An integrated model of land surface, subsurface flow, and ecosystem processes to study hillslope vegetation function

Abstract:

Tropical forests play an important role in the coupled land-atmosphere system by contributing a large fraction of precipitation through evapotranspiration. However, changes in water availability due to climate change may shift the composition of tropical forests, with consequential impacts on the regional and global water cycles. Topographic heterogeneity and lateral subsurface flow at the hillslope scale of 1000 m or less may have outsized impacts on tropical forest distribution and functioning and hence land-atmosphere flux exchanges. However, vegetation canopy structure and functioning and finer‐scaled processes such as subsurface lateral flow are typically missing in Earth system models to realistically represent soil hydrology and groundwater dynamics that control plant available water.

We integrated the E3SM Land Model (ELM), an ecosystem dynamics model (FATES), and a three-dimensional hydrology model (ParFlow) to explicitly resolve hillslope topography and subsurface flow for better understanding of the processes that drive tropical forest dynamics. E3SM (Energy Exascale Earth System Model) is a state-of-the-science fully coupled Earth system model configurable at low-to-high resolutions. The FATES model (Functionally Assembled Terrestrial Ecosystem Simulator) is a numerical terrestrial ecosystem model that represents ecosystem demography, canopy structure, and ecosystem function. ParFlow is a parallel, integrated hydrology model designed to simulate spatially distributed surface and subsurface flow at hillslope scale. Numerical experiments will be performed to understand how hydrologic processes at hillslope scale modulate water available to plants and how vegetation structure and function respond to a changing climate at selected tropical sites along gradients of water availability.