Gerd Gleixner

Friedrich Schiller University Jena, Jena, Thuringia, Germany

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Publications (191)500.27 Total impact

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    ABSTRACT: Using a pulse chase 13 CO 2 plant labeling experiment we compared the flow of plant carbon into macromolecular fractions of rhizosphere soil microorganisms. Time dependent 13 C dilution patterns in microbial cellular fractions were used to calculate their turnover time. The turnover times of microbial biomolecules were found to vary: microbial RNA (19 h) and DNA (30 h) turned over fastest followed by chloroform fumigation extraction-derived soluble cell lysis products (14 days), while phospholipid fatty acids (PLFAs) had the slowest turnover (42 days). PLFA/NLFA 13 C analyses suggest that both mutualistic arbuscular mycorrhizal and saprophytic fungi are dominant in initial plant carbon uptake. In contrast, high initial 13 C enrichment in RNA hints at bacterial importance in initial C uptake due to the dominance of bacterial derived RNA in total extracts of soil RNA. To explain this discrepancy, we observed low renewal rate of bacterial lipids, which may therefore bias lipid fatty acid based interpretations of the role of bacteria in soil microbial food webs. Based on our findings, we question current assumptions regarding plant-microbe carbon flux and suggest that the rhizosphere bacterial contribution to plant assimilate uptake could be higher. This highlights the need for more detailed quantitative investigations with nucleic acid biomarkers to further validate these findings.
    Frontiers in Microbiology 05/2015; 6(268). DOI:10.3389/fmicb.2015.00268 · 3.94 Impact Factor
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    ABSTRACT: Reduced carbon (C) assimilation during prolonged drought forces trees to rely on stored C to maintain vital processes like respiration. It has been shown, however, that the use of carbohydrates, a major C storage pool and apparently the main respiratory substrate in plants, strongly declines with decreasing plant hydration. Yet no empirical evidence has been produced to what degree other C storage compounds like lipids and proteins may fuel respiration during drought. We exposed young scots pine trees to C limitation using either drought or shading and assessed respiratory substrate use by monitoring the respiratory quotient, δ(13) C of respired CO2 and concentrations of the major storage compounds, that is, carbohydrates, lipids and amino acids. Only shaded trees shifted from carbohydrate-dominated to lipid-dominated respiration and showed progressive carbohydrate depletion. In drought trees, the fraction of carbohydrates used in respiration did not decline but respiration rates were strongly reduced. The lower consumption and potentially allocation from other organs may have caused initial carbohydrate content to remain constant during the experiment. Our results suggest that respiratory substrates other than carbohydrates are used under carbohydrate limitation but not during drought. Thus, respiratory substrate shift cannot provide an efficient means to counterbalance C limitation under natural drought. © 2015 The Authors New Phytologist © 2015 New Phytologist Trust.
    New Phytologist 05/2015; DOI:10.1111/nph.13452 · 6.55 Impact Factor
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    ABSTRACT: We analyzed refractory black carbon (rBC) in an ice core spanning 1875-2000 AD from Mt. Muztagh Ata, the Eastern Pamirs, using a Single Particle Soot Photometer (SP2). Additionally a pre-existing levoglucosan record from the same ice core was used to differentiate rBC that originated from open fires, energy-related combustion of biomass, and fossil fuel combustion. Mean rBC concentrations increased four-fold since the mid-1970s and reached maximum values at the end of 1980s. The observed decrease of the rBC concentrations during the 1990s was likely driven by the economic recession of former USSR countries in Central Asia. Levoglucosan concentrations showed a similar temporal trend to rBC concentrations, exhibiting a large increase around 1980 AD followed by a decrease in the 1990s that was likely due to a decrease in energy-related biomass combustion. The time evolution of levoglucosan/rBC ratios indicated stronger emissions from open fires during the 1940s-1950s, while the increase in rBC during the 1980s-1990s was caused from an increase in energy-related combustion of biomass and fossil fuels.
