| Abstract: | - 1 A zero‐dimensional model of local atmosphere–vegetation interaction is presented. The model includes essentials of water related two‐way feedbacks, such as the influence of vegetation on evapotranspiration, and the impact of temperature and drought on biomass growth and mortality. The simple model serves as a framework for the preliminary investigation of vegetation related feedbacks under climate change scenarios.
- 2 Model simulations for a mid‐latitude forest area for an increasing external forcing indicate a transient growth of biomass up to a critical forcing, where drought stress begins to dominate the response. Beyond, biomass decreases, reinforced by the reduced evapotranspiration of a diminished vegetation, leading to an additional temperature increase (biomass–evapotranspiration feedback).
- 3 The implementation of an additional feedback loop based on the hypothesis that drought stress implies not only a reduction in above‐ground biomass, but also a net reduction in roots and therefore a reduction of the amount of water accessible to the plants for transpiration, leads to the occurrence of a second stable state in the atmosphere–vegetation system. In the bistable regime, a moderate perturbation can trigger an abrupt change of state.
- 4 The present conceptual investigations underline the importance of a dynamic vegetation subsystem in transient climate change, and stress in particular the possible role of feedbacks related to root dynamics.
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