黄土高寒区小流域土壤水分空间变异与环境影响因子

针对区域流域尺度上土壤水分在地形、植被等要素协同作用下的空间异质性规律以及响应机制研究较少，以青海大通典型人工林小流域为研究对象，自坡脚向上延3个坡向（阴坡、半阴坡、阳坡）呈放射状选取3条样线带布设样点，采用统计学分析、主成分分析和冗余分析等方法研究生长季初末时期0—20，20—40，40—60，60—80，80—100 cm各层土壤水分空间变异特征，以及各环境因子（海拔、植被高度、植被冠幅、地上生物量、草本丰富度、草本盖度、枯落物干重）对其影响规律。结果表明：生长季末水分均值、最值均大于生长季初，各坡向体积含水率最值、均值均表现为阴坡>半阴坡>阳坡，各土层呈中等变异（10%阳坡>阴坡，在末期表现为阳坡>半阴坡>阴坡；水分采样点间隔在初期应在36.50~448.90 m，末期应在18.30~552.40 m；冗余分析结果显示，海拔是影响青海高寒区土壤水分异质性的主控因素，解释率为35.3%（p<0.01），草本丰富度次之，解释率为26.1%（p<0.01），植被高度与植被冠幅也有显著影响。研究结果可为青海黄土高寒区退耕还林小流域生态水文过程研究以及后续植被恢复提供数据与理论参考。

Spatial Variation of Soil Moisture and Its Environmental Influencing Factors in A Small Watershed in the Loess Alpine Region

There are few studies on the spatial heterogeneity law and response mechanism of soil water under the synergistic effect of topography, vegetation and other elements at the regional watershed scale. Taking the typical small watershed restored by artificial forest in Datong, Qinghai Province as the research object, three slope aspects (shady slope, semi-shady slope and sunny slope) were selected, and the sample points were laid out in three transect belts, which were in a radial pattern. Statistical analysis, principal componentanalysis and redundancy analysis methods were used to study the soil moisture spatial variation characteristics in 0-20 cm, 20-40 cm, 40-60 cm, 60-80 cm and 80-100 cm layers at the beginning and the end of the growing season, as well as the effects of environmental factors (altitude, vegetation height, vegetation canopy, aboveground biomass, herb richness, herb cover and dry weight of litter). The results showed that the average and maximum water content at the end of the growing season were both greater than those at the beginning of the growing season, and the maximum and average values of volumetric water content in each slope aspect followed the order of shady slope>semi-shady slope>sunny slope, and each soil layer showed a moderate variation (10%sunny slope>shady slope at the initial stage, and at the final stage the order was sunny slope>semi-shady slope>shady slope. The water sampling point interval should be from 36.50 to 448.90 m at the initial stage and 18.30 to 552.40 m at the final stage. The redundancy analysis results showed that altitude was the main controlling factor affecting soil moisture heterogeneity in the alpine region of Qinghai, with an explanation rate of 35.3% (p<0.01), followed by the herb richness, with an explanation rate of 26.1% (p<0.01).Vegetation height and vegetation crown width also had significant effects. The research''s results could provide data and theoretical reference for the study of the eco-hydrological process and the subsequent vegetation restorationin small watershed of returning farmland to forest in the loess alpine region of Qinghai.