长江源区高寒退化湿地地表蒸散特征研究

A study of evapotranspiration on the degraded alpine wetland surface in the Yangtze River source area2

青藏高原作为"亚洲水塔",对东亚乃至全球大气水分循环都有非常显著的影响.高寒退化湿地是高原上生态多样性的保证,也是水汽循环和地表径流的重要源地,其地气之间水分交换不但可以反映气候变化,而且也对生态环境保护具有重要意义.以长江源区隆宝滩湿地连续一年、每10分钟一次的观测资料为基础,利用FAO Penman-Monteith方法分析了长江源区高寒退化湿地蒸散量的变化特征及其与环境因子之间的关系.结果表明:1)牧草生长期,潜在蒸散量日、月变化特征显著;实际蒸散量整体表现为冬小、夏大,夏季蒸散贡献最大.2)观测期间,蒸散量远大于降水量,水分亏损严重,局地蒸散对降水的贡献较高.3)土壤温度对蒸散发过程影响显著,尤其是表层5 cm地温与蒸散发相关性较好,土壤湿度变化表明其为蒸散发过程提供了充足的水分.4)全年变化中,气温是影响蒸散的主要因素.晴天中,高寒退化湿地实际蒸散量与辐射具有几乎相同的变化趋势,气温对蒸散量影响较小,蒸散量与相对湿度呈现显著的反相关.

As a ＂water tower of Asia＂, the Tibetan Plateau has a large effect on East Asian and even global water cycle. The degrading alpine wetland over the plateau, working as an assurance of plateau ecological diversity, is an important origination of water and surface runoff, where land-air water exchange not only reflects the regional climate change, but also has great significance for ecological environment protection. The one-year data observed with 10-minute interval at Longbaotan wetland in the source area of the Yangtze River was analyzed by the method of the FAO Penman-Monteith to look for the evapotranspiration change over the degraded alpine wet- land and its relationship with environmental factors. The results showed that 1 ） during the grass growth season, the potential evaporation had distinct diurnal and monthly changes; the actual evapotranspiration was low in winter and high in summer with a peak in summer; 2） during the observation period, there was heavy water loss due to evapotranspiration exceeding precipitation; 3 ） soil temperature exerted an impact on the evaporation process; the soil temperature at 5-cm depth correlated more significantly with evaporation; the increase in soil moisture could provide plenty of moisture for evaporation process; 4 ） during a year, temperature is the key factor influencing the actual evapotranspiration; but in a sunny day during grass growth period, the evapotranspiration and radiation varies in the almost same pattern, and surface air temperature has less influence on the evapotranspiration, which correlates negatively with the relative humidity near surface.