Interactions between fire, vegetation and climate

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This project aims to improve the understanding on the interactions between fire, vegetation and climate. In particular, I will address when and where interactions between fire, vegetation and climate cause multiple stable states of vegetation.Multi-stability has implications for an ecosystem's resilience including the possibility for abrupt changes. Multiple stable states of vegetation due to fire-vegetation interactions are expected based on theoretical analyses, satellite data, field studies and simulation models. Due to different fuel characteristics and a different microclimate grasses support frequent fires, which hinders the establishment of trees. On the other hand the formation of a forest with coarse fuels and moister microclimate can exclude fires. This feedback between fire and vegetation stabilizes vegetation states with high or low tree cover. Until recently the feedback between fire and vegetation was only captured by regional or conceptual models. The implementation of a complex fire model in the JSBACH land surface model provided the first global picture of multiple stable states of vegetation due to a fire-vegetation feedback.JSBACH has the advantage of being a global model and the possibility of being coupled to the MPI-ESM Earth system model. However, regional vegetation models and offline (no coupling to atmosphere) models benefit from better evaluation with observations and a detailed process representation. Here I propose a comparison between models with different complexity (JSBACH, LPJ-GUESS, aDGVM, aDGVM2) to assess the robustness of the models sensitivity to climate and address how a different process representation influences the feedback between fire and vegetation. The land surface has a strong influence on climate through changes in albedo, transpiration and surface roughness. Thus, local fire-vegetation processes which alter the land surface state can trigger large scale transitions in climate. To investigate this scale interaction and assess potential effects on climate, I propose to use the MPI Earth System Model.In addition to investigating the modelled fire-vegetation-climate interactions, I aim to test the models with data. New high resolution satellite data products allow assessment of the response of fire occurrence to changes in vegetation cover. An analysis of these satellite datasets will provide a basis to evaluate the modelled sensitivity of fire occurrence to vegetation changes.The results of the proposed studies will be synthesized to address the questions when and where interactions between fire, vegetation and climate are important and what are the remaining gaps of knowledge on interactions between fire, vegetation and climate.