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  • 1
    Language: English
    In: Agriculture, Ecosystems and Environment, Jan 15, 2013, Vol.165, p.88(10)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.agee.2012.12.012 Byline: Christian Poll (a), Sven Marhan (a), Florian Back (a), Pascal A. Niklaus (b), Ellen Kandeler (a) Keywords: Climate change; Soil warming; Precipitation; Soil moisture; Soil respiration; Arable soil Abstract: a* We present one of the first climate change experiments in an agricultural ecosystem. a* The HoCC experiment combines soil warming and altered precipitation. a* Water limitation reduced microbial biomass and soil respiration in the first summer. a* Soil warming increased soil respiration in the second year by 27%. a* Moisture regime of soils largely determines their function as C sources or C sinks. Author Affiliation: (a) Institute of Soil Science and Land Evaluation, Soil Biology Section, University of Hohenheim, Emil-Wolff-Stra[sz]e 27, 70599 Stuttgart, Germany (b) Institute of Evolutionary Biology and Environmental Studies, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland Article History: Received 30 April 2012; Revised 21 December 2012; Accepted 24 December 2012
    Keywords: Soil Moisture -- Environmental Aspects ; Agroecosystems -- Environmental Aspects ; Soil Microbiology -- Environmental Aspects ; Global Temperature Changes -- Environmental Aspects ; Soil Heating -- Environmental Aspects ; Precipitation (Meteorology) -- Environmental Aspects ; Evolutionary Biology -- Environmental Aspects
    ISSN: 0167-8809
    Source: Cengage Learning, Inc.
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  • 2
    Language: English
    In: Food Chemistry, 01 February 2013, Vol.136(3-4), pp.1470-1477
    Description: ► One of the first experiments combining temperature and precipitation is presented. ► Elevated temperature affects grain quality more severely than changes in rainfall. ► Notably, TGW, lipids, Al and NSCs (except for maltose) were decreased in barley. ► Several proteinogenic amino acids were increased due to elevated temperature. ► Future temperature increase will change nutritional value and processing of grains. Spring barley was grown in a field experiment under moderately elevated soil temperature and changed summer precipitation (amount and frequency). Elevated temperature affected the performance and grain quality characteristics more significant than changes in rainfall. Except for the decrease in thousand grain weight, warming had no impacts on aboveground biomass and grain yield traits. In grains, several proteinogenic amino acids concentrations were increased, whereas their composition was only slightly altered. Concentration and yield of total protein remained unaffected under warming. The concentrations of total non-structural carbohydrates, starch, fructose and raffinose were lower in plants grown at high temperatures, whereas maltose was higher. Crude fibre remained unaffected by warming, whereas concentrations of lipids and aluminium were reduced. Manipulation of precipitation only marginally affected barley grains: amount reduction increased the concentrations of several minerals (sodium, copper) and amino acids (leucine). The projected climate changes may most likely affect grain quality traits of interest for different markets and utilisation requirements.
