A numerical study on hydrological impacts of forest restoration in the southern United States
Landscape in the southern United States changed dramatically during the 1930s and the following decades when massive agricultural and abandoned logging lands were converted to forest lands through natural restoration and silviculture. The impacts of this forest restoration on hydrology were investigated in this study by conducting numerical experiments with a regional climate model. Climatic and hydrological conditions for the months of January and July during an 8-year period were simulated with prior and post forest conversion land cover, respectively. The assembled results of the simulations and experiments during the period indicate that overall precipitation decreases in July and increases in January in the restoration region (RR) in response to the restoration, mainly caused by the reduction in the corresponding prevailing winds due to increased surface roughness. Evapotranspiration and root-layer soil moisture increase in both months, mainly caused by the changes in vegetation and soil properties. Solar radiation increases due to smaller albedo, most of which is used to increase sensible heat. Large increases in July precipitation, evapotranspiration, and runoff in the remote central Midwest are found, resulting from the change in the large-scale atmospheric circulation. The implications of the results for the projected vegetation changes due to the climate change and the silviculture project in the Southeast in the future are discussed.