Streamflow decreases in response to acid deposition in a subtropical forest watershed in China

Streamflow reductions have been attributed to the impacts of soil nutrient availability on plant transpiration, connecting soil biogeochemical and hydrological processes. Here we conducted a plot-scale acid addition experiment and monitored long-term hydrology in a subtropical watershed to provide direct evidence for the underlying mechanisms of these connections. These results showed that acid deposition enhanced plant growth and thus increased plant transpiration in the early treatment period. It indicates that plants can increase their transport of water and nutrients to satisfy physiological demands under continuous acid deposition. Acid deposition mainly contributed to increased evapotranspiration and decreased streamflow at the watershed scale. These results provide complementary evidence of plants adjusting to acid deposition-induced changes in soil nutrient availability and these acclimations result in streamflow reductions at the watershed scale. Our results call for integrating forest biogeochemical feedback into watershed hydrology.