    Keywords: Barley ; Temperature Increase ; Precipitation Pattern ; Grain Yield ; Grain Quality ; Climate Change ; Chemistry ; Diet & Clinical Nutrition ; Economics
    ISSN: 0308-8146
    E-ISSN: 1873-7072
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  • 3
    In: Global Change Biology, January 2018, Vol.24(1), pp.e318-e334
    Description: Global warming will likely enhance greenhouse gas () emissions from soils. Due to its slow decomposability, biochar is widely recognized as effective in long‐term soil carbon (C) sequestration and in mitigation of soil emissions. In a long‐term soil warming experiment (+2.5 °C, since July 2008) we studied the effect of applying high‐temperature biochar (0, 30 t/ha, since August 2013) on emissions and their global warming potential () during 2 years in a temperate agroecosystem. Crop growth, physical and chemical soil properties, temperature sensitivity of soil respiration (), and metabolic quotient () were investigated to yield further information about single effects of soil warming and biochar as well as on their interactions. Soil warming increased total emissions by 28% over 2 years. The effect of warming on soil respiration did not level off as has often been observed in less intensively managed ecosystems. However, the temperature sensitivity of soil respiration was not affected by warming. Overall, biochar had no effect on most of the measured parameters, suggesting its high degradation stability and its low influence on microbial C cycling even under elevated soil temperatures. In contrast, biochar × warming interactions led to higher total NO emissions, possibly due to accelerated N‐cycling at elevated soil temperature and to biochar‐induced changes in soil properties and environmental conditions. Methane uptake was not affected by soil warming or biochar. The incorporation of biochar‐C into soil was estimated to offset warming‐induced elevated emissions for 25 years. Our results highlight the suitability of biochar for C sequestration in cultivated temperate agricultural soil under a future elevated temperature. However, the increased NO emissions under warming limit the mitigation potential of biochar. In a long‐term soil warming experiment, we found elevated soil temperature to enhance the Global Warming Potential (GWP) of soil greenhouse gas emissions over 2 years, while biochar had no effect. Although biochar did not reduce GHG emissions from warmed soil, its sequestration was estimated to offset global warming‐induced elevated GHG emissions of more than two decades. However, the increased NO emissions from warmed biochar‐amended soil limits the GHG mitigation potential of biochar.
    Keywords: Agroecosystem ; Biochar ; Carbon Dioxide ; Carbon Sequestration ; Methane ; Nitrous Oxide ; Soil Warming ; Temperature Sensitivity
    ISSN: 1354-1013
    E-ISSN: 1365-2486
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  • 4
    Language: English
    In: Soil Biology and Biochemistry, February 2017, Vol.105, pp.138-152
    Description: While habitat conditions influencing the abundance of microorganisms in topsoil are well known, these dynamics have been largely unexplored in deeper soil horizons. We investigated the effects of different substrate availabilities and environmental conditions on microbial community composition and carbon flow into specific groups of microorganisms in subsoils using a reciprocal soil transfer experiment within an acid and sandy Dystric Cambisol from a ∼100-year old European beech ( L.) forest in Lower Saxony, Germany. Containers filled with subsoil from 10 to 20 cm (SUB20) and 110 to 120 cm (SUB120) soil depths and with additions of different amounts of C labelled cellulose (1% and 5% of the respective organic carbon content of both soil layers) were exposed either in their home field environment or transferred reciprocally between SUB20 and SUB120 horizons for periods of one, four and twelve months. During the exposure of twelve months, C accumulated up to 15 percent in total microbial biomass and up to 25 percent in fungal PLFAs. Similar microbial C incorporation rates in SUB20 samples located at either 20 or 120 cm depth indicated comparable microclimatic conditions in both soil environments with no depth-dependent effects on the decomposer communities. While low nitrogen availability (when primary C-limitation was alleviated) and water content limited bacterial growth and activity at both depths, fungal abundance and activity were less affected due to their ability to efficiently exploit resources in surrounding soil by hyphal growth and higher drought resistance. Consequently, bacterial PLFAs (phospholipid fatty acids) incorporated less C than fungi. The relatively high, from 1% to 5% cellulose addition linearly increased, C incorporation rates in SUB120 samples at 120 cm depth clearly showed the potential of efficient carbon turnover in deeper soil layers. Spatial separation between subsoil microorganisms and their substrates may therefore be an important factor influencing carbon accumulation in subsoil.
