil Ecology, University of Bayreuth, 95448 Bayreuth, Germany (b) Department of Soil Physics, Helmholtz Center for Environmental Research, UFZ, 06120 Halle/Saale, Germany (c) Bundesanstalt fur Geowissenschaften und Rohstoffe, Fachbereich B2.4 "Boden als Ressource - Stoffeigenschaften und -dynamik", 30655 Hannover, Germany Article History: Received 21 June 2013; Revised 7 November 2013; Accepted 14 November 2013
    Keywords: Soil Biology -- Analysis ; Nitrification -- Analysis ; Soil Ecology -- Analysis ; Forest Soils -- Analysis ; Soil Carbon -- Analysis
    ISSN: 0038-0717
    Source: Cengage Learning, Inc.
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  • 8
    Language: English
    In: Forest Ecology and Management, Dec 15, 2013, Vol.310, p.110(10)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.foreco.2013.08.006 Byline: Michael Goisser, Ulrich Zang, Egbert Matzner, Werner Borken, Karl-Heinz Haberle, Rainer Matyssek Abstract: acents Response of juvenile European beech upon transplant to heterogeneous light and water availability. acents Plant response was examined along the gradients of light and water availability. acents High light acclimation exacerbated productivity decline under drought. acents Progressive acclimation to shade and drought mitigated productivity decline within the study period. Article History: Received 18 April 2013; Revised 4 August 2013; Accepted 5 August 2013
    Keywords: Water ; Industrial Productivity
    ISSN: 0378-1127
    Source: Cengage Learning, Inc.
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  • 9
    In: Global Change Biology, April 2009, Vol.15(4), pp.781-781
    Description: To authenticate to the full-text of this article, please visit this link: http://dx.doi.org/10.1111/j.1365-2486.2009.01893.x Byline: WERNER BORKEN (*), EGBERT MATZNER (*) Author Affiliation: (*)Department of Soil Ecology, University of Bayreuth, 95440 Bayreuth, Germany Article note: Correspondence: Werner Borken, tel. +49 921 555 741, fax +49 921 555 799, e-mail: werner.borken@uni-bayreuth.de
    Keywords: Soil Ecology ; Soils;
    ISSN: 1354-1013
    E-ISSN: 1365-2486
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  • 10
    In: Global Change Biology, April 2009, Vol.15(4), pp.808-824
    Description: In the next decades, many soils will be subjected to increased drying/wetting cycles or modified water availability considering predicted global changes in precipitation and evapotranspiration. These changes may affect the turnover of C and N in soils, but the direction of changes is still unclear. The aim of the review is the evaluation of involved mechanisms, the intensity, duration and frequency of drying and wetting for the mineralization and fluxes of C and N in terrestrial soils. Controversial study results require a reappraisal of the present understanding that wetting of dry soils induces significant losses of soil C and N. The generally observed pulse in net C and N mineralization following wetting of dry soil (hereafter wetting pulse) is short‐lived and often exceeds the mineralization rate of a respective moist control. Accumulated microbial and plant necromass, lysis of live microbial cells, release of compatible solutes and exposure of previously protected organic matter may explain the additional mineralization during wetting of soils. Frequent drying and wetting diminishes the wetting pulse due to limitation of the accessible organic matter pool. Despite wetting pulses, cumulative C and N mineralization (defined here as total net mineralization during drying and wetting) are mostly smaller compared with soil with optimum moisture, indicating that wetting pulses cannot compensate for small mineralization rates during drought periods. Cumulative mineralization is linked to the intensity and duration of drying, the amount and distribution of precipitation, temperature, hydrophobicity and the accessible pool of organic substrates. Wetting pulses may have a significant impact on C and N mineralization or flux rates in arid and semiarid regions but have less impact in humid and subhumid regions on annual time scales. Organic matter stocks are progressively preserved with increasing duration and intensity of drought periods; however, fires enhance the risk of organic matter losses under dry conditions. Hydrophobicity of organic surfaces is an important mechanism that reduces C and N mineralization in topsoils after precipitation. Hence, mineralization in forest soils with hydrophobic organic horizons is presumably stronger limited than in grassland or farmland soils. Even in humid regions, suboptimal water potentials often restrict microbial activity in topsoils during growing seasons. Increasing summer droughts will likely reduce the mineralization and fluxes of C and N whereas increasing summer precipitation could enhance the losses of C and N from soils.
    Keywords: C Mineralization ; Drying ; Nitrate Leaching ; N Mineralization ; Precipitation ; Soil Moisture ; Soil Organic Carbon ; Soil Respiration ; Wetting
    ISSN: 1354-1013
    E-ISSN: 1365-2486
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