    Atmospheric Environment 05/2015; 115. DOI:10.1016/j.atmosenv.2015.05.034 · 3.06 Impact Factor
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    ABSTRACT: Soil moisture is the dynamic link between climate, soil and vegetation and the dynamics and variation are affected by several often interrelated factors such as soil texture, soil structural parameters (soil organic carbon) and vegetation parameters (belowground-and aboveground biomass). For the characterization and estimation of soil moisture and its variability and the resulting water fluxes and solute transports, the knowledge of the relative importance of these factors is of major challenge for hydrology and bioclimatology. Because of the heterogeneity of these factors, soil moisture varies strongly over time and space. Our objective was to assess the spatio-temporal variability of soil moisture and factors which could explain that variability, like soil properties and vegetation cover, in in a long term biodiversity experiment (Jena Experiment). The Jena Experiment consist 86 plots on which plant species richness (0, 1, 2, 4, 8, 16, and 60) and functional groups (legumes, grasses, tall herbs, and small herbs) were manipulated in a factorial design Soil moisture measurements were performed weekly April to September 2003-2005 and 2008-2013 using Delta T theta probe. Measurements were integrated to three depth intervals: 0.0 – 0.20, 0.20 – 0.40 and 0.40 – 0.70 m. We analyze the spatio-temporal patterns of soil water content on (i) the normalized time series and (ii) the first components obtained from a principal component analysis (PCA). Both were correlated with the design variables of the Jena Experiment (plant species richness and plant functional groups) and other influencing factors such as soil texture, soil structural variables and vegetation parameters. For the time stability of soil water content, the analysis showed that plots containing grasses was consistently drier than average at the soil surface in all observed years while plots containing legumes comparatively moister, but only up to the year 2008. In 0.40 – 0.70 m soil deep plots presence of small herbs led to higher than average soil moisture in some years (2008, 2012, 2013). Interestingly, plant species richness led to moister than average subsoil at the beginning of the experiment (2003 and 2004), which changed to lower than average up to the year 2010 in all depths. There was no effect of species diversity in the years since 2010, although species diversity generally increases leaf area index and aboveground biomass. The first component from the PCA analysis described the mean behavior in time of all soil moisture time series. The second component reflected the impact of soil depth. The first two components explained 76% of the data set total variance. The third component is linked to plant species richness and explained about 4 % of the total variance of soil moisture data. The fourth component, which explained 2.4 %, showed a high correlation to soil texture.
    EGU, Vienna; 04/2015
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    ABSTRACT: Plant diversity strongly influences ecosystem functions and services, such as soil carbon storage. However, the mechanisms underlying the positive plant diversity effects on soil carbon storage are poorly understood. We explored this relationship using long-term data from a grassland biodiversity experiment (The Jena Experiment) and radiocarbon (14C) modelling. Here we show that higher plant diversity increases rhizosphere carbon inputs into the microbial community resulting in both increased microbial activity and carbon storage. Increases in soil carbon were related to the enhanced accumulation of recently fixed carbon in high-diversity plots, while plant diversity had less pronounced effects on the decomposition rate of existing carbon. The present study shows that elevated carbon storage at high plant diversity is a direct function of the soil microbial community, indicating that the increase in carbon storage is mainly limited by the integration of new carbon into soil and less by the decomposition of existing soil carbon.
    Nature Communications 04/2015; 6. DOI:10.1038/ncomms7707 · 10.74 Impact Factor
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    ABSTRACT: We examined the molecular composition of forest soil water during three different seasons at three different sites, using electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI-FT-ICR-MS). We examined oxic soils and tested the hypothesis that pH and season correlate with the molecular composition of dissolved organic matter (DOM). We used molecular formulae and their relative intensity from ESI-FT-ICR-MS for statistical analysis. Applying unconstrained and constrained ordination methods, we observed that pH, dissolved organic carbon (DOC) concentration and season were the main factors correlating with DOM molecular composition. This result is consistent with a previous study where pH was a main driver of the molecular differences between DOM from oxic rivers and anoxic bog systems in the Yenisei River catchment. At a higher pH, the molecular formulae had a lower degree of unsaturation and oxygenation, lower molecular size and a higher abundance of nitrogen-containing compounds. These characteristics suggest a higher abundance of tannin connected to lower pH that possibly inhibited biological decomposition. Higher biological activity at a higher pH might also be related to the higher abundance of nitrogen-containing compounds. Comparing the seasons, we observed a decrease in unsaturation, molecular diversity and the number of nitrogen-containing compounds in the course of the year from March to November. Temperature possibly inhibited biological degradation during winter, which could cause the accumulation of a more diverse compound spectrum until the temperature increased again. Our findings suggest that the molecular composition of DOM in soil pore waters is dynamic and a function of ecosystem activity, pH and temperature.
