Soil organic matter storage as a function of plant biodiversity

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Over the last years of the Jena Experiment, we have observed a significant positive relationship between plant biodiversity and carbon storage in soils on the one hand and plant biomass production on the other hand. Most interestingly, plant biodiversity per se was more important for the observed increase in soil carbon than plant biomass inputs. The mechanisms behind this unexpected result, however, are still unclear. We therefore suggest identifying the underlying processes. At first we will compare the measured total soil carbon stock changes with newly formed soil organic matter based on 14C isotope mass balances. This approach will quantify the effect of biodiversity on the decomposition of inherited carbon older then the experiment. In a second independent approach, we will determine chemical markers of input material, stored soil carbon and exported dissolved carbon from all biodiversity levels to draw conclusions on the quality and hence the origin and turnover of stored soil carbon. In a stepwise approach of chemical methods, we will identify root related markers like lignin, cellulose or lipids and microbial markers like proteins or phospholipids and study the storage processes. Finally we will use the joint labelling experiment at the ECOTRON facility to trace the flow of labelled CO2 and NOx into soil microorganisms and soil organic matter. The use of independent labels will allow to distinct between uptake and storage related processes from decomposition processes.