东北半干旱区退化草地土壤温度的日、季变化特征

Diurnal and Seasonal Variations of the Soil Temperature of Degraded-Grassland over Semi-Arid Area in Northeast China

在国家基础研究发展规划项目（973）“我国生存环境演变和北方干旱化趋势预测研究”支持下，吉林通榆“干旱化和有序人类活动”长期观测实验站于2002年10月建成并正式开始观测，该站也是国际协同加强观测计划（CEOP）观测网中36个地面站之一。本文利用2002年10月2005年12月高密度连续观测资料，对退化草地下垫面土壤温度变化特征进行了分析。发现在东北半干旱地区，退化草地0～10cm深处土壤温度日变化明显，20cm处日变化较弱（冬季无明显日变化），50cm以下无日变化；土壤温度0～80cm存在明显的年变化周期，20cm以下位相滞后明显，土壤垂直温度梯度经历一个负→转换期→正→转换期→负的年循环。土壤冻结期约96天。太阳辐射是影响土壤温度长期变化的主要因素；土壤表层温度、湿度的日变化对降水事件的响应因降水强度、时间等的不同而不同。太阳辐射是影响土壤温度长期变化的主要因素；土壤温度对降水事件的响应近似一渐变过程，而土壤湿度相对是一快速的跃变响应过程。

Under the support of the national key basic research development program ＂The predictive study of aridification in northern China in association with life-supporting environment changes＂, the longterm monitoring experiment on aridification and the ordered human activity has been set up at Tongyu in semi-arid area, Northeast China since October 2002. It is also one of the 36 reference sites on energy and water flux cycle between the land surface and the atmosphere of Coordinate Enhanced Observation Period （CEOP）. In this paper, the diurnal and seasonal variations of the soil temperature were analyzed by using the observation data collected during the period of October 2002-December 2005. The results indicate that over the degraded grassland in semi-arid area in northeast China, the seasonal variation of soil temperature above 80 cm is evident and the phase variation of soil temperature below 20 cm is apparently lagged. The variation of the vertical gradient of the soil temperature has seasonal cycle. There is an evident diurnal variation of soil temperature in the near surface layer above 10 cm, while the diurnal variation of soil temperature at 20 cm is not clear, and the soil temperature below 50 cm just has seasonal course. The vertical gradient of the diurnal cycle of the soil temperature exists a period from upward to downward around one year cycle just except in November and December. The period of soil freezing is about ninety-six days. The net radiation is a dominating factor on the long variation of the soil temperature. The impact of soil temperature diurnal variation to precipitation is different from that of soil moisture because of intensity and time of precipitation. The net radiation is a dominating factor on the long variation of the soil temperature. The impact of soil temperature to precipitation is nearly a gradual change process; on the contrary, the impact of soil moisture to precipitation is a nearly a sudden change process.