    PLoS ONE 03/2015; 10(3):e0119188. DOI:10.1371/journal.pone.0119188 · 3.53 Impact Factor
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    ABSTRACT: The transition from the Last Glacial to the current Interglacial, the Holocene, represents an important period with climatic and environmental changes impacting ecosystems. In this study, we examined the interplay between the Indian Ocean Summer Monsoon (IOSM) and the Westerlies at lake Nam Co, southern Tibet to understand the climatic effects on the ecosystem. Different organic geochemical proxies (n-alkanes, glycerol dialkyl glycerol tetraethers, δD, δ13Corg, δ15N) are applied to reconstruct the environmental and hydrological changes on one of the longest available paleorecords at the Tibetan Plateau. Based on our paleohydrological δD proxies, the aquatic signal lags the terrestrial one due to specific ecological thresholds, which, in addition to climatic changes, can influence aquatic organisms. The aquatic organisms' response strongly depends on temperature and associated lake size, as well as pH and nutrient availability. Because the terrestrial vegetation reacts faster and more sensitively to changes in the monsoonal and climatic system, the δD of n-C29 and the reconstructed inflow water signal represent an appropriate IOSM proxy. In general, the interplay of the different air masses seems to be primarily controlled by solar insolation. In the Holocene, the high insolation generates a large land-ocean pressure gradient associated with strong monsoonal winds and the strongest IOSM. In the Last Glacial period, however, the weak insolation promoted the Westerlies, thereby increasing their influence at the Tibetan Plateau. Our results help to elucidate the variable IOSM, and they illustrate a remarkable shift in the lake system regarding pH, δ13Corg and δ15N from the Last Glacial to the Holocene interglacial period.
    Quaternary Science Reviews 03/2015; 112. DOI:10.1016/j.quascirev.2015.01.023 · 4.57 Impact Factor
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    Isotopes in Environmental and Health Studies 03/2015; 51(1):1-6. DOI:10.1080/10256016.2015.1016022 · 1.29 Impact Factor
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    ABSTRACT: We investigated how the carbon quality of soil amendments based upon their carbon (C)-to-nitrogen (N) -ratio and their degree of aromaticity influence soil N transformations and affect N partitioning between soils, plants and microorganisms. A better understanding of these interactions might offer the possibility to optimize N use efficiency in agriculture. We performed a randomized pot experiment with winter wheat and compared the influence of naturally 13C labelled soil additives in three increasing condensation degrees, i.e. corn silage, hydrochar and pyrochar, in combination with three levels of 15N labelled NO3− on plant growth and N allocation. Corn silage, a lignocellulose material with a wide C-to-N-ratio and low condensation degree, which was also used as starting material for the two other amendments, favoured microbial growth and activity while simultaneously leading to N deficiency in wheat plants. In contrast, hydrochar and pyrochar positively influenced plant growth independent of their C-to-N-ratio and their degree of aromaticity. After adding hydrochar, plants did not take up the added fertilizer N but obviously used NH4+ from mineralized hydrochar to meet their N demands. After adding pyrochar, fertilizer NO3− was used effectively by plants and fertilizer levels were still visible in the soil, while microbial activity was low. Our results clearly demonstrate that C quality strongly affects the N partitioning in the plant–soil–microorganism system. Hydrochars with a low degree of condensation that are slowly degraded by soil microorganisms might substitute N fertilizers whereas highly condensed pyrochars decreasing the soil microbial activity might enhance the N use efficiency of plants.
