Impacts of devegetation on the temporal evolution of soil saturated hydraulic conductivity in a vegetated sand dune area

Abstract

Soil saturated hydraulic conductivity (K S ) is partly affected by vegetation activities, which can either increase K S by enhancing macropore flow or reduce K S by clogging pore space. Despite the complex interactions of K S with vegetation, the impact of devegetation on K S has not been adequately addressed, particularly in regions that are prone to drought-induced devegetation. In this study, the impacts of devegetation on K S in a native grassland-stabilized sand dune area were investigated by artificially controlling surface vegetation at an experimental site in the Nebraska Sand Hills. The experimental results revealed that the temporal evolution of K S at the site was mainly affected by the erosion processes triggered by devegetation. Over a short-term (about 1 year), the impact of devegetation on K S was negligible, owing to that the existence of dead root systems prevented erosion processes. By comparison, the long-term impact of devegetation on K S emerged when devegetation-induced erosion processes exposed deeper soil layers with higher K S . Particularly, the dunetop locations that experienced higher erosion rates had larger temporal changes in K S . Thus, the impacts of devegetation on K S mainly depended on two factors (i.e., time and topographic locations) that were related to erosion processes in this native grassland-stabilized sand dune area. To further investigate the ecohydrological implications of the temporal change in K S , a newly developed ecohydrological model was also employed, and the simulation results showed that the impacts of changes in K S on water balance components and biomass production were non-negligible and highly nonlinear. In spite of previous studies, the findings presented here demonstrate the close tie between near-surface hydrology and land surface evolution processes controlled by vegetation in sand dune areas, and highlight the importance of coupling eco-hydro-geomorphic interactions in the context of climate change.