黄土丘陵区小流域坡沟系统土壤水分时空变异与空间转换研究

Soil moisture is the core variable in the soil-plant-atmosphere continuum. It plays a significant role in a variety of ecohydrological processes including crop growing, vegetation restoration and soil erosion. To characterize catchment-scale spatiotemporal variability of soil moisture and understand the relations of soil moisture between gullies and hillslopes on the hilly region of the Loess Plateau, this project will conduct in situ soil moisture monitoring and measure relevant environmental variables including soils, topography and vegetation features in a typical small catchment. Classic and geo- statistical analysis and spatial interpolation methods are employed to analyze spatiotemporal characteristics, primary controlling actors, and time stability features of soil moisture. The revised time stability analysis and observation operators are used to probe the relations of soil moisture between hillslopes and gullies. Based on this, this project will investigate whether spatiotemporal features of soil moisture in gullies could be reliably estimated from measurements of adjacent hillslopes. This study will provide insights into catchment-scale soil moisture evaluation and the sustainability of the “Grain-for-Green” project in the hilly region of the Loess Plateau.

土壤水分处于土壤-植被-大气连续体的核心位置，对作物生长、植被恢复、水土流失等生态水文过程均具有重要影响。为揭示黄土丘陵区小流域坡沟系统土壤水分时空变异特征，科学认识坡面与沟道土壤水分关系，以典型小流域为研究单元，开展土壤水分定位监测试验和土壤、地形、植被等环境因子测定。采用常规统计分析、地统计分析以及空间插值等方法研究小流域坡面与沟道土壤水分时空变异规律、主要影响因素、及时间稳定性特征。采用改进的时间稳定性分析和观测算子等方法探讨坡面与沟道土壤水分空间转换关系，探索通过坡面土壤水分估算沟道土壤水分时空变异信息的有效途径。该研究可为黄土丘陵区小流域坡沟系统土壤水分评价和退耕还林（草）工程持续健康发展提供科学依据。

土壤水分是地球关键带的关键变量，对作物生长、水土流失、和植被恢复等地表过程具有重要影响。本项目以园则沟流域为单元进行小流域土壤水分连续定位观测，采用时间稳定性分析、地统计分析、经典统计分析等方法研究小流域土壤水分时空变异特征，探讨坡面与沟道土壤水分空间转换关系。研究发现沟道的存在增强了小流域土壤水分空间结构性强度和空间变异强度。小流域土壤水分空间变异强度主要受平均含水量的影响，但距平含水量与平均含水量的协方差显著影响了空间变异与平均含水量的关系，以及土壤水分时间稳定性。采用改进的时间稳定性分析方法、观测算子等方法能够较为准确地将坡面土壤水分转换为沟道土壤平均含水量，进而实现小流域坡面与沟道土壤水分的空间转换。另外，还发现覆盖措施显著改变了坡面枣园土壤水分时空分布。研究结果增强了对黄土丘陵区小流域土壤水分时空变异规律的认识，为该区复杂地形土壤水分的精确估算提供了有效方法。