Influences of subsurface heterogeneity and vegetation cover on soil moisture, surface temperature and evapotranspiration at hillslope scalesInfluence des hétérogénéités de surface et du couvert végétal sur l’humidité du sol, température de surface et évapotranspiration à l’échelle du versantInfluencia de la heterogeneidad subsuperficial y de la cobertura de vegetación en la humedad del suelo, temperatura superficial y evapotranspiración a escala de laderas山坡尺度上地下非均质性和植被对土壤水、地表温度和腾发的影响Influências da heterogeneidade subsuperficial e do coberto vegetal na humidade do solo, na temperatura superficial e na evapotranspiração à escala das vertentes de encostas

Physical processes are at the root of determining hydrologic response at all scales. Here, the physical mechanisms linking (1) subsurface heterogeneities to soil moisture and (2) resulting land-surface energy feedbacks to the atmosphere, are examined at the hillslope scale using a fully coupled surface-subsurface-land-surface model, ParFlow. A hillslope with a heterogeneous subsurface and uniform topography was modeled numerically using summer atmospheric conditions and a single precipitation event under controlled boundary conditions in order to isolate the contribution of hydraulic conductivity to land-surface hydrological processes and energy interactions. Patterns of subsurface hydraulic conductivity are shown to govern soil-moisture distribution at the hillslope scale following precipitation. This variability in soil moisture is closely linked to the variability in land-surface energy feedbacks. The role that vegetation plays in subsurface soil moisture and land energy communications is also examined. Results show that hillslope soil moisture variation is first established by patterns in vertical hydraulic conductivity, while later on in the dry-down period, vegetation exerts greater control on the land-surface energy fluxes and controls the rate of hillslope dry down. Furthermore, as compared to bare-soil simulations, grass-cover simulations show an increase in near-surface soil moisture despite water up-take along the rooting depth.