    Soil Biology and Biochemistry 02/2015; 81. DOI:10.1016/j.soilbio.2014.11.024 · 4.41 Impact Factor
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    ABSTRACT: This study investigated the possible effects of tree species diversity and identity on the soil microbial community in a species-rich temperate broad-leaved forest. For the first time, we separated the effects of tree identity and tree species diversity on the link between above and belowground communities in a near-natural forest. We established 100 tree clusters consisting of each three tree individuals represented by beech (Fagus sylvatica L.), ash (Fraxinus excelsior L.), hornbeam (Carpinus betulus L.), maple (Acer pseudoplatanus L.), or lime (Tilia spec.) at two different sites in the Hainich National Park (Thuringia, Germany). The tree clusters included one, two or three species forming a diversity gradient. We investigated the microbial community structure, using phospholipid fatty acid (PLFA) profiles, in mineral soil samples (0–10 cm) collected in the centre of each cluster.
    Soil Biology and Biochemistry 02/2015; 81. DOI:10.1016/j.soilbio.2014.11.020 · 4.41 Impact Factor
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    ABSTRACT: Background and aims Soil hydraulic properties drive water distribution and availability in soil. There exists limited knowledge of how plant species diversity might influence soil hydraulic properties. Methods We quantified the change in infiltration capacity affected by soil structural variables (soil bulk density, porosity and organic carbon content) along a gradient of soil texture, plant species richness (1, 2, 4, 8, 16 and 60)and functional group composition (grasses, legumes, small herbs, tall herbs). We conducted two infiltration measurement campaigns (May and October 2012) using a hood infiltrometer. Results Plant species richness significantly increased infiltration capacity in the studied grasslands. Both soil porosity (or inversely bulk density) and organic carbon played an important role in mediating the plant species richness effect. Soil texture did not correlate with infiltration capacity. In spring 2012, earthworm biomass increased infiltration capacity, but this effect could not be attributed to changes in soil structural variables. Conclusions We experimentally identified important ecological drivers of infiltration capacity, suggesting complex interactions between plant species richness, earthworms, and soil structural variables, while showing little impact of soil texture. Changes in plant species richness may thus have significant effects on soil hydraulic properties with potential consequences for surface run-off and soil erosion.
    Plant and Soil 01/2015; DOI:10.1007/s11104-014-2373-5 · 3.24 Impact Factor
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    Andrea Scheibe, Gerd Gleixner
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    ABSTRACT: We investigated the effect of leaf litter on below ground carbon export and soil carbon formation in order to understand how litter diversity affects carbon cycling in forest ecosystems. 13C labeled and unlabeled leaf litter of beech (Fagus sylvatica) and ash (Fraxinus excelsior), characterized by low and high decomposability, were used in a litter exchange experiment in the Hainich National Park (Thuringia, Germany). Litter was added in pure and mixed treatments with either beech or ash labeled with 13C. We collected soil water in 5 cm mineral soil depth below each treatment biweekly and determined dissolved organic carbon (DOC), δ13C values and anion contents. In addition, we measured carbon concentrations and δ13C values in the organic and mineral soil (collected in 1 cm increments) up to 5 cm soil depth at the end of the experiment. Litter-derived C contributes less than 1% to dissolved organic matter (DOM) collected in 5 cm mineral soil depth. Better decomposable ash litter released significantly more (0.50±0.17%) litter carbon than beech litter (0.17±0.07%). All soil layers held in total around 30% of litter-derived carbon, indicating the large retention potential of litter-derived C in the top soil. Interestingly, in mixed (ash and beech litter) treatments we did not find a higher contribution of better decomposable ash-derived carbon in DOM, O horizon or mineral soil. This suggest that the known selective decomposition of better decomposable litter by soil fauna has no or only minor effects on the release and formation of litter-derived DOM and soil organic matter. Overall our experiment showed that 1) litter-derived carbon is of low importance for dissolved organic carbon release and 2) litter of higher decomposability is faster decomposed, but litter diversity does not influence the carbon flow.
