中文摘要：

土壤水热状况变化是退化草地土壤的主要特征,对退化草地生态系统具有重要的影响。研究青藏高原退化草地的土壤温湿度变化规律,可以对高原草地在各季节、各时段的土壤温度和湿度变化进行动态预测,同时,对于退化草地的恢复和改善环境具有指导意义。选择青藏高原玛多地区典型退化草地,利用一年的观测数据,计算土壤温度、土壤湿度及土壤热通量的季节变化和年变化特征,分析土壤温度和湿度及热通量之间的相互关系。结果表明：在季节变化上,土壤温度和湿度在夏季均为最大值,土壤温度在各季节的变化趋势较一致,土壤热通量变化幅度比温度和湿度大,日振幅达到102 W.m-2;在年变化上,土壤湿度在6月出现最大值,12月出现最小值,极值年较差为12.6%。春季和夏季的土壤热通量均大于0 W.m-2,冬季均小于0 W.m-2。青藏高原退化草地土壤温湿度及热通量存在明显的季节变化和年变化特征,就土壤湿度而言,夏季是高原的湿润期,春季和秋季为干旱期。青藏高原地区土壤从11月开始冻结,次年4月开始解冻。土壤热通量在春季和夏季均为正值,说明这一时段热量由大气向土壤传递;冬季则相反,热量由土壤向大气传递。整体而言,土壤温度和湿度及土壤热通量之间的关系呈显著正相关。

英文摘要：

Soil moisture and heat conditions are the main factors affecting steppe degeneration and steppe ecosystem.The seasonal dynamic changes of soil temperature and soil moisture content in a degenerated steppe in the Qinghai-Tibet Plateau can be predicted,which is of the guiding significance for regenerating and improving the degenerated ecology and environment.In this study,the 1-year data observed in a typical degenerated steppe in Maduo County in the Qinghai-Tibet Plateau were used to analyze the relationships between soil temperature,moisture content and heat flux and their seasonal and annual variation.The results show that the values of soil temperature and moisture content were the highest in summer,there was a consistent trend in seasonal change of soil temperature,the change range of soil heat flux was higher than that of soil temperature and moisture content,and its daily fluctuation was 102 W·m-2.The maximum and minimum values of soil moisture content occurred in June and December separately,and the annual range of the extreme value was 12.6%.Soil heat flux was higher than 0 W·m-2 in spring and summer but lower than this value in winter.There were the significant seasonal and annual changes of soil temperature,moisture content and heat flux,and the soil moisture content was high in summer but low in sparing and autumn.Soil in the Qinghai-Tibet Plateau froze in November and thawed in April.The value of soil heat flux in spring and summer was positive,which reveals that heat transferred from air to soil in these two seasons,and contrarily,heat transferred from soil to air in winter.Holistically,there were the significant positive correlations between soil temperature,moisture content and heat flux.