5 results on '"Marhan, Sven"'
Search Results
2. Biogeochemical cycling of phosphorus in subsoils of temperate forest ecosystems
- Author
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Rodionov, Andrei, Bauke, Sara L., von Sperber, Christian, Hoeschen, Carmen, Kandeler, Ellen, Kruse, Jens, Lewandowski, Hans, Marhan, Sven, Mueller, Carsten W., Simon, Margaux, Tamburini, Federica, Uhlig, David, von Blanckenburg, Friedhelm, Lang, Friederike, Amelung, Wulf, Soil Ecology, University of Bayreuth, Bayreuth, Germany, Institute of Crop Science and Resource Conservation (INRES) – Soil Science and Soil Ecology, University of Bonn, Bonn, Germany, Department of Geography, McGill University, Montreal, Canada, Chair of Soil Science, Department of Ecology and Ecosystem Management, Technical University of Munich, Freising-Weihenstephan, Germany, Institute of Soil Science and Land Evaluation, Soil Biology Department, University of Hohenheim, Stuttgart, Germany, Institute of Bio- and Geosciences – Agrosphere (IBG-3), Forschungszentrum Jülich GmbH, Jülich, Germany, Department of Geosciences and Natural Resource Management, Section for Geography, University of Copenhagen, Copenhagen, Denmark, Institute of Agricultural Sciences, ETH Zurich, Lindau, Switzerland, GFZ German Research Centre for Geosciences, Earth Surface Geochemistry, Potsdam, Germany, and Chair of Soil Ecology, University of Freiburg, Freiburg (i. Br.), Germany
- Subjects
Biogeochemical cycle ,chemistry.chemical_element ,Phosphate ,010501 environmental sciences ,01 natural sciences ,Soil ,Nutrient ,ddc:550 ,Environmental Chemistry ,NanoSIMS ,Oxygen isotopes ,XANES ,Microbial P cycling ,Subsoil ,0105 earth and related environmental sciences ,Earth-Surface Processes ,Water Science and Technology ,Rhizosphere ,Topsoil ,Phosphorus ,Temperate forest ,04 agricultural and veterinary sciences ,ddc ,chemistry ,Environmental chemistry ,ddc:551.9 ,Soil water ,040103 agronomy & agriculture ,0401 agriculture, forestry, and fisheries - Abstract
Tree roots penetrate the soil to several meters depth, but the role of subsoils for the supply of nutrient elements such as phosphorus (P) to the trees is poorly understood. Here, we tested the hypothesis that increased P deficiency in the topsoil results in an increased microbial recycling of P from the forest subsoil. We sampled soils from four German temperate forest sites representing a gradient in total P stocks. We analyzed the oxygen isotopic composition of HCl-extractable phosphate (δ18OP) and identified differences in P speciation with increasing soil depth using X-ray absorption near-edge structure (XANES) spectroscopy. We further determined microbial oxygen demand with and without nutrient supply at different soil depths to analyse nutrient limitation of microbial growth and used nanoscale secondary ion mass spectrometry (NanoSIMS) to visualize spatial P gradients in the rhizosphere. We found that δ18OP values in the topsoil of all sites were close to the isotopic signal imparted by biological cycling when oxygen isotopes in phosphate are exchanged by enzymatic activity. However, with increasing soil depth and increasing HCl-P concentrations, δ18Ο values continuously decreased towards values expected for primary minerals in parent material at depths below 60 cm at sites with high subsoil P stocks and below more than 2 m at sites with low subsoil P stocks, respectively. For these depths, XANES spectra also indicated the presence of apatite. NanoSIMS images showed an enrichment of P in the rhizosphere in the topsoil of a site with high P stocks, while this P enrichment was absent at a site with low P stocks and in both subsoils. Addition of C, N and P alone or in combination revealed that microbial activity in subsoils of sites with low P stocks was mostly P limited, whereas sites with high P stocks indicated N limitation or N and P co-limitation. We conclude that subsoil P resources are recycled by trees and soil microorganisms. With continued weathering of the bedrock and mobilisation of P from the weathered rocks, P cycling will proceed to greater depths, especially at sites characterised by P limitation., Biogeochemistry, 150 (3), ISSN:0168-2563, ISSN:1573-515X
- Published
- 2019
3. Abundance and activity of nitrate reducers in an arable soil are more affected by temporal variation and soil depth than by elevated atmospheric [CO2]
- Author
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Marhan, Sven, Philippot, Laurent, Bru, David, Rudolph, Sabine, Franzaring, Jürgen, Högy, Petra, Fangmeier, Andreas, Kandeler, Ellen, Institute of Soil Science and Land Evaluation, Soil Biology Section, University of Hohenheim, Microbiologie, Institut National de la Recherche Agronomique (INRA)-Université de Bourgogne (UB), and Institute for Landscape and Plant Ecology
- Subjects
DNA, Bacterial ,Nitrates ,functional genes ,nitrate reductase ,Bacteria ,Brassica napus ,Agriculture ,Carbon Dioxide ,Carbon ,Quaternary Ammonium Compounds ,Soil ,[SDV.MP]Life Sciences [q-bio]/Microbiology and Parasitology ,Biodegradation, Environmental ,Bacterial Proteins ,Nitrate Reductases ,nitrogen cycle ,Seasons ,elevation of CO2 ,Ecosystem ,Soil Microbiology - Abstract
