Water and carbon fluxes of European ecosystems: An evaluation of the ecohydrological model RHESSys

This study investigated whether the regional hydro-ecological simulation system RHESSys is a suitable tool for long-term global change impact studies under selected climatic conditions of Europe, taking advantage of the strongly varying climate along elevational gradients in mountain regions. We performed a validation of RHESSys using daily, monthly and yearly data on (1) streamflow and snow cover in five Alpine catchments and (2) water and carbon fluxes at 15 EUROFLUX sites. The simulation results generally agreed well with observations. RHESSys reasonably reproduced daily and monthly streamflow, as well as the seasonal cycle and amplitude of typical Alpine discharge regimes. Furthermore, RHESSys was capable of capturing the key features of the carbon cycle of various forested ecosystems, including significant differences between managed and close-to-natural forests, and more subtle distinctions between coniferous and deciduous systems. Our analyses confirmed that RHESSys is a suitable tool for studying global change impacts on mountain hydrology. Regarding the simulation of the carbon cycle, this investigation detected some data and model limitations that are discussed in detail. Finally, suggestions for model improvements are made, mainly concerning the formulations of decomposition and respiration rates in biogeochemical models.