黑河流域高寒草甸生态系统水分收支及蒸散发拆分研究

水分收支是对水循环要素降水、蒸发蒸腾、径流以及土壤贮储水量变化等的定量刻画,对水资源的可持续开发及利用至关重要。基于黑河流域阿柔观测站2014和2015年水文气象观测数据,运用水量平衡理论,定量的评估了高寒草甸生态系统的水分收支动态,并结合双源模型对高寒草甸生态系统蒸散发(植被蒸腾和土壤蒸发)进行拆分及评价。研究结果表明(1)在生长季(5—9月)植被蒸腾是高寒草甸生态系统主要的耗水形式,2014和2015年生长季平均蒸散比(T/ET)分别为0.74和0.79;(2)土壤水分的剧烈变化主要发生在0—40 cm处,且受冻融过程影响显著;(3)在降水较多的年份(2014)高寒草甸生态系统水分收支基本平衡,且不受冻融影响的月份(6—9)有地表径流产生约42 mm;在正常年份(2015),生态系统呈现水分亏缺,亏缺量约为134 mm,6—9月约亏缺26 mm;(4)模型估算蒸散发(ET)与实测蒸散发具有很好的一致性,相关系数可达0.90,敏感性分析表明模型输入变量对蒸散发(ET)及蒸散比(T/ET)产生的误差较小,双源模型可以很好地实现对高寒草甸生态系统蒸散发(ET)的拆分。

Water budget and evapotranspiration partition in an alpine meadow ecosystem in the upstream of the Heihe River, China

Water budge is an important indicator for water resource sustainability. It is critical to quantitatively analyze the water budget, yet challenging due to complex and dynamic hydrological processes such as precipitation, runoff, evapotranspiration, and soil water storage. In this study, we estimated the dynamics of water budget in an alpine meadow ecosystem based on the meteorological observation during the years 2014 and 2015 at the A''rou site in the Heihe River Basin (HRB). In addition, we partitioned the process of evapotranspiration into vegetation transpiration and soil evaporation by using the two-source model to understand the process of water budget. Our results showed that vegetation transpiration was the major cause of water consumption in the alpine meadow ecosystem during the two-year growing season. Mean ratios of transpiration to evaporation (T/ET) during the growing seasons of 2014 and 2015 were 0.74 and 0.79, respectively. The surface soil layer (0-40 cm) changed significantly compared with the other soil layers and dramatically affected by the freeze-thaw process. In the rainy year (2014), the water budget remained basically balanced, and a 42-mm surface runoff was generated during the growing season; however, in 2015, evapotranspiration exceeded precipitation, leading to a decrease in soil moisture. The results estimated from the two-source model were consistent with the observed data, with a correlation coefficient of 0.90. The analysis of model sensitivity indicated negligible error from the variables of model input. The above results demonstrated the successful application of the two-source model for the partition of evapotranspiration in an alpine meadow ecosystem.