Spatial variability and its main controlling factors of the permafrost soil-moisture on the northern-slope of Bayan Har Mountains in Qinghai-Tibet Plateau

摘要

The soil moisture movement is an important carrier of material cycle and energy flow among the various geo-spheres in the cold regions.Thus,this research takes the north slope of Bayan Har Mountains in Qinghai-Tibet Plateau as a case study.The present study firstly investigates the change of permafrost moisture in different slope positions and depths.Based on this investigation,this article attempts to investigate the spatial variability of permafrost moisture and identifies the key influence factors in different terrain conditions.The method of classification and regression tree (CART) is adopted to identify the main controlling factors influencing the soil moisture movement.The relationships between soil moisture and environmental factors are revealed by the use of the method of canonical correspondence analysis (CCA).The results show that:1) Due to the terrain slope and the freezing-thawing process,the horizontal flow weakens in the freezing period.The vertical migration of the soil moisture movement strengthens.It will lead to that the soil-moisture content in the up-slope is higher than that in the down-slope.The conclusion is contrary during the melting period.2) Elevation,soil texture,soil temperature and vegetation coverage are the main environmental factors which affect the slopepermafrost soil-moisture.3) Slope,elevation and vegetation coverage are the main factors that affect the slope-permafrost soil-moisture at the shallow depth of 0-20 cm.It is complex at the middle and lower depth.