Plant photosynthesis represents the largest sink for atmospheric carbon dioxide (CO2). Soil respiration, in contrast, is the largest source of CO2. The balance between these two fluxes is therefore essential for the stable concentration of this greenhouse gas in our atmosphere. Mountain ecosystems have a strong capacity for accumulation of carbon (C) in the soil, due to cold temperatures limiting decomposition rates of soil organic matter. With warmer climate, however, decomposition rates increase, releasing more nutrients for plant growth and promoting taller vegetation. Such vegetation shifts are a particular challenge to estimations of net ecosystem C fluxes under climate change, as a multitude of plant-soil feedbacks take place.
This research project investigates whether increased plant productivity and forest expansion in mountain areas under climate and land-use change causes shifts in the community structure and function of decomposing microorganisms and thereby accelerate the soil C cycle. Focus is laid on the activity of characteristic mycorrhizae symbiotically associated with different vegetation types. The project evaluates diverse ecological processes from the plant to the ecosystem scale, based on mechanistic lab experiments and realistic field observations. This hierarchical approach improves our understanding of the terrestrial carbon cycle and inform policy makers on which adaptive strategies are sustainable for mountain ecosystems under climate change.