Recent expansion of talus slopes in the northern Taihang Mountain Range, China: an example from the Xiaowutai Region

Talus slopes play an important role in landscape evolution in some mid-altitude mountains. In this study, we analyzed talus slope activity on Xiaowutai Mountain in the Northern Taihang Mountain Belt, China, using a combination of aerial map interpretation, topographic analysis, field investigation, and climate monitoring. Most of the identified talus slopes were located in the elevation range 1501–2882 m, on south-facing slopes with a gradient of 20.1–45°, and in areas with sparse vegetation and underlying rhyolite geology. Their number and area significantly increased between 2003 and 2017 in association with a warming climate. The annual change in the area covered by talus slopes was positively and negatively correlated to thawing and freezing indexes, respectively, with the largest coverage increase recorded in 2016. Furthermore, the average area of high-roughness talus slopes increased more between 2015 and 2016 compared to low-roughness talus slopes. We show that surface runoff is the primary factor driving talus slope expansion in this area, which is secondary to freeze-thaw cycling. These results provide a new understanding of the development of talus slopes in similar mid-altitude regions in comparison to alpine and polar areas, where ice melting is considered the dominant formation mechanism.