高寒半干旱区沙地植被土壤水分变化特征及其影响因素

为揭示高寒半干旱区不同降雨强度对植被差异下沙化土地土壤含水量变化过程的影响。以青海共和盆地东缘黄沙头乔木、灌木和裸地为研究对象,基于2020、2021和2022年5月-9月植物生长季土壤含水量、降雨量和细根分布监测数据,分析2020年、2021年、2022年各生境0-200 cm深度土壤水分对小雨、中雨、大雨的响应。连续动态监测结果表明,大雨、中雨条件下,随土层深度的增加土壤水分对降雨的响应时间延长。乔木林和灌木林土壤水分对中雨、大雨最大响应深度为70 cm、100 cm,裸地对中雨、大雨最大响应深度为50 cm、100 cm。随土层深度的增加,小雨对乔木、灌木、裸地土壤水分的补充作用逐渐降低;中雨对灌木林土壤水分的补充作用逐渐降低,乔木林与之相反;大雨时乔木林、灌木林变异系数呈现S型变化,因此大雨对其土壤水分的补充存在明显的分层利用现象。不同植被类型土壤水分空间变化差异以及对降雨的响应受植被冠层截留对降水再分配的影响,土壤含水量与环境因子间的主成分分析表明,郁闭度、叶面积指数、150-200 cm土壤容重、细根生物量密度、根表面积密度、根长密度、比根长是反映研究区土壤水分的显著因子(P ＜ 0.05)。研究表明不同降雨强度植被土壤含水量存在明显差异,高寒半干旱区沙化土地乔、灌植被的建植可提升深层土壤储水能力;结果可为沙化土地恢复和水土流失防控提供科学依据。

Characteristics and influencing factors of Soil Moisture Changes in Sandy Vegetation in Alpine and Semiarid Areas

To reveal the impact of different rainfall intensities on the changes in soil moisture content of sandy land under vegetation differences in high-cold and semi-arid regions. Based on the monitoring data of soil moisture, rainfall, and fine root distribution during the plant growth season from May to September 2020, 2021, and 2022, the response of soil moisture at a depth of 0-200 cm in each habitat to light, moderate, and heavy rain was analyzed using trees, shrubs, and bare land in the eastern edge of the Qinghai Gonghe Basin. The continuous dynamic monitoring results indicate that under heavy and moderate rain conditions, the response time of soil moisture to rainfall increases with the increase of soil depth. The maximum response depths of soil moisture in tree and shrub forests to moderate rain and heavy rain are 70 cm and 100 cm, while the maximum response depths of bare land to moderate rain and heavy rain are 50 cm and 100 cm. As the depth of the soil layer increases, the supplementary effect of light rain on soil moisture of trees, shrubs, and bare land gradually decreases; The supplementary effect of moderate rain on soil moisture in shrublands gradually decreases, while in tree forests it is the opposite; During heavy rain, the coefficient of variation of tree and shrub forests shows an S-shaped change, indicating a significant layered utilization of soil moisture by heavy rain. The spatial variation of soil moisture and its response to rainfall in different vegetation types are influenced by the interception of vegetation canopy on precipitation redistribution. Principal component analysis between soil moisture and environmental factors shows that canopy closure, leaf area index, soil bulk density between 150-200 cm, fine root biomass density, root surface area density, root length density, and specific root length are significant factors reflecting soil moisture in the study area (P ＜ 0.05). Research has shown that there are significant differences in soil moisture content of vegetation with different rainfall intensities. The establishment of tree and shrub vegetation on sandy land in alpine and semi-arid regions can enhance the water storage capacity of deep soil layers; The results can provide scientific basis for the restoration of sandy land and the prevention and control of soil erosion.