The role of canopy hydrological diversity and complexity on water balance and carbon sequestration during dry conditions: a modeling study

The importance and influence of forest to catchment hydrology have been well recognized. In the South Eastern U.S., Chapel Hill, NC, evapotranspiration by forest dominates almost 80% of the annual precipitation in long term average. Stomatal conductivity varies by tree species and its response to dry condition differently between evergreen and deciduous, and within their phonology groups. In this study, we simulated the catchment hydrology and forest ecosystem at a local catchment, Cane Creek, in the Chapel Hill triangle area using a spatially distributed, process-based hydro-ecological model, RHESSys. We incorporated characteristics of individual tree species to represent high hydrological diversity (e.g., maple, oak, pine), which has been modeled as either evergreen or deciduous (low hydrological diversity) in many studies. With tree species specifically modeled, we were able to investigate the role of tree species diversity and complexity on catchment hydrology. Local forest plant diversity, size, and density were provided by the U.S. Forest Services FIA, and tree species physiological parameters were obtained through researches at Duke Forest. High hydrological diversity canopy has higher water use and carbon sequestration than low hydrological diversity canopy. This result supports the optimality theory that emergent vegetation pattern in landscape maximizes ecosystem productivity and water use efficiency. Previous study emphasized this emergent pattern in terms of vegetation density along the hillslope gradient, and we further emphasized the emergent pattern in terms of hydrological diversity in this study.