Desertification Caused by Embankment Construction in Permafrost Environment on the Qinghai-Tibetan Plateau

Desertification is a process of land degradation embodied in soil water reduction, soil deterioration and vegetation degradation. As an important factor to evaluate the desertification degree, the water content of shallow soil will infiltrate downward when permafrost degrades on the Qinghai-Tibet Plateau (QTP). With the development of transportation facilities on the QTP, embankment construction, which will directly change the surface cover and reduces the water content of shallow soil by degrading the permafrost. In this study, an embankment construction in the permafrost region of the QTP was selected and a hydro-thermo-vapor coupling model for the embankment-permafrost system was established. The mechanism and process of desertification caused by permafrost degradation were analyzed by the variations of geotemperature and soil water. The results show that: (1) embankment construction has increased the heat flowing into the ground, warmed the underlying permafrost and deepened the permafrost table by more than 10 m during 50 years. (2) Accompanied with the permafrost degradation, the shallow soil water migrates downward and accumulates near the deepening permafrost table, showing a funnel-shaped distribution. The average water content of shallow soil under the changed surface has decreased by 5-6% during 50 years, indicating the intensification of desertification. (3) Desertification and permafrost degradation on the QTP is interconnected by the redistribution of soil water. Desertification and permafrost degradation are the mutual promotion process on the QTP.