祁连山区不同土地覆被类型下土壤水分变异特征

Variations of Soil Moisture Under Different Land Use and Land Cover Types in the Qilian Mountain,China

结合土壤、植被、地形等要素,建立黑河上游土壤水文观测体系,收集代表黑河上游区域特征的36个定位观测点土壤水分数据和12个气象站的降水数据,采用经典统计方法揭示祁连山区区域尺度上7种土地覆被类型下的土壤水分变异特征。结果表明,降水和植被特征是影响生长期土壤水分的主要因素。降水量大的土地覆被类型上土壤水分值较高。同时土壤水分值越低,降水补给和蒸散发消耗所引起的相对波动就越大,导致其变异性越大。由于植被根系对土壤水分的显著影响,高盖度草地、低盖度草地的土壤水分值在剖面各层变化不大,而农田、草甸、灌丛、林地和裸地土壤水分值随深度变化较明显。草甸、灌丛、裸地土壤水分整体均在夏季最高、秋季次之、春季最低。农田和高盖度草地土壤水分均呈现秋季最高、夏季次之、春季最低。土壤水分变异程度除灌丛外,存在春季变异最大,夏季次之和秋季最小的规律。降水是导致土壤水分值和变异系数在夏、秋季变化的主要因素,而土壤冻融过程则是导致其在春季变化的主要因素。总而言之,祁连山区土壤水分具有明显的空间分布差异与季节变化特征,与不同土地覆被类型的降水条件、植被特性和人工影响都有着密切的关系。

Soil moisture links the atmospheric precipitation,surface water,and groundwater together,its spatiotemporal variability influences both ecological and hydrological processes.Considering soil properties,vegetation,terrain,and other factors,we established the soil hydrological observation system with 36in-situ soil moisture observation stations in the Qilian Mountain,Northwest China.We analyzed the variability of soil moisture in the study area by using the classical statistical methods.Results show that precipitation and vegetation characteristics are the main factors affecting the variability of soil moisture.Large precipitation on land cover types led to high soil moisture.Lower soil moisture resulted in higher volatility of evapotranspiration and precipitation recharge,leading to the greater variability.Due to the significant influence of vegetation roots on soil moisture,soil moisture in high cover grassland and low cover grassland showed little change along the soil profile,while soil moisture in the farmland,meadows,shrubs,forestland and bare land showed sharp change with the soil depth.For meadows,shrubs,bare land,the soil moisture was highest in summer and autumn,it was minimal in spring.Soil moisture contents in farmland and high coverage grassland were the highest in fall,followed by summer,soil moisture content was the lowest in spring.In addition to the shrubs,soil moisture variation extent was the largest in spring,followed by summer,and it was minimum in autumn.Precipitation was the main factor affecting the coefficient of variation of soil moisture in the summer and autumn while soil freezing and thawingprocess was the major factor controlling the soil moisture in spring.