毛乌素沙地不同覆被类型土壤水分动态及其对降水的响应

Soil Moisture Dynamics and Its Response to Precipitation in Different Cover Types of the Mu Us Sandy Land

[目的]分析不同覆被类型下土壤水分时空变化特征及对降雨的响应,探讨覆被类型对土壤水文的重塑过程,为优化毛乌素沙地植物覆盖类型和提高土壤水分的植被承载力提供科学依据。[方法]以陕西榆林市毛乌素沙地典型覆被类型草地、沙柳地和裸地为研究对象,通过全年原位试验监测和经典统计学分析相结合的方法,分析0—150 cm土壤水分动态及其对降水的响应。[结果](1)在全年尺度,受植被根系分布和耗水差异的影响,典型覆被类型土壤水分可分为稳定期(12月至次年2月)、积累期(3—5月)、消耗期(6—8月)和恢复期(9—11月),降水补给土壤水分主要发生在积累期和恢复期。土壤剖面水分表现出明显的空间分异,草地在20 cm较高,沙柳地在50 cm和150 cm处较高。草地主要利用深度0—50 cm的土壤水,沙柳主要利用50—100 cm的土壤水。(2)沙柳地和草地的土壤水分在浅层(0—50 cm)对降水的响应比裸地慢,深层(50—150 cm)则比裸地快。(3)降水补给深度与降水量呈显著正相关,而响应滞后时间与降水历时呈显著正相关(p<0.05)。[结论]植被类型、降水历时、降水强度、冻融过程影响着土壤剖面水分再分配,主导植被类型在降水格局变化下的演替。

[Objective]The temporal and spatial variation characteristics of soil moisture and its response to rainfall under different cover types were analyzed,and the remodeling process of cover types on soil hydrology was discussed,which provided scientific basis for optimizing plant cover types and improving vegetation carrying capacity of soil moisture in Mu Us sandy land.[Methods]Grassland,salix land and bare land in Mu Us sandy land in Yulin City of Shaanxi Province were taken as research objects.The soil water dynamics in 0—150 cm layer and its response to precipitation were analyzed by combining annual in-situ observation and classical statistical analysis.[Results](1)At the annual scale,affected by the difference of vegetation root distribution and water consumption,the soil moisture of typical cover types could be divided into stable period(December to February of the following year),accumulation period(March to May),consumption period(June to August)and recovery period(September to November).Soil profile moisture showed obvious spatial differentiation,it was higher at 20 cm in grassland,it was higher at 50 cm and 150 cm in salix community.Plants in grassland mainly used soil water in 0—50 cm,salix mainly used 50—100 cm soil water.(2)The response of soil moisture to precipitation in shallow layer(0—50 cm)was slower than that in bare land,while that in deep layer(50—150 cm)was faster than that in bare land.(3)The depth of precipitation recharge was significantly positively correlated with precipitation,while the response lag time was significantly positively correlated with precipitation duration(p<0.05).[Conclusion]Vegetation type,precipitation duration,precipitation intensity and freeze-thaw process affect the redistribution of water in soil profile and dominate the succession of vegetation type under the change of precipitation pattern.