    PLoS ONE 12/2014; 9(12):e114040. DOI:10.1371/journal.pone.0114040 · 3.53 Impact Factor
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    Biology and Fertility of Soils 12/2014; DOI:10.1007/s00374-014-0980-1 · 3.40 Impact Factor
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    ABSTRACT: Trees and shrubs in tropical Africa use the C3 cycle as a carbon fixation pathway during photosynthesis, while grasses and sedges mostly use the C4 cycle. Leaf-wax lipids from sedimentary archives such as the long-chain n -alkanes (e.g., n -C27 to n -C33) inherit carbon isotope ratios that are representative of the carbon fixation pathway. Therefore, n -alkane δ 13C values are often used to reconstruct past C3/C4 composition of vegetation, assuming that the relative proportions of C3 and C4 leaf waxes reflect the relative proportions of C3 and C4 plants. We have compared the δ 13C values of n -alkanes from modern C3 and C4 plants with previously published values from recent lake sediments and provide a framework for estimating the fractional contribution (areal-based) of C3 vegetation cover (fC3fC3) represented by these sedimentary archives. Samples were collected in Cameroon, across a latitudinal transect that accommodates a wide range of climate zones and vegetation types, as reflected in the progressive northward replacement of C3-dominated rain forest by C4-dominated savanna. The C3 plants analysed were characterised by substantially higher abundances of n -C29 alkanes and by substantially lower abundances of n -C33 alkanes than the C4 plants. Furthermore, the sedimentary δ 13C values of n -C29 and n -C31 alkanes from recent lake sediments in Cameroon (−37.4‰ to −26.5‰) were generally within the range of δ 13C values for C3 plants, even when from sites where C4 plants dominated the catchment vegetation. In such cases simple linear mixing models fail to accurately reconstruct the relative proportions of C3 and C4 vegetation cover when using the δ 13C values of sedimentary n -alkanes, overestimating the proportion of C3 vegetation, likely as a consequence of the differences in plant wax production, preservation, transport, and/or deposition between C3 and C4 plants. We therefore tested a set of non-linear binary mixing models using δ 13C values from both C3 and C4 vegetation as end-members. The non-linear models included a sigmoid function (sine-squared) that describes small variations in the fC3fC3 values as the minimum and maximum δ13C values are approached, and a hyperbolic function that takes into account the differences between C3 and C4 plants discussed above. Model fitting and the estimation of uncertainties were completed using the Monte Carlo algorithm and can be improved by future data addition. Models that provided the best fit with the observed δ13C values of sedimentary n-alkanes were either hyperbolic functions or a combination of hyperbolic and sine-squared functions. Such non-linear models may be used to convert δ13C measurements on sedimentary n-alkanes directly into reconstructions of C3 vegetation cover.
    Geochimica et Cosmochimica Acta 10/2014; 142:482–500. DOI:10.1016/j.gca.2014.07.004 · 4.25 Impact Factor
  • ORCHEM 2014, Weimar; 09/2014
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    ABSTRACT: In general, a moderate drying trend is observed in mid-latitude arid Central Asia since the Mid-Holocene, attributed to the progressively weakening influence of the mid-latitude Westerlies on regional climate. However, as the spatio-temporal pattern of this development and the underlying climatic mechanisms are yet not fully understood, new high-resolution paleoclimate records from this region are needed. Within this study, a sediment core from Lake Son Kol (Central Kyrgyzstan) was investigated using sedimentological, (bio)geochemical, isotopic, and palynological analyses, aiming at reconstructing regional climate development during the last 6000 years. Biogeochemical data, mainly reflecting summer moisture conditions, indicate predominantly wet conditions until 4950 cal. yr BP, succeeded by a pronounced dry interval between 4950 and 3900 cal. yr BP. In the following, a return to wet conditions and a subsequent moderate drying trend until present times are observed. This is consistent with other regional paleoclimate records and likely reflects the gradual Late Holocene diminishment of the amount of summer moisture provided by the mid-latitude Westerlies. However, climate impact of the Westerlies was apparently not only restricted to the summer season but also significant during winter as indicated by recurrent episodes of enhanced allochthonous input through snowmelt, occurring before 6000 cal. yr BP and at 5100–4350, 3450–2850, and 1900–1500 cal. yr BP. The distinct ~1500-year periodicity of these episodes of increased winter precipitation in Central Kyrgyzstan resembles similar cyclicities observed in paleoclimate records around the North Atlantic, likely indicating a hemispheric-scale climatic teleconnection and an impact of North Atlantic Oscillation (NAO) variability in Central Asia.