    Keywords: Carbon Cycle ; Stable Isotope Probing ; Phospholipid Fatty Acids (Plfas) ; Soil Microorganisms ; Micro-Environment ; Micro-Climate ; Agriculture ; Chemistry
    ISSN: 0038-0717
    E-ISSN: 1879-3428
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  • 5
    Language: English
    In: Soil Biology and Biochemistry, December 2017, Vol.115, pp.187-196
    Description: Resource quality and availability modify the microbial contribution to soil organic matter turnover and formation. We created a microbial hotspot at the soil-litter interface in a microcosm experiment to better understand and integrate specific microbial habitats into C turnover models. Reciprocal transplantation of C and C litter on top of soil cores allowed us to follow C flow into specific members of the microbial food web (bacteria and fungi) and to calculate the turnover times of litter-derived C in these microorganisms at three different stages of maize litter decomposition; early stage (0–4 days), intermediate stage (5–12 days) and later stage (29–36 days). Litter age influenced the incorporation rate of C into bacteria and fungi and subsequent turnover in phospholipid fatty acid (PLFA) biomarkers. When fresh litter was applied, both fungi and bacteria were able to assimilate labile litter C in the early stage of decomposition, while lower substrate quality in the intermediate stage of decomposition promoted fungal utilization. Utilization of complex litter C sources was minor in both fungi and bacteria in the later stage of decomposition. Different bacterial substrate utilization strategies were reflected by either a decline of the isotopic signal after exchange of C by C litter or by storage and/or reuse of previously released microbial C. The mean residence time of C in the fungal PLFA 18:2ω6,9 was estimated from 46 to 32 days, which is the same or shorter time than that of bacterial PLFAs. This highlights the role of fungi in rapid turnover processes of plant residues, with implications for implementation of bacterial and fungal processes into C turnover models.
    Keywords: Soil Carbon Cycle ; 13c Pulse Labeling ; C Microbial Turnover ; Phospholipid Fatty Acids (Plfas) ; Detritusphere ; Agriculture ; Chemistry
    ISSN: 0038-0717
    E-ISSN: 1879-3428
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  • 6
    Language: English
    In: Soil Biology and Biochemistry, December 2018, Vol.127, pp.60-70
    Description: Soil microbial communities mediate soil feedbacks to climate; a thorough understanding of their response to increasing temperatures is therefore central to predict climate-induced changes in carbon (C) fluxes. However, it is unclear how microbial communities will change in structure and function in response to temperature change and to the availability of organic C which varies in complexity. Here we present results from a laboratory incubation study in which soil microbial communities were exposed to different temperatures and organic C complexity. Soil samples were collected from two land-use types differing in climatic and edaphic conditions and located in two regions in southwest Germany. Soils amended with cellobiose (CB), xylan, or coniferyl alcohol (CA, lignin precursor) were incubated at 5, 15 or 25 °C. We found that temperature predominantly controlled microbial respiration rates. Increasing temperature stimulated cumulative respiration rates but decreased total microbial biomass (total phospholipid fatty acids, PLFAs) in all substrate amendments. Temperature increase affected fungal biomass more adversely than bacterial biomass and the temperature response of fungal biomass (fungal PLFAs, ergosterol and ITS fragment) depended upon substrate quality. With the addition of CB, temperature response of fungal biomass did not differ from un-amended control soils, whereas addition of xylan and CA shifted the fungal temperature optima from 5 °C to 15 °C. These results provide first evidence that fungi which decompose complex C substrates (CA and xylan) may have different life strategies and temperature optima than fungal communities which decompose labile C substrate (CB). Gram-positive and gram-negative bacteria differed strongly in their capacity to decompose CB under different temperature regimes: gram-positive bacteria had highest PLFA abundance at 5 °C, while gram-negative bacteria were most abundant at 25 °C. Bacterial community composition, as measured by 16S rRNA gene abundance, and PLFAs showed opposite temperature and substrate decomposition trends. Using multivariate statistics, we found a general association of microbial life strategies and key members of the microbial community: oligotrophic and were associated with complex substrates and copiotrophic with labile substrates. Our study provides evidence that the response of C cycling to warming will be mediated by shifts in the structure and function of soil microbial communities.
