为了研究长江源区植被盖度变化对高寒草甸蒸散过程的影响,在长江源区选择坡向、坡型和坡度趋于一致,植被覆盖度分别为92%,65%和30%的高寒草甸建立天然观测场,采用小型蒸渗仪称重法观测计算不同覆盖条件下的高寒草甸蒸散量,分析了不同时期蒸散的动态变化特征和主要驱动因子。研究结果表明,在生长前期,随着植被盖度降低,高寒草甸蒸散量呈增加趋势;而在生长期、生长后期和冻结期,随着植被盖度降低,高寒草甸蒸散量呈减小趋势,且盖度变化对生长期蒸散量的影响尤为显著。不同时期主导蒸散变化的因子存在差异,热量因子在生长前、后期起主导作用,而在生长期起主导作用的是水分因子。

To investigate actual evapotranspiration(ET)under different degrees of vegetation coverage,three plots of alpine meadow were established on the places where the topography was of the same slope,direction,and shape and where the degrees of vegetation coverage were 92%,65%,and 30% in the headwaters of the Yangtze River.The lysimeter method was used to calculate ET of alpine meadow under different degrees of vegetation coverage.The characteristics of ET and the dominating factors in four periods were analyzed.Results show that ET increased with the reduction in vegetation coverage in the per-growth period,while ET decreased with the reduction in vegetation coverage in the growth period,post-growth period,and the frozen period.The change of vegetation coverage influenced ET in the growth period very obviously.The dominating factors varied with different periods.Heat played a leading role in the per-growth period and the post-growth period and moisture played a leading role in the growth period.