Effects of artificial grasslands on the freeze-thaw process of black soil beaches in permafrost regions

Artificial grasslands have been widely used as an important measure to restore degraded grassland on black soil beaches. To date, studies have mainly assessed the effects of artificial grasslands on vegetation characteristics and soil carbon sequestration. However, few studies have examined the effects of artificial grasslands on soil freeze-thaw processes. In this study, the “black soil beach” type degraded grasslands and artificial grassland areas in the permafrost regions of Shule River headwaters in the northeastern margin of the Qinghai-Tibet Plateau and the western part of Qilian Mountain were considered as research objects and analyzed for the measured data of soil temperature, moisture content, and salt content in the “black soil beach” and artificial grassland areas. The results showed the following: 1) Compared with the “black soil beach”, artificial grassland areas have higher soil temperatures in winter and are less affected by temperature fluctuations. Their overall soil moisture content are slightly higher than those in the “black soil beach” and are less affected by precipitation. The soil salinity contents in artificial grassland areas are lower than those of the “black soil beach”, most obviously in summer and autumn. These results are in line with the expectation that artificial grassland areas have a better thermal insulation effect and salinization resistance than that of the “black soil beach”. 2) In artificial grasslands, soil freezing days were prolonged, whereas the thawing and freeze-thaw days were shortened, indicating that artificial grasslands could effectively reduce the frequency of soil freeze-thaw processes and weaken freeze-thaw erosion. These results provide indications for restoring and protecting the ecological environment in alpine regions.