    The Holocene 07/2014; 24(8):970-984. DOI:10.1177/0959683614534741 · 3.79 Impact Factor
  • Trends in Metabolomics - Analytics and Applications, Frankfurt a.M.; 06/2014
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    ABSTRACT: Current carbon cycle-climate models predict that future soil carbon storage will be determined by the balance between CO2 fertilization and warming. However, it is uncertain whether greater carbon inputs to soils with elevated CO2 will be sequestered, particularly since warming hastens soil carbon decomposition rates, and may alter the response of soils to new plant inputs. We studied the effects of elevated CO2 and warming on microbial soil carbon decomposition processes using laboratory manipulations of carbon inputs and soil temperature. We incubated soils from the Aspen Free Air CO2 Enrichment experiment, where no accumulation of soil carbon has been observed despite a decade of increased carbon inputs to soils under elevated CO2. We added isotopically-labeled sucrose to these soils in the laboratory to mimic and trace the effects of increased carbon inputs on soil organic carbon decomposition and its temperature sensitivity. Sucrose additions caused a positive priming of soil organic carbon decomposition, demonstrated by increased respiration derived from soil carbon, increased microbial abundance, and a shift in the microbial community towards faster growing microorganisms. Similar patterns were observed for elevated CO2 soils, suggesting that the priming effect was responsible for reductions in soil carbon accumulation at the site. Laboratory warming accelerated the rate of the priming effect, but the magnitude of the priming effect was not different amongst temperatures, suggesting that the priming effect was limited by substrate availability, not soil temperature. No changes in substrate use efficiency were observed with elevated CO2 or warming. The stimulatory effects of warming on the priming effect suggest that increased belowground carbon inputs from CO2 fertilization are not likely to be stored in mineral soils.
    Soil Biology and Biochemistry 05/2014; 76. DOI:10.1016/j.soilbio.2014.04.028 · 4.41 Impact Factor
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    ABSTRACT: Plant diversity drives changes in the soil microbial community which may result in alterations in ecosystem functions. However, the governing factors between the composition of soil microbial communities and plant diversity are not well understood. We investigated the impact of plant diversity (plant species richness and functional group richness) and plant functional group identity on soil microbial biomass and soil microbial community structure in experimental grassland ecosystems. Total microbial biomass and community structure were determined by phospholipid fatty acid (PLFA) analysis. The diversity gradient covered 1, 2, 4, 8, 16 and 60 plant species and 1, 2, 3 and 4 plant functional groups (grasses, legumes, small herbs and tall herbs). In May 2007, soil samples were taken from experimental plots and from nearby fields and meadows. Beside soil texture, plant species richness was the main driver of soil microbial biomass. Structural equation modeling revealed that the positive plant diversity effect was mainly mediated by higher leaf area index resulting in higher soil moisture in the top soil layer. The fungal-to-bacterial biomass ratio was positively affected by plant functional group richness and negatively by the presence of legumes. Bacteria were more closely related to abiotic differences caused by plant diversity, while fungi were more affected by plant-derived organic matter inputs. We found diverse plant communities promoted faster transition of soil microbial communities typical for arable land towards grassland communities. Although some mechanisms underlying the plant diversity effect on soil microorganisms could be identified, future studies have to determine plant traits shaping soil microbial community structure. We suspect differences in root traits among different plant communities, such as root turnover rates and chemical composition of root exudates, to structure soil microbial communities.
    PLoS ONE 05/2014; 9(5):e96182. DOI:10.1371/journal.pone.0096182 · 3.53 Impact Factor

Publication Stats

5k Citations
500.27 Total Impact Points

Institutions

  • 2013–2015
    • Friedrich Schiller University Jena
      • • Institute of Geosciences
      • • Institut für Ökologie
      Jena, Thuringia, Germany
  • 1999–2015
    • Max Planck Institute for Biogeochemistry Jena
      • Department of Biogeochemical Processes
      Jena, Thuringia, Germany
    • University of Rostock
      • Faculty of Agricultural and Environmental Sciences
      Rostock, Mecklenburg-Vorpommern, Germany
  • 2006
    • Hohenheim University
      • Institute of Food Chemistry
      Stuttgart, Baden-Wuerttemberg, Germany
  • 2001
    • Max Planck Institute for Chemical Ecology
      Jena, Thuringia, Germany
  • 1998
    • Scottish Crop Research Institute
      Aberdeen, Scotland, United Kingdom