中文摘要：

浅层土壤温度的变化可以指示活动层厚度变化。利用青藏高原及毗邻地区74个站1977—2006年近30年的土壤温度资料,研究了青藏高原及毗邻地区土壤热状况。结果表明,自1977年的近30年来,5cm土壤负积温绝对值有减小的趋势,在高原的不同区域减小的幅度不同,对整个研究区域而言,负积温绝对值每10年降低了35℃;近30年来研究区内土壤的最大冻结深度呈现减薄的趋势;冻结期间（冷季）高原腹地负积温变化幅度要比边缘地区大,而在一个完整的冻融循环过程中,高原腹地相对于边缘地区稳定;近30年来高原地区冻融强度（FTI）呈现增大的趋势,这在某种程度上表明高原多年冻土区冻土的稳定性发生了变化;纬度及海拔对FTI值的影响较大,当海拔低于4000m时,33°N南北两区域FTI值随海拔升高的减小率不同,南部减小的量是北部的2.5倍,海拔高于4000m时,FTI值受纬度影响相对减弱。

英文摘要：

Changes of shallow layer ground temperature can indicate the changes in active layer thickness. The soil thermal regime of the active layer was analyzed using the ground temperature data from 1977 to 2006 collected at 74 weather stations on the Qinghai-Tibet Plateau （QTP） and its adjacent areas. The results indicate that in the last 30 years the negative accumulated temperature at 5 cm depth below surface showed an increasing trend, but had different increment magnitudes in different regions. For the entire study area, the negative accumulated temperature increased 35 ~C per decade. The freezing thickness of active layer showed a decreasing trend in the past 30 years in the regions. During the freezing period （cold season） the magnitude change of negative accumulated temperature was greater in the hinterland of QTP than in its peripheral areas, but it was more stably in a complete freeze-thaw cycle in the hinterland than in the peripheral areas. In the past 30 years, the values of freeze-thaw intensity （FTI） exhibited an increasing trend, which indicates that the stability of frozen ground has changed to some extent in the permafrost regions. In the QTP, latitude and altitude had a great impact on FTI. While altitude is below 4000 m, the decreasing rate of FTI with increase in altitude was different between the regions south and north of 33°N. The value in the south region was 2.5 times of that in the north region. While the altitude is above 4000 m, its impact on FTI values reduced relatively.