根据2018—2020年青海湖流域高寒草甸野外定点监测的温度、降水、土壤水热数据，分析了高寒草甸生态系统土壤冻融特征以及不同冻融阶段土壤温度、水分的日变化和季节动态过程。结果表明：①基于土壤温度变化特征分析，可将冻融循环过程划分为始冻期、完全冻结期、解冻期和完全融化期。各阶段持续的天数长短依次为：完全融化期>完全冻结期>解冻期>始冻期。从表层到深层土壤，完全融化天数持续增大，完全冻结天数趋于减小，0~180 cm土层完全融化期持续天数超过半年以上。②冻土表现出单向冻结、双向融化的规律，土壤融化速率（5.45 cm/d）快于土壤冻结速率（2 cm/d）。整个冻融过程，不同深度土壤水分的变化比温度的变化更复杂。③随着冻融循环过程，土壤温湿度呈现出周期性的季节变动特征。土壤温湿度日变化具有一致性，表层日较差大，随着深度的增加，日较差变小并趋于稳定。土壤剖面的结构特征对土壤水分异质性分布具有较强的解释性。

Based on the temperature, precipitation, and soil moisture and temperature data of the alpine meadows in the Qinghai Lake Watershed from 2018 to 2020, the characteristics of soil freezing and thawing in the alpine meadow ecosystem and the daily changes and seasonal dynamics of soil temperature and moisture in different freezing and thawing stages were analyzed. The results showed that:1) Based on the analysis of the characteristics of soil temperature changes, the freeze-thaw cycle process could be divided into the initial freezing period, the complete freezing period, the thawing period and the complete thawing period. The duration of each stage was as follows:complete thawing period>complete freezing period>thawing period>initial freezing period. From surface to deep soil, the number of days of complete melting continued to increase, and the number of days of complete freezing tended to decrease. The period of complete melting of 0-180 cm soil layer lasted for more than half a year. 2) Frozen soil showed the law of one-way freezing and two-way melting. The soil melting rate (5.45 cm/d) was faster than the soil freezing rate (2 cm/d). Throughout the freeze-thaw process, the changes in soil moisture at different depths were more complex than changes in temperature. 3) With the freeze-thaw cycle process, soil temperature and moisture showed periodic seasonal changes. The diurnal variation of soil temperature and moisture was consistent, and the surface layer had a large diurnal range. As the depth increases, the diurnal range became smaller and tended to be stable. The structural characteristics of soil profile had a strong explanatory effect on the heterogeneous distribution of soil moisture.

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国家自然科学基金项目（41730854）资助。