OPTIMIZED ROOTING DEPTH AND ITS IMPACTS ON THE SIMULATED CLIMATE OF AN ATMOSPHERIC GENERAL-CIRCULATION MODEL

Rooting depth determines how much water can be stored in the soil whic h is accessible to the vegetation for transpiration. Here, we derive a global distribution of rooting depth with an optimisation principle: A simple formulation of Net Primary Production (NPP) is incorporated i nto a General Circulation Model and then NPP is maximised in respect t o rooting depth. The obtained rooting depths are considerably larger t o those used in present-day models but are consistent with observation s. NPP increases substantially with the use of optimised rooting depth s, mainly in tropical regions during the dry season accompanied with e nhanced transpiration. The increased flux of latent heat leads to a co nsiderable decrease in 2m air temperature, which leads to a better agr eement with observations. We conclude that rooting depth is an importa nt vegetation property, especially in the tropics, and tropical defore station might have a much larger impact on climate than previously tho ught.