黑河下游胡杨林生态系统土壤蒸发模拟改进

Improvement of Soil Evaporation Modeling for a Populus euphratica Forest Ecosystem in the Lower Reaches of the Heihe River

水分是限制干旱、半干旱地区植被生态系统恢复的重要因素之一,合理量化长时间尺度下生态系统中的土壤蒸发量及其变化趋势,对于提高生态系统水资源利用效率具有重要意义。基于黑河下游额济纳绿洲七道桥胡杨林保护区实测数据,分析了胡杨林生态系统土壤蒸发和蒸散发的变化趋势及其与环境因子的相关性,通过Shuttleworth-Wallace模型和改进的双源模型中土壤蒸发的计算公式对其进行模拟,对比分析了二者的模拟精度及参数敏感性,结果表明:(1)土壤蒸发和蒸散发各月的日变化及整个试验期内的变化均呈先升高后降低的单峰变化趋势;(2)胡杨林生态系统土壤蒸发在蒸散发中所占比例的变化范围为30.2%~72.2%;(3)净辐射对土壤蒸发的影响最显著;(4)改进的双源模型中,土壤蒸发的计算公式可以不考虑复杂阻力参数的计算过程,且与传统的双源SW模型相比具有更高的模拟精度。研究提出了适用于干旱区森林植被生态系统中土壤蒸发模拟的双源优化模型,为土壤蒸发模拟提供了新的思路与方法。

Water is one of the important factors limiting the restoration of ecosystems in arid and semi-arid regions. Quantifying soil evaporation and its change trend over a long time scale is of great significance for improving water use efficiency. Based on the measured data of the Qidaoqiao Populus euphratica forest reserve in Ejin Oasis in the lower reaches of the Heihe River, we analyzed the variation trend of soil evaporation and evapotranspiration, and their correlation with the environmental factors, and simulated soil evaporation using the formula of the Shuttleworth-Wallace model and improved dual-source model. The accuracy and parameter sensitivity of each model were compared and analyzed, and the main conclusions were as follows.(1) The diurnal variation of soil evaporation and evapotranspiration increased firstly, and then decreased in each month and the whole experiment period, respectively.(2) The ratio of soil evaporation to evapotranspiration in the P. euphratica ecosystem varied from 30.2% to 72.2%.(3) Net radiation has the most significant effect on soil evaporation.(4) In the improved dual-source model, the calculation formula of soil evaporation does not need consider the calculation process of the complex resistance parameters, and has higher simulation accuracy than the traditional dual-source SW model. In this study, a dual-source optimal model for soil evaporation simulation in the forest ecosystems in arid areas is proposed, which can provide a new idea and method for soil evaporation simulation.