Coupling LPJ-GUESS with ParFlow for Integrated Vegetation and Surface-subsurface Hydrology simulations

Climate change likely accelerates the global hydrological cycle, which poses escalating impacts on human health and the social economy. Soil and groundwater water flow influence vegetation processes by affecting the timing and amount of plant available water. However, most models do not comprehensively represent the interactions between vegetation dynamics and lateral surface-subsurface water processes, which hinders a full understanding of catchment and regional water and carbon fluxes in a changing climate. This study incorporated a fully integrated three-dimensional groundwater flow and overland flow model ParFlow into the dynamic vegetation model LPJ-GUESS to investigate the influence of lateral water connection on vegetation composition and ecosystem carbon cycle. We conducted the stand-alone LPJ-GUESS and the fully coupled LPJ-GUESS-ParFlow simulations in the Yangtze River and the Danube River Basin to assess lateral water flow on simulated hydrological variables, vegetation composition and carbon cycles, as well as their response to climate change. This fully coupled model showed improved performance in simulating catchment soil moisture and runoff, especially for the areas with steep slopes. The coupled model offers a mechanistic framework encompassing well-defined vegetation dynamics, surface-subsurface water interactions, and ecosystem biogeochemical processes, which could be tested in many other catchments to thoroughly study climate-induced modification on plant-water-carbon interactions.