Abstract: Water is an important factor restricting the ecological development of semi-arid areas,and evapotranspiration (ET) is an important process of land water consumption. Based on the multi-year water flux,meteorological and vegetation data of the Duolun and Xilinhot grassland sites in semi-arid area of Inner Mongolia,this paper analyzed the ET change characteristics of the two typical grasslands and their responses to vegetation growth and main meteorological factors,which can provide scientific guide for the continuous development and protection of semi-arid grasslands. Results showed that the average annual ET of Duolun and Xilinhot sites was 417.15 mm and 440.20 mm and ET in the growing season accounted for 75.75% and 72.38%,respectively. The change course of ET during the year was unimodal,which was significantly positively correlated with energy factors,water factors and vegetation condition (P<0.01). Path analysis further showed that the monthly ET changes of the two sites were mainly driven by the direct effect of net solar radiation,and then influenced by the indirect effects of leaf area index,precipitation and soil moisture.

Key words: Evapotranspiration, Grassland, Path analysis, Semi-arid area

摘要： 水分是制约半干旱区生态发展的重要因素，而蒸散（Evapotranspiration，ET）是地表水分消耗的重要过程。本文基于内蒙古半干旱区多伦和锡林浩特草地站多年通量、气象和植被数据，分析两个典型草地ET变化特征及其对植被和主要气象因子的响应，为半干旱区草地资源的持续开发与保护提供参考。结果表明：多伦站和锡林浩特站多年均ET总量分别为417.15 mm和440.20 mm，其中生长季ET分别占年总量的75.75%和72.38%。两站ET年内变化均呈单峰型，和热量因子、水分因子与植被状况均呈显著性正相关关系（P<0.01）。通径分析表明，两站ET变化均主要受到太阳净辐射直接作用的驱动，其次受到叶面积指数、降水和土壤含水量的间接影响。

关键词: 蒸散, 草地, 通径分析, 半干旱地区