Reconstruction of Indian Ocean summer monsoon dynamicsat Nam Co using lipid biomarkers since 24 cal ka BP

Abstract HKT-ISTP 2013 B

Rhizosphere bacterial carbon turnover is higher in nucleic acids than membrane lipids : Implications for understanding soil carbon cycling

Acknowledgments We thank Agnes Fastnacht, Karl Kuebler, Steffen Ruehlow, Iris Kuhlmann, Heike Geilmann, Petra Linke, and Willi Brand for technical support in establishing the experimental setup and/or with stable isotope analyses. We also thank Bernhard Ahrens and Daniel Read for helpful discussions. This project was funded by the Max-Planck-Gesellschaft. We acknowledge Deutsche Forschungsgemeinschaft (DFG) for the fellowship to AAM in the research training group 1257 ‘Alteration and element mobility at microbe-mineral interface’ that is part of the Jena School for Microbial Communication (JSMC). AAM was also supported by the International Max Planck Research School for Global Biogeochemical Cycles (IMPRS-gBGC).Peer reviewedPublisher PD

Three dimensional photograph of single electron tracks through a scintillator

The reconstruction of particle trajectories makes it possible to distinguish between different types of charged particles. In high-energy physics, where trajectories are rather long, large size trackers must be used to achieve sufficient position resolution. However, in low-background experiments tracks are rather short and three dimensional trajectories could only be resolved in time-projection chambers so far. For detectors of large volume and therefore large drift distances, which are inevitable for low-background experiments, this technique is limited by diffusion of charge carriers. In this work we present a "proof-of-principle" experiment for a new method for the three dimensional tracking of charged particles by scintillation light: We used a setup consisting of a scintillator, mirrors, lenses and a novel imaging device (the hybrid photo detector) in order to image two projections of electron tracks through the scintillator. We took data at the T-24 beam-line at DESY with relativistic electrons with a kinetic energy of 5 GeV and from this data successfully reconstructed their three dimensional propagetion path in the scintillator. With our setup we achieved a position resolution of about 28 mum in the best case.Comment: 9 pages, 13 figures, 1 tabl

Changes in SOM under short-rotation forestry with fast-growing tree species

Soil carbon storage is strongly affected by land use and land use change. Afforestation with fast growing tree species on former arable soils may increase soil organic carbon (SOC) contents due to the reduction in soil cultivation frequency. The DFG-funded project „The mycorrhiza-mediated pathway for soil organic matter (SOM) formation and consequences for the SOM turnover under short rotation forestry“ investigates two major types of mycorrhiza formation as a function of land use and the importance of composition, stability and storage of SOM. In our subproject we compared SOC stocks of ongoing short rotation forestry (SRF) and former forestry fields (f-SRF). This leads to the following questions: i) Is there a long-term increase in carbon storage under current SRF schemes; and ii) Is this carbon storage under SRF sustainable; what are the consequences of transforming forest soils back into arable land? Two current (SRF) and two former (f-SRF) (Populus nigra x P. maximowiczii) test sites in different temporal stages of change were selected, with corresponding reference sites (REF)in each case. We found an accumulation of SOC in topsoil of current long-term SRF in comparison to REF, but lower carbon content in the subsoil. In former SRF sites accumulation of SOC was not detectable and we found no increase in the total SOC stocks per site. Effects are marked by soil treatment. Variance in total accumulation of SOC occurs in spatial distribution of investigated areas and was effected by its annual variabilities. Combined, the investigations results in following: i) SRF changes the carbon distribution in the anthric horizon. However, a total carbon storage change could not be detected. ii) The differences in carbon distribution were quickly removed by planting

Grasshopper herbivory immediately affects element cycling but not export rates in an N‐limited grassland system

As a cause of ecosystem disturbances, phytophagous insects are known to directly influence the element and organic matter (OM) cycling in ecosystems by their defoliation and excretion activity. This study focuses on the interplay between short-term, insect herbivory, plant responses to feeding activity, rhizosphere processes, and belowground nutrient availability under nutrient-poor soil conditions. To test the effects of insect herbivory on OM and nutrient cycling in an N-limited pasture system, mesocosm laboratory experiments were conducted using Dactylis glomerata as common grass species and Chorthippus dorsatus, a widespread grasshopper species, to induce strong defoliating herbivory. 13CO2 pulse labeling was used together with labeled 15N feces to trace the fate of C in soil respiration at the beginning of herbivory, and of C and N in above- and belowground plant biomass, grasshopper, feces, bulk soil, soil microbial biomass, throughfall solutions, and soil solutions. Within five days, herbivory caused a reduction in aboveground grass biomass by about 34%. A linear mixed-effects model revealed that herbivory significantly increased total dissolved C and N amounts in throughfall solutions by a factor of 4–10 (P < 0.05) compared with the control. In total, 27.6% of the initially applied feces 15N were translocated from the aboveground to the belowground system. A significant enrichment of 15N in roots led to the assumption that feces-derived 15N was rapidly taken up to compensate for the frass-related foliar N losses in light of N shortage. Soil microorganisms incorporated newly available 13C; however, the total amount of soil microbial biomass remained unaffected, while the exploitative grass species rapidly sequestered resources to facilitate its regrowth after herbivory attack. Heavy herbivory by insects infesting D. glomerata-dominated, N-deficient grasslands remarkably impacted belowground nutrient cycling by an instant amplification of available nutrients, which led to an intensified nutrient competition between plants and soil microorganisms. Consequently, these competitive plant–soil microbe interactions accelerated N cycling and effectively retained herbivory-mediated C and N surplus release resulting in diminished N losses from the system. The study highlighted the overarching role of plant adaptations to in situ soil fertility in short-term ecosystem disturbances

