青藏高原高寒草甸土壤水分运移机制

A study of soil moisture migration mechanism of alpine meadow in the Tibetan Plateau

查明青藏高原高寒草甸区土壤水分运移机制,对正确理解土壤水分迁移过程、提高高寒草甸重建效率具有重要指导意义。通过开展土壤剖面负压、地温观测等原位试验,结合气象资料,对土壤剖面地温、含水率及总水头特征进行分析。结果表明,土壤的冻结期起始于10月,解冻期起始于4月;地温最高值出现在植物生长旺盛期8月,最低值出现在1月;1～3月土壤水分呈固态,6～10月土壤水分呈液态,处于稳定变化阶段,4～5月、11～12月土壤水分呈固液转化态,含水率变化幅度较大,处于过渡阶段。随着气温升高及降水量增加,6～8月水热同季有利于高寒草甸生长,属于高寒草甸主要生长阶段;春季土层由表及深土壤解冻,冻土层滞水性能保障了返青期春旱牧草生长的水分需求;深秋季节的由表及深的土壤冻结,深层土壤水分随水汽发生的表聚作用保障了牧草生长的水分需求,也是高原生态系统能够维持稳定的原因之一。

The alpine meadow soil water for sustaining the succession of vegetation ecosystem benign role lies in finding out the alpine meadow area soil moisture migration mechanism,the correct understanding of alpine meadow soil moisture migration process;the improvement of the reconstruction efficiency has important guiding significance.In this paper,based on in situ test of soil profile negative pressure and ground temperature observation,combined with meteorological data,the authors analyzed soil profile temperature,moisture content and total head characteristics.The results show that the freezing period begins in October,and the thawing period begins in April.At the highest temperature,the plant growth period is in August,and the lowest value appears in January.Soil moisture is solid from January1to March;from June to October soil water is liquid,belonging to stable phase change;from April to May and from November to December soil moisture is in solid and liquid state,and the moisture content change is bigger,belonging to the excessive stage.With the increase of temperature and the precipitation,the same season in June and August is favorable for the growth of alpine meadow,which belongs to the main growth stage of alpine meadow.In spring,the soil is thawed at the surface and the depth,and the stagnant water performance of the frozen soil ensures the moisture demand of the spring drought and herbage growth.In the late autumn season,the surface and deep soil are frozen,and the moisture content of the deep soil water with the water vapor in the soil protects the moisture demand of the grass growing.This is one of the reasons that the plateau ecosystem can be stable.