中文摘要：

蒸散是陆地生态系统水分循环的重要分量，研究典型生态系统的蒸散规律有助于认识水分循环过程，进而为水资源合理利用提供依据．本研究基于涡度相关法研究了2003—2011年海北高寒灌丛草甸生态系统的蒸散量变化特征及水分收支状况．结果表明：2003—2011年，研究区蒸散量的季节变化明显，最大值一般出现在生长旺季的7—8月，达4．4—5．7mm·d-1；最小值多出现在1月或12月（0．09±0．04mm·d-1）．蒸散量的年际动态明显，为451．3～681．3mm，其中，生长季占70％以上．年蒸散量与年降水量之比的平均值为1．06±0．17，表明该生态系统的年水分收支状况基本平衡，几乎所有的降水都以蒸散的形式消耗．

英文摘要：

Evapotranspiration （ET） is an important component of hydrological cycle of terrestrial ecosystem. To study the seasonal and interannual ET variation patterns of typical ecosystems is es- sential to better understand the water cycle process and to provide reference for the rational utiliza- tion of water resources. By using eddy covariance method, this paper studied the seasonal and inter- annual variation characteristics of ET and water budget in an alpine shrub meadow ecosystem in Haibei of Qinghai from 2003 to 2011. There was an obvious seasonal variation of ET in the study ar- ea in 2003-2011, with the maximum （4.4-5.7 mm . d-1） in the vigorous growth season （July- August） and the minimum （0.09±0.04 mm .d-1 ） in January or December. The annual ET varied greatly among the nine consecutive years, being 451.3 mm in 2010 and 681.3 mm in 2007. More than 70% of the annual ET occurred in the growth season from May to September. The average ratio of annual ET to annual precipitation was 1.06 ±0. 17, indicating that the water budget of this ecosystem was nearly balanced at year scale, and almost all the precipitation was released into at- mosphere by ET.