Augmenting the multiscale hydrologic modeling system with adequate vegetation dynamics for improved representation of coupled water and carbon cycles

As climate is changing, future functionality and resilience of terrestrial ecosystems are expected to change in numerous ways. However, these projected changes remain uncertain. One of the major sources of uncertainty is the representation of vegetation dynamics which directly respond to increased temperature and ambient CO2 concentrations and thereby alter transpiration. Many of the existing hydrologic models representing components of the water cycle have a very simplified representation of vegetation dynamics that are not able to represent this link.  In this study we aim to augment the existing mesoscale Hydrologic Model (mHM) with a low complexity dynamic vegetation model (DVM). This will provide the model with improved capabilities to represent the coupled water and carbon fluxes. Our analyses focus on representing the vegetation (i.e. biomass growth) including fluxes such as gross and net primary productivity and their inter-linkages to water storage and fluxes (e.g., soil moisture and evapotranspiration) across biomes (e.g., grasslands). These inter-linkages, which are spatially and temporally variable and scale-related, are crucial for adequately representing the coupled water and carbon cycle. For example, the adequate representation of soil moisture is essential to capture the mechanistic response of plant productivity to changes in soil moisture; and vice versa especially under extreme environmental conditions. In this presentation, we will discuss the simplified structure of the DVM based on a Light Use Efficiency (LUE) model concept and couple the model components to the mHM. Furthermore, the coupled simulation results of different water and carbon fluxes will be presented for a test region in Central Germany.