荒漠人工固沙植被区土壤结皮斥水性发展特征

土壤结皮深刻影响绿洲边缘固沙植被区的土壤水文过程。土壤结皮斥水性是量化上述影响的潜在指标。采用滴水穿透时间（WDPT）法，研究了河西走廊荒漠边缘不同建植年限梭梭植被区固定沙丘土壤结皮斥水性的时间演变规律及影响因素。结果表明：建植20 a后，丘顶与丘间地土壤结皮出现显著斥水性（WDPT>5 s），而丘坡土壤结皮无斥水性（WDPT<5 s）。丘顶土壤结皮斥水性与总有机碳、微生物量碳、有机碳C-H组分以及电导率显著相关（P<0.01）；而丘间地土壤结皮斥水性与黏、粉粒含量显著相关（P<0.01）。植被形成的“碳岛”及“盐岛”效应是丘顶土壤结皮斥水性形成的主要原因，而黏、粉粒在土壤表层的积聚是丘间地土壤结皮斥水性形成的主要原因。

Temporal evolution of soil water repellency in stabilized sand dunes in artificial sand fixation vegetation area on fringe of a desert

Soil crusts play profound effects on soil hydrology processes in sand fixation vegetation areas at the edge of deserts. Soil water repellency (SWR) is a potential parameter to quantify the hydrological effects of soil crusts. SWR was measured by the Water Drop Penetration Time (WDPT) method, to investigate the temporal evolution and influence factors of soil crust water repellency in sand dunes, which were stabilized by Haloxylon ammodendron of different planting ages on fringe of a desert. The results showed that SWR of soil crusts was appeared in crest and inter-dune depression (WDPT>5 s), instead of dune slope (WDPT<5 s), after 20 years of planting. The SWR of soil crusts at dune crest was significantly correlated with total organic carbon, microbial biomass carbon, C-H component of organic carbon, and electrical conductivity (P<0.01), whereas, the SWR of soil crusts at inter-dune depression was significantly correlated with the contents of clay and silt (P<0.01). The results indicated that the "carbon island" and "salt island" formed by vegetation are the reasons for the SWR formation of soil crust at dune crest, while the accumulation of soil fine particles is the reason for the SWR formation of soil crust at inter-dune depression.