    Keywords: Carbon Decomposition ; Substrate Quality ; Bacteria ; Fungi ; Bacterial Taxa ; Plfa ; Agriculture ; Chemistry
    ISSN: 0038-0717
    E-ISSN: 1879-3428
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  • 7
    Language: English
    In: Soil Biology and Biochemistry, December 2016, Vol.103, pp.380-387
    Description: Hydraulic redistribution (HR) of water from wet to dry soil compartments by non-differentiated mycelium was recently shown for the saprotrophic fungus . The redistributed water triggered the carbon (C) mineralization in the dry soil. The potential of other saprotrophic fungal species and their mycelia networks for HR in soils is unknown. Here, we tested the potential for HR of the mycelial cord forming species compared it to capillary water transport in a sandy soil and assessed the impact of HR on C mineralization and enzyme activities in mesocosm experiments with dry and wet soil compartments using labeled water ( H) and labeled organic substrate ( C, N). Further, we determined nitrogen (N) translocation between the soil compartments by the mycelium of and . The flow velocity of redistributed water in single hyphae of was about 0.43 cm min which is 1.5–2 times higher than in hyphae of , suggesting that cords enhance fungal HR. The amount of redistributed water was similar to capillary transport in the sterile sandy soil. Despite greater potential for HR, only slightly increased C mineralization and enzyme activity in the dry soil within 7 days. translocated N towards the organic substrate in the dry soil and used it for hyphal growth whereas redistributed N within the mycelial network towards the wet soil. Our results suggest that fungal hyphae have the potential to overcome capillary barriers between dry and wet soil compartments via HR and that the impact of fungal HR on C mineralization and N translocation is related to the foraging strategy and the resource usage of the fungus species.
    Keywords: Saprotrophic Fungi ; Hydraulic Redistribution ; Drought ; Carbon Mineralization ; Nitrogen Translocation ; Foraging Strategy ; Agriculture ; Chemistry
    ISSN: 0038-0717
    E-ISSN: 1879-3428
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  • 8
    Language: English
    In: Soil Biology and Biochemistry, December 2016, Vol.103, pp.349-364
    Description: The mechanistic integration of microbial behavior remains a major challenge in biogeochemical modeling of organic matter turnover in soil. We recently introduced dynamic feedbacks between specific microbial groups and their micro-environment in a biogeochemical model (Pagel et al., 2014). Here, the model was applied in a case study to simulate pesticide degradation coupled to carbon (C) turnover in the detritusphere. We aimed at unravelling the effects of litter-derived substrate supply on the spatiotemporal dynamics of the microbial community and the resulting biogeochemical processes at the mm-scale in soil. We linked genetic information on abundances of bacteria, fungi and specific pesticide degraders to the biogeochemical dynamics of C and a generic model compound (MCPA, 4-chloro-2-methylphenoxyacetic acid) in soil by multiobjective calibration. We observed and simulated increased dissolved organic and microbial C as well as accelerated MCPA degradation in soil up to a 6 mm distance to litter. We found that, whereas transport and sorption processes act as extrinsic control on the encounter of microorganisms and substrates, microbial traits such as substrate preference or metabolic capabilities intrinsically determine turnover rates triggering feedback effects on physicochemical processes such as diffusion. A process analysis revealed that C cycling and pesticide degradation in the detritusphere were strongly controlled by fungal dynamics. Our study demonstrates that integrating mathematical modeling with experiments provides comprehensive insight into the microbial regulation of matter cycling in soil.
