1 Department of Chemical and Biochemical Engineering, Technical University of Denmark2 Ecosystems Programme, Department of Chemical and Biochemical Engineering, Technical University of Denmark3 Risø National Laboratory for Sustainable Energy, Technical University of Denmark
Climate change factors such as elevated CO2 concentration, warming and changes in precipitation patterns have been shown to affect terrestrial carbon (C) cycling. The objective of this Ph.D. project is to track recently assimilated C into belowground compartments to investigate the effects of climate change on belowground C allocation. The impacts of climate change as single and combined treatments were applied to heath/grassland vegetation and the short-term terrestrial C turnover was investigated using in-situ 13CO2 pulse-labeling. We developed a mobile and low-cost pulse-labeling setup applicable in remote natural environments. We present evidence that our new system works reliablyand leads to results similar to former grassland pulse-labeling experiments. Allocation of recently assimilated C into roots and the microbial biomass was often similar among climate treatments, but C allocation patterns into microbial functional groups were treatment dependent. We observed a delayed C allocation into microbes under drought and a faster C flow through the microbial community under elevated CO2 conditions. Especially the importance of actinomycetes in the utilization of recently assimilated C can have major impacts on the C balance under changing climatic conditions. A comparison of C allocation under ambient and simulated future climatic conditions showed that the terrestrial C balance might be changed by reducing soil organic matter mineralization. Our results suggest that the impact of future climatic conditions may change belowground processes involved in C cycling and that heath/grassland soils have the potential to serve as C sinks in the future. To confirm these results, a short-term C balance for the conducted study is needed to reveal if observed C allocation into different microbial communities affects the short-term C balance on the ecosystem scale.