三江源区不同退化程度高寒草甸表土层的土壤水分变化特征

Variations of Moisture in Surface Soil of Alpine Meadow with Different Degradation Degrees in the Three-River Source Region

土壤水分是影响青藏高原高寒草甸生态过程和生态承载能力关键因素之一,掌握其变化特征对于高寒地区生态保护和修复具有重要意义。基于HOBO土壤温湿度仪器监测数据,分析2019年8月至2020年8月三江源区不同退化程度(未退化(ND)、轻中度退化(LMD),重度退化(HD))下高寒草甸表土层土壤3个层级L1(0—5 cm)、L2(5—15 cm)、L3(15—30 cm)土壤水分变化特征。结果表明:(1)不同退化程度下土壤含水量季节差异明显。高值区主要分布在夏季,低值区分布在冬春季。不同退化程度下土壤表层含水量年内均值大小依次为LMD(0.320 cm^(3)/cm^(3))、ND(0.284 cm^(3)/cm^(3))和HD(0.211 cm^(3)/cm^(3))。(2)夏季降水事件结束后,土壤含水量24 h后开始明显减小,其中,L1层变化幅度最大,L3层变化幅度最小。(3)ND和LMD高寒草甸0—5 cm土层,HD高寒草甸5—15 cm土层对应的是相对较高含水层,这是由于土壤含水量与土壤容重呈显著负相关,与C/N、有机碳呈显著正相关。

Soil moisture is one of the key factors affecting the ecological processes and ecological carrying capacity of alpine meadows in the Qinghai-Tibet Plateau.Mastering its change characteristics is of great significance for ecological protection and restoration in alpine region.Based on the soil moisture data monitored by hobo soil temperature and humidity instrument(HOBO Data Loggers-Onset Corporation of USA),soil moisture change characteristics during August 2019 and August 2020 of three layers L1(0—5 cm),L2(5—15 cm)and L3(15—30 cm)of alpine meadow topsoil under different degradation stage sites,which were non-degradation(ND),light to moderate degradation(LMD),highly degradation(HD),in the Three-River Source Region were analyzed.The results showed that:(1)There were significant seasonal variations in soil water content under different degradation stages.The high values mainly distributed in summer,while the low values distributed in winter and spring.The intra-annual mean values of topsoil water content under different degradation types followed the order of LMD(0.320 cm^(3)/cm^(3))>ND(0.284 cm^(3)/cm^(3))>HD(0.211 cm^(3)/cm^(3)).(2)After continuous rainfall in summer,the soil water content began to decrease significantly after 24 hours.Among them,the change range of L1 layer was the largest and that of L3 layer was the smallest.(3)The soil depth of 0—5 cm in ND and LMD alpine meadows,and the 5—15 cm of HD alpine meadows corresponded to a higher water content layer,because that the soil water content was significantly negatively correlated to soil water content and soil capacity,and significantly positively correlated to C/N and organic carbon.