Effects of Forest Biodiversity and Climate on Ecosystem Carbon Flux

One of the major questions at the interface between life and environmental sciences is how ecosystems will respond to global change in the face of continuing reductions of biodiversity. Due to their potential to store large amounts of carbon in biomass and to prevent soil erosion, forests are of particular importance but difficult to manipulate experimentally. We are using a network of forest plots in China to test (A) if short-term fluctuations in carbon and water fluxes after environmental "events" such as days with rain or hot dry weather are larger in plots with low than with higher tree species diversity and (B) how belowground plant biomass and carbon flux from soil are affected by tree species diversity.

Part A uses a novel phytometer approach and isotopic measurements of respired CO2, phloem sap, bulk or cellulose material of above and below ground plant compartments. The variation of ecophysiological variables as well as the isotopic signature caused by environmental “events” are used to measure the changes of ecosystem processes and the associated carbon allocation in the ecosystem in relation to tree species diversity. A rain exclusion treatment was added in the second year to examine if high biodiversity levels can buffer short-term variation in ecosystem processes under environmental change.

Part B, led by our Chinese collaborators, uses in-growth cores and direct coring to assess the effects of tree species diversity on belowground biomass. Furthermore, tree rings are analyzed for annual biomass increase and isotopic signature. Tree ring analysis is a good tool to understand the integrative response of plant carbon allocation to environmental variation. Using inter-annual climatic variation and its consequences for biomass production, we will test if high biodiversity levels can buffer longer-term variation in biomass under environmental change.

The Swiss and Chinese applicants and students closely collaborate with each other and with other researchers working on the same plots. Our goal is to integrate the results from the two project parts to obtain a better mechanistic understanding of how medium-term effects of biodiversity loss on ecosystem functioning are related to differential short-term responses to environmental events of forests with high vs. low tree diversity. This knowledge forms a basis for management to increase forest stability and ecological sustainability, including timber production and soil protection.

Prof. Dr. Bernhard Schmid (Project leader)
Dr. Yann Salmon
Rahel Bollinger (M.Sc.)

Prof. Dr. Keping Ma, Institute of Botany, Chinese Academy of Sciences, Beijing
Prof. Dr. Dali Guo, School of Environmental Sciences, Peking University
Prof. Dr. Jin-Sheng He, School of Environmental Sciences, Peking University
Prof. Dr. Rolf Siegwolf, PSI Villigen