雅鲁藏布江中游河岸交错带沙地土壤水分的空间异质性

Spatial variability of soil moisture on aeolian sandy land in riparian ecotone of middle reaches of Yarlung Zangbo River valley

土壤水分是制约西藏高寒河谷风沙化土地植物群落自然演替和人工促进植被恢复的重要因子之一,准确把握沙地土壤水分的分布状况,对指导正在进行的沙地植被恢复与重建具有重要实践意义。该文采用地统计学与GIS相结合的方法,以雅鲁藏布江中游河谷风沙化土地为对象,研究了河岸交错带沙地土壤水分的空间分布及不同类型沙地和沙丘部位的差异性。结果表明:1)试验地不同深度土壤含水率平均值为6.14%～14.20%,随着湿沙层深度的增加,土壤含水率平均值随之增大。各层土壤含水率均表现为强变异性。2)除0～20cm土壤含水率具有强烈的空间相关性外,其它各层土壤含水率具有中等的空间相关性。随着土层深度的增加,空间相关性减弱。不同深度土壤含水率的空间分布格局存在着较强的相关性,以20～40cm和40～60cm相关性最高。3)流动沙丘迎风坡和河滩地土壤含水率明显高于背风坡、沙砾地、沙丘顶。雅鲁藏布江河水丰枯变化、微地形和风沙运动则是造成不同类型沙地、沙丘部位土壤含水率差异的主要原因。

Soil moisture content is one of the restrictive factors of natural vegetation succession and artifical vegetation restoration in the alpine valley in Tibet. The purpose of this study is to characterize the distribution of soil moisture on different aeolian sandy land types, and to make inferences to guide the ongoing vegetation reconstruction. Taking aeolian sandy land in the riparian ecotone of the middle reaches of the Yarlung Zangbo River valley as a case study, geo-statistical and GIS methods were conducted to examine the spatial variability and vertical characteristics of soil moisture on. The results showed： 1） the mean soil moisture content at different depths on aeolian sandy land was from 6.14% to 14.20%, and decreased with the increasing depth of humid soil layer. The spatial variability of soil moisture was the strong variability; 2） Soil moisture content had a strong spatial correlation in the layer of 0-20 cm and a moderate spatial correlation in other layers. The spatial correlation decreased with the soil depth increased. The spatial distribution pattern of soil moisture between different soil depths had a significant similarity, and the highest was between 20-40 cm and 40-60 cm ; and 3） The soil moisture content varies with the micro-topograhpy, sandy land on flood plain 〉 windward aspect 〉 leeward aspect 〉 sandy gravel land 〉 top of sand dunes. The variations of water level, micro-topography and aeolian sand movement are the main factors to determine the differentiations of soil moisture content between different types of sandy land and parts of moving sand dunes.