Human actions are causing (1) declines in biodiversity, (2) increases in atmospheric CO2 and (3) increases in N deposition. The interactive effects of these factors and their consequences on ecosystem processes are unknown, though they play a critical role in global soil C storage dynamics. Recent data from well-replicated, long-term studies on the effects of plant diversity on both ecosystem productivity and carbon sequestration show that enhanced biomass accumulation is positively related to plant diversity. Moreover, preliminary work suggests that plant species composition may be as important as species diversity in affecting soil C sequestration. Finally, biotic factors such as herbivory through indirect effects on plant roots, affect long-term fate of C and below-ground processes. Hence, the present project aims to address the effects of (1) plant diversity, (2) plant community composition, (3) N deposition, and (4) herbivory on soil C storage dynamics. The study will make use of a well-replicated, long-term study design that has been established in 1994 at Cedar Creek, Minnesota, US, as well as glasshouse experiments using isotopic techniques in the UK. Soil and plant material will be measured for C and N. Data on plant productivity, N mineralization rat es, C:N ratios, and nitrogen use efficiency will be collected according to different treatments. The research project is the first, to our knowledge, to test the effects of varying biodiversity, species functional composition and N fertilization on soil C storage dynamics at the ecosystem-scale being part of a well-replicated, long-term factorial grassland biodiversity experiment. Therefore, the overall results of the study will contribute to the important ongoing scientific research, which focuses on the effects of climate change on terrestrial ecosystems, with a particular bias towards those mechanisms involved in the global C storage dynamics.
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