Soil water content in permafrost regions exhibited smaller interannual changes than non-permafrost regions during 1986–2016 on the Qinghai-Tibetan Plateau

Abstract

Permafrost is an important factor affecting soil hydrology in cold regions, while the effects of permafrost on temporal changes in soil water content largely remain unknown. Here, based on the calibrated Climate Change Initiative (CCI) soil moisture products using field observation soil water data at 5 cm depth from 8 representative sites, we examined changing trends of climate conditions and soil water contents during 1986–2016 between the permafrost and permafrost-free sites on the Qinghai-Tibetan Plateau (QTP). We found that all the sites have been experienced continuous warming during this period. Soil water contents showed significant increasing or decreasing trends at three of the four permafrost-free sites, but there were no significant increasing or decreasing changes at all the four permafrost sites. In addition, the Mann-Kendall (M−K) test showed that there were 2 change-points in soil water content for the sites with the active layer thickness was about 2 m, while the sites with active layer thickness larger than 3 m and permafrost-free sites showed 3–5 change-points, indicating that the soil water contents in areas with shallower active layer showed smaller changes. The different changing trends and change-points between permafrost and permafrost-free sites were associated with the existence of permafrost and active layer thickness. Although soil water contents can be affected by many factors, our results suggested that permafrost existence can affect interannual changes in soil water contents, and permafrost degradation including increasing active layer thickness and disappearance of permafrost may decrease ecosystem resilience in the face of climate change.