拉萨河流域耕地不同尺度土壤水分影响因子

土壤水分影响因子的尺度差异及作用是其尺度依赖性研究的基础.本文以青藏高原拉萨河流域耕地土壤为对象，通过遥感影像分析和野外调查，在全流域和小流域尺度上分别布设样点115和49个，采用土钻法分3层（0～20、20～40、40～60 cm）抽取土壤样本，获取土壤水分含量，然后运用生态学冗余分析和统计分析，筛选出影响耕地土壤水分的主要因子.结果表明： 在全流域尺度，受气候、海拔影响，土壤水分呈西南 东北递增趋势，其中，河谷区耕地受河流侧渗补给影响，下层土壤水分高于上层；在小流域尺度，耕地土壤水分随海拔升高及坡度增大而减少，土壤贮水能力随石砾含量增多而减弱.研究结果为拉萨河流域耕地向高海拔扩张、作物结构调整、土地整理及灌溉设施布设提供了重要依据.

Factors influencing soil moisture at different scales of the Lhasa River basin,China.

The scale difference and role of factors influencing soil moisture regime are the basis of scale dependency study. This study, which selected farmland soils in the Lhasa River basin of the Tibetan Plateau as the research object, identified the main factors affecting the soil moisture using ecological redundancy analysis (RDA) and statistic analysis methods, based on data obtained by remote sensing technology and field surveys. The soil layers of 0-20, 20-40 and 40-60 cm were collected with the soil drilling method at each of 115 sampling sites distributed in the whole basin of the Lhasa River and 49 sampling sites in one of its sub watersheds. The results showed that soil moisture content in the Lhasa River basin, under the influence of climate and altitude, increased from southwest to northeast, and was higher in the lower soil layer than the upper layer due to water supplement by lateral seepage of the river. At sub watershed scale, farmland soil water content decreased with increasing the altitude and slope, and soil water storage capacity decreased with increasing the gravel content. The results were a significant support for the farmland expansion to higher altitude, adjustment of cropping structure, land consolidation, and construction of irrigation facilities in the region.