Evapotranspiration and its source components change under experimental warming in alpine meadow ecosystem of Qinghai-Tibet Plateau

摘要

Climatic warming is considered as one major driving force for alpine meadow degradation in the Qinghai-Tibet Plateau as warming affects soil moisture through accelerating the evapotranspiration.Partitioning evapotranspiration(ET)into soil evaporation(Ea)and plant transpiration(Tr)is important for understanding soil moisture change mechanism,and their differential responses to climatic warming.A field experiment was conducted to investigate the climatic warming effects(W1: 130 W m-2 and W2: 150 W m-2 additional radiation)on soil moisture,ET and its components(i.e.Ea and Tr)of alpine meadow in the Qinghai-Tibet Plateau.ET was calculated using energy balance model and soil moisture correction function.Warmrainy season Ea was modeled by multiple linear regession with latent heat,soil temperature at 20 cm and Tr was quantified as the difference between ET and Ea.Warming significantly decreased soil moisture in shallow layers(10 and 20 cm depth).Annual ET and its components were significantly stimulated by warming.Annual ET increased by 92.65 and 89.18 mm in W1 and W2 treatments.Ea was 51.7-57.8％of the ET and decreased with warming level.Annual Ea increased by 29.12 and 33.37 mm,and Tr increased by 63.53 and 55.81 mm in W1 and W2 treatments,respectively.The results suggest that warming induced Tr increase accounted for most ET change and the shallow soil layer moisture decrease in growing season of the alpine meadow in Qinghai-Tibet Plateau.