Evapotranspiration from a primary subtropical evergreen forest in Southwest China

Abstract

AbstractEvapotranspiration (ET) was observed over a 5‐year period at a primary subtropical evergreen forest in southwest China. The study used the eddy covariance method and quantified the precipitation, throughfall, stemflow, soil evaporation, and routine meteorological parameters to analyze the contributions of stand‐level transpiration and canopy interception loss to the total ET. The annual ET ranged between 785 and 901 mm. The average ratios ET–potential evapotranspiration were 0.45 and 0.87 during the dry and wet seasons, respectively. The relative contributions of soil evaporation, stand‐level transpiration, and canopy interception loss to ET were quantified in order to understand their roles in today's climate and in a potential future climate. Solar radiation was a driver for ET, although the occurrence of drought limited the tree transpiration and thus ET. Specifically, deep soil moisture was an important driver of ET during the dry season. During the wet season, the vapor pressure deficit became one of the main drivers. Although the current study did not collect specific data for the effect of fog on ET, fog likely plays an important role in the ecohydrologic system and deserves further investigation. Although the hydrological system is currently stable, it is anticipated that the groundwater recharge from the ecosystem may be largely reduced in the future, likely through climate change and an associated positive temperature–ET feedback loop.