    Keywords: Functional Trait ; Soil-Litter Interface ; Priming Effect ; Carbon Isotopes ; Functional Gene Tfda ; Pareto Analysis ; Agriculture ; Chemistry
    ISSN: 0038-0717
    E-ISSN: 1879-3428
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  • 9
    Language: English
    In: Agriculture, ecosystems & environment, 2013, Vol.165, pp.88-97
    Description: Modifications in temperature and precipitation due to climate change will likely affect carbon cycling and soil respiration in terrestrial ecosystems. Despite the important feedback mechanism of ecosystems to climate change, there is still a lack of experimental observation in agricultural ecosystems. In July 2008, we established the Hohenheim Climate Change (HoCC) experiment to investigate effects of elevated temperature and altered precipitation on soil respiration in an arable soil (mean annual temperature and precipitation 8.7°C and 679mm, respectively). We elevated soil temperature to 4cm depth by 2.5°C, reduced the amount of summer precipitation by 25%, and extended dry intervals between precipitation events. For two years, CO₂ fluxes were measured weekly and aboveground plant biomass and soil microbial biomass was determined. The results of the two-year study underline the importance of soil moisture as a driving factor in ecosystem response to climate change. Soil warming did not increase soil respiration in the first year; in the second year, a 27% increase was measured. The differential response of soil respiration to warming was most likely driven by soil moisture. In summer 2009, water limitation reduced microbial biomass in the heated plots thereby suppressing the stimulatory effect of elevated temperature on soil microorganisms. In summer 2010, the reduction in soil moisture was less pronounced and microbial biomass and respiration were not affected by water limitation. Temperature elevation significantly reduced Q₁₀ values of soil respiration by 0.7–0.8. Altered precipitation showed only minor effects during the first two years of the experiment. We conclude from our study that the moisture regime of soils under elevation of temperature will largely determine whether different soils will serve either as carbon sources or as carbon sinks. ; p. 88-97.
    Keywords: Agroecosystems ; Ecosystem Respiration ; Atmospheric Precipitation ; Microbial Biomass ; Climate Change ; Soil Water ; Biogeochemical Cycles ; Soil Respiration ; Soil Temperature ; Soil Microorganisms ; Carbon Sinks ; Soil Water Regimes ; Summer ; Soil Heating ; Arable Soils ; Aboveground Biomass
    ISSN: 0167-8809
    Source: AGRIS (Food and Agriculture Organization of the United Nations)
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  • 10
    Language: English
    In: Agriculture, Ecosystems and Environment, 15 January 2013, Vol.165, pp.88-97
    Description: ► We present one of the first climate change experiments in an agricultural ecosystem. ► The HoCC experiment combines soil warming and altered precipitation. ► Water limitation reduced microbial biomass and soil respiration in the first summer. ► Soil warming increased soil respiration in the second year by 27%. ► Moisture regime of soils largely determines their function as C sources or C sinks. Modifications in temperature and precipitation due to climate change will likely affect carbon cycling and soil respiration in terrestrial ecosystems. Despite the important feedback mechanism of ecosystems to climate change, there is still a lack of experimental observation in agricultural ecosystems. In July 2008, we established the Hohenheim Climate Change (HoCC) experiment to investigate effects of elevated temperature and altered precipitation on soil respiration in an arable soil (mean annual temperature and precipitation 8.7 °C and 679 mm, respectively). We elevated soil temperature to 4 cm depth by 2.5 °C, reduced the amount of summer precipitation by 25%, and extended dry intervals between precipitation events. For two years, CO fluxes were measured weekly and aboveground plant biomass and soil microbial biomass was determined. The results of the two-year study underline the importance of soil moisture as a driving factor in ecosystem response to climate change. Soil warming did not increase soil respiration in the first year; in the second year, a 27% increase was measured. The differential response of soil respiration to warming was most likely driven by soil moisture. In summer 2009, water limitation reduced microbial biomass in the heated plots thereby suppressing the stimulatory effect of elevated temperature on soil microorganisms. In summer 2010, the reduction in soil moisture was less pronounced and microbial biomass and respiration were not affected by water limitation. Temperature elevation significantly reduced values of soil respiration by 0.7–0.8. Altered precipitation showed only minor effects during the first two years of the experiment. We conclude from our study that the moisture regime of soils under elevation of temperature will largely determine whether different soils will serve either as carbon sources or as carbon sinks.
    Keywords: Climate Change ; Soil Warming ; Precipitation ; Soil Moisture ; Soil Respiration ; Arable Soil ; Agriculture ; Environmental Sciences
    ISSN: 0167-8809
    E-ISSN: 1873-2305
    Source: ScienceDirect Journals (Elsevier)
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