International audience; Elevated atmospheric carbon dioxide concentrations ([CO2]) might change the abundance and the function of soil microorganisms in the depth profile of agricultural soils by plant-mediated reactions. The seasonal pattern of abundance and activity of nitrate-reducing bacteria was studied in a Mini-FACE experiment planted with oilseed rape (Brassica napus). Three depths (0–10, 10–20 and 20–30 cm) were sampled. Analyses of the abundances of total (16S rRNA gene) and nitrate-reducing bacteria (narG, napA) revealed strong influences of sampling date and depth, but no [CO2] effects. Abundance and activity of nitrate reducers were higher in the top soil layer and decreased with depth but were not related to extractable amounts of nitrogen and carbon in soil. Dry periods reduced abundances of total and nitrate-reducing bacteria, whereas the potential activity of the nitrate reductase enzyme was not affected. Enzyme activity was only weakly correlated to the abundance of nitrate-reducing bacteria but was related to NH4+ and NO3− concentrations. Our results suggest that in contrast to the observed pronounced seasonal changes, the elevation of atmospheric [CO2] has only a marginal impact on nitrate reducers in the investigated arable ecosystem.
- Published
- 2011
4. Interactions between cover crops and soil microorganisms increase phosphorus availability in conservation agriculture
- Author
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Hallama, Moritz, Pekrun, Carola, Pilz, Stefan, Jarosch, Klaus A., Frąc, Magdalena, Uksa, Marie, Marhan, Sven, and Kandeler, Ellen
- Subjects
2. Zero hunger ,13. Climate action ,fungi ,550 Earth sciences & geology ,food and beverages ,15. Life on land - Abstract
Aims An essential task of agricultural systems is to im- prove internal phosphorus (P) recycling. Cover crops and tillage reduction can increase sustainability, but it is not known whether stimulation of the soil microbial commu- nity can increase the availability of soil organic P pools. Methods In a field experiment in southwest Germany, the effects of a winter cover crop mixture (vs. bare fallow) and no-till (vs. non-inversion tillage) on microbial P- cycling were assessed with soybean as the main crop. Microbial biomass, phospholipid fatty acids (PLFAs), P cycling enzymes, and carbon-substrate use capacity were linked for the first time with the lability of organic P pools measured by enzyme addition assays (using phosphodi- esterase, non-phytase-phosphomonoesterase and fungal phytase). Results Microbial phosphorus, phosphatase, and fatty acids increased under cover crops, indicating an en- hanced potential for organic P cycling. Enzyme-stable organic P shifted towards enzyme-labile organic P pools. Effects of no-till were weaker, and a synergy with cover crops was not evident. Conclusions In this experiment, cover crops were able to increase the microbially mediated internal P cycling in a non-P-limited, temperate agroecosystems.
5. Land-use intensity and biodiversity effects on infiltration capacity and hydraulic conductivity of grassland soils in southern Germany
- Author
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Leimer, Sophia, Berner, Doreen, Birkhofer, Klaus, Boeddinghaus, Runa S., Fischer, Markus, Kandeler, Ellen, Kuka, Katrin, Marhan, Sven, Prati, Daniel, Schäfer, Deborah, Schoning, Ingo, Solly, Emily F., Wolters, Volkmar, and Wilcke, Wolfgang
- Subjects
13. Climate action ,15. Life on land ,580 Plants (Botany) ,6. Clean water - Abstract
Evidence from experimental and established grasslands indicates that plant biodiversity can modify the water cycle. One suspected mechanism behind this is a higher infiltration capacity (nu(B)) and hydraulic conductivity (K) of the soil on species-rich grasslands. However, in established and agriculturally managed grasslands, biodiversity effects cannot be studied independent of land-use effects. Therefore, we investigated in established grassland systems how land-use intensity and associated biodiversity of plants and soil animals affect nu(B) and K at and close to saturation. On 50 grassland plots along a land-use intensity gradient in the Biodiversity Exploratory Schwabische Alb, Germany, we measured nu(B) with a hood infiltrometer at several matrix potentials and calculated the saturated and unsaturated K. We statistically analysed the relationship between nu(B) or K and land-use information (e.g., fertilising intensity), abiotic (e.g., soil texture) and biotic data (e.g., plant species richness, earthworm abundance). Land-use intensity decreased and plant species richness increased nu(B) and K, while the direction of the effects of soil animals was inconsistent. The effect of land-use intensity on nu(B) and K was mainly attributable to its negative effect on plant species richness. Our results demonstrate that plant species richness was a better predictor of nu(B) and K at and close to saturation than land-use intensity or soil physical properties in the established grassland systems of the Schwabische Alb.
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