陕北黄土区流域分水线土壤干层分布

陕北黄土区切沟密集，地形支离破碎，地形与植被共同作用下土壤水分状况较为复杂。通过长期定位观测深剖面土壤含水量，分析了流域分水线深层土壤水分时空动态及干层分布特征。研究结果表明:生长季0~3 m土层土壤水分亏缺，生长季后1.2 m以上土层亏缺水分得到补充，但该深度以下土壤水分含量未得到恢复，其中2.6~6.4 m深度范围缺水严重，流域分水线土壤水分含量出现明显的垂直分层现象；各观测点土壤含水量随深度的分布曲线、极值出现深度和干层深度范围不同，剖面干层随各分水线走向表现出不连续分布的特点；分水线干层平均起始深度为2.03 m，厚度为0.4~8 m，干层土壤含水量均值为9.03%，干层厚度与起始深度和干层土壤含水量均呈负相关关系。比较而言，陕北黄土高原干层发育严重程度较突出。相关研究结果可为流域土壤水资源分布及土壤水库功能评价提供理论依据。

Distribution of dried soil layers on the dividing waterline in the gully area of the Loess Plateau

The northern Loess Plateau is characterized by dense gullies and fragmented topography. The status of soil water shortage in this region is complicated under the combined effects of topography and vegetation. In this research, we designed 15 observational sites on 3 dividing waterlines in the gully area of Liudaogou catchment in Shenmu country. Based on long-term observation with neutron probe, we studied the spatial-temporal distribution of deep soil moisture as well as the characteristics of dried soil layer. The specific results were showed as follow:① Soil moisture was in deficit in 0-3 m soil layers in the growing season, then it was recharged above 1.2 m depth. Soil moisture under 1.2 m depth did not recover and soil water deficit was serious in 2.6-6.4 m soil layers. ② The profile distribution of soil water content and relevant depths of extreme values as well as the occurred range of dried soil layers were inconsistent among different observational points. Moreover, the profile distribution of dried soil layers along the dividing waterline was discontinuous. ③ The thickness of dried soil layers varied within the range of 0.4-8 m, the average formed depth of dried soil layer and mean soil moisture within the dried soil layer were 2.03 m and 9.03%, respectively. The former had negative linear correlations with the latter two quantitative indices. Compared with the average status of the Loess Plateau, dried soil layers in the gully area was more prominent. These results were expected to provide help for comprehensively evaluating the function and status of soil water reservoir in gully area.