西南高山亚高山区植被活动增强对区域蒸散的影响OA北大核心CSTPCD

[Objective]It is of great significance to clarify the influence of enhanced vegetation activity on evapotranspiration in the southwest alpine and subalpine mountains in order to optimize regional water resources allocation and ensure water resources security.[Method]Based on the MOD16 evapotranspiration indicators from 2001 to 2020,including actual evapotranspiration(ET),potential evapotranspiration(PET)and the ratio of actual to potential evapotranspiration(ET/PET),the influence and contribution of meteorological factors such as temperature(T),precipitation(P),relative humidity(RH),pressure(PRS),insolation(I),wind speed(WS)and vegetation factor NDVI on evapotranspiration indicators in the alpine and subalpine area of southwestern China were expounded by linear fitting,SEN trend analysis,partial correlation analysis,stepwise regression analysis and other methods.[Result]1)The peak of ET within one year lagged behind PET,and they showed spatial inconsistency.The annual ET ranged from 246.0 to 1 191.3 mm,with the peak occurring late July.The ET was higher in the subalpine section of upper Yarlung Zangbo River and the subalpine area of southern Xizang,and lower in the northern parts of the Nujiang River.Annual PET ranged from 538.0 to 2 314.9 mm,with higher values continuing from late May to mid-August.The PET in the southern parts of upper Yalong River and subalpine section of upper Jinsha River was higher.2)The regional average ET was 627.8 mm,showing a significant increasing trend(P<0.05)at a rate of 2.93 mm·a-1,and the significantly increased areas were mainly distributed in the upper Jialing River,the upper Min River,the Dadu River,the upper Yalong River,the subalpine section of upper Jinsha River,the upper Lancang River,and part of the Nujiang River.The regional average PET was 1 500.6 mm,showing an insignificant decreasing trend at a rate of 2.57 mm·a-1,and the decreased areas were mainly distributed in the subalpine section of upper Jinsha River,the upper Yalong River,and the subalpine area of southern Xizang.The regional average ET/PET was 0.43,showing a significant upward trend(P<0.05).3)The order of the main influencing factors for ET was T>P>NDVI>RH>PRS>I>WS,for PET was T>I>P>RH>WS,and for ET/PET was T>RH>NDVI>I>PRS.4)The increase of ET was mainly caused by the enhanced vegetation activity,and the area dominated by the increase of NDVI accounted for nearly 63%.The decrease of PET was mainly related to the reduced insolation.The positive effects of increasing NDVI and decreasing insolation offset the negative effects of increasing temperature on ET/PET,resulting in the increase of ET/PET.The changing direction of ET/PET in the Budyko model during the study period indicated a shift from water limit to energy limit.[Conclusion]The enhanced vegetation activity in the alpine and subalpine area of southwestern China in the past 20 years have had a significant impact on regional evapotranspiration.Our results demonstrate that the long-term sustainability of water balance and soil water supply in the watersheds deserves more attention.