Detection of non-classical space-time correlations with a novel type of single-photon camera

During the last decades, multi-pixel detectors have been developed capable of registering single photons. The newly developed Hybrid Photon Detector camera has a remarkable property that it has not only spatial but also temporal resolution. In this work, we use this device for the detection of non-classical light from spontaneous parametric down-conversion and use two-photon correlations for the absolute calibration of its quantum efficiency

Increased soil carbon storage through plant diversity strengthens with time and extends into the subsoil

Soils are important for ecosystem functioning and service provisioning. Soil communities and their functions, in turn, are strongly promoted by plant diversity, and such positive effects strengthen with time. However, plant diversity effects on soil organic matter have mostly been investigated in the topsoil, and there are only very few long-term studies. Thus, it remains unclear if plant diversity effects strengthen with time and to which depth these effects extend. Here, we repeatedly sampled soil to 1 m depth in a long-term grassland biodiversity experiment. We investigated how plant diversity impacted soil organic carbon and nitrogen concentrations and stocks and their stable isotopes 13C and 15N, as well as how these effects changed after 5, 10, and 14 years. We found that higher plant diversity increased carbon and nitrogen storage in the topsoil since the establishment of the experiment. Stable isotopes revealed that these increases were associated with new plant-derived inputs, resulting in less processed and less decomposed soil organic matter. In subsoils, mainly the presence of specific plant functional groups drove organic matter dynamics. For example, the presence of deep-rooting tall herbs decreased carbon concentrations, most probably through stimulating soil organic matter decomposition. Moreover, plant diversity effects on soil organic matter became stronger in topsoil over time and reached subsoil layers, while the effects of specific plant functional groups in subsoil progressively diminished over time. Our results indicate that after changing the soil system the pathways of organic matter transfer to the subsoil need time to establish. In our grassland system, organic matter storage in subsoils was driven by the redistribution of already stored soil organic matter from the topsoil to deeper soil layers, for example, via bioturbation or dissolved organic matter. Therefore, managing plant diversity may, thus, have significant implications for subsoil carbon storage and other critical ecosystem services

Plants with arbuscular mycorrhizal fungi efficiently acquire Nitrogen from substrate additions by shaping the decomposer community composition and their net plant carbon demand

Acknowledgements SC received funding from long term DAAD scholarship to carry out the research. ML is funded by the German Research Foundation (DFG; FOR 456, FOR 1451 – “The Jena Experiment”) and by the “Zwillenberg-Tietz Stiftung”. We acknowledge help from Agnes Fastnacht with greenhouse resources and monitoring of the experiment. Special thanks to Karl Kübler for construction and deployment of the pulse labelling setup in the greenhouse. We acknowledge Heike Geilmann and Steffen Ruehlow for help with stable isotope measurements, and Maria Foerster for helping with fatty acid analysis. We also thank Erika Kothe, Ruchira Mukherji, Elisa Catao and Huei Ying Gan for helpful comments and discussions and Simon Benk for proof reading the MS. Funding Open Access funding enabled and organized by Projekt DEAL.Peer reviewedPublisher PD

Drought Reduces Release of Plant Matter Into Dissolved Organic Matter Potentially Restraining Ecosystem Recovery

Future climate scenarios indicate increasing drought intensity that threatens ecosystem functioning. However, the behavior of ecosystems during intense drought, such as the 2018 drought in Northern Europe, and their respective response following rewetting is not fully understood. We investigated the effect of drought on four different vegetation types in a temperate climate by analyzing dissolved organic matter (DOM) concentration and composition present in soil leachate, and compared it to two accompanying years. DOM is known to play an important role in ecosystem recovery and holds information on matter flows between plants, soil microorganisms and soil organic matter. Knowledge about DOM opens the possibility to better disentangle the role of plants and microorganisms in ecosystem recovery. We found that the average annual DOM concentration significantly decreased during the 2018 drought year compared to the normal year. This suggests a stimulation of DOM release under normal conditions, which include a summer drought followed by a rewetting period. The rewetting period, which holds high DOM concentrations, was suppressed under more intense drought. Our detailed molecular analysis of DOM using ultrahigh resolution mass spectrometry showed that DOM present at the beginning of the rewetting period resembles plant matter, whereas in later phases the DOM molecular composition was modified by microorganisms. We observed this pattern in all four vegetation types analyzed, although vegetation types differed in DOM concentration and composition. Our results suggest that plant matter drives ecosystem recovery and that increasing drought intensity may lower the potential for ecosystem recovery