Estefanía Muñoz, Andrés Ochoa, Germán Poveda, Ignacio Rodríguez-Iturbe

This paper presents an extension of the stochastic ecohydrological model for soil moisture dynamics at a point of Rodriguez-Iturbe et al. (1999) and Laio et al. (2001). In the original model, evapotranspiration is a function of soil moisture and vegetation parameters, so that the model is suitable for water-limited environments. Our extension introduces a dependence on maximum evapotranspiration of available solar radiation, and thus our extended model is suitable for both water- and energy-limited environments. Furthermore, an analysis of the daily relationship between available energy for photosynthesis and transpiration through the stomatal conductance is carried out. This study regards the Penman-Monteith equation to model transpiration, the Leunings stomatal conductance approach, the C3 photosynthesis model of Farquhar et al., and the FLUXNET database. Results are upscaled from half-hourly to daily scale, introducing an expression of transpiration in terms of the available radiation. The sensitivity of the model is analyzed using four dimensionless groups, and the long-term water balance is evaluated for distinct values of available energy.