藏北高寒草原土壤温度变化与冻融特征

Soil Temperature Variation and Thaw-freezing Cycle in the Alpine Cold Steppe,Northern Tibetan Plateau

冻融是藏北高寒区重要的自然环境特征和表生过程,冻融过程中土壤水分和热量迁移及其温湿度的时空分布特征对生态系统具有重要的意义。利用青藏高原申扎站高分辨土壤温度数据资料,对土壤温度不同时间尺度的变化特征,特别是冻融过程中土壤温度日和季节尺度变化特征进行分析。结果表明:观测期内,日尺度和月尺度上气温与土壤温度整体变化趋势具有一致性,但土壤温度变化相对缓和,且随着深度的增加,这种平缓趋势和时滞愈加明显;土壤温度冬春季变幅剧烈,反应了冻融过程对土壤温度的显著调节作用;小时尺度上,土壤温度昼夜变化过程大致呈现正弦波型,随深度增加,振幅减小,峰谷变化相位滞后延长。研究可为该区域生态、土壤、植被、微气候、微地貌等地表原位地理环境过程研究提供相关依据。

Thaw-freezing cycle is the primary environment character and land surface processes in the alpine cold region, such as Northern Tibetan Plateau. The variation of soil temperature and soil moisture underground during the thaw-freezing processes are of great significance to ecosystems. The soil temperature, the basic effecting factor of the thaw-freezing cycle, was studied at Xainza at hourly to monthly scale, to offer references for the scientific re- search such as ecology, soil, land cover, microclimate, microtopography on the Northern Tibetan Plateau. The re- sults showed that the variation of soil temperature was similar to that of air temperature at daily to monthly scale for their robust correlation, while the soil temperature varied in a more slowly style with time-delays, which enhanced with the depth. Also, the soil temperature got strong coefficient of variation （CV） values during thaw phrase, indic- ting the effect of freezing-thawing processes on temperature. At hourly scale, the soil temperature varied in sine waves style, with the waves smoothed and delayed gradually for the increase of depth.