Spring snowmelt affects changes of alpine tundra vegetation in Changbai Mountains

Climate and environmental changes have caused changes in alpine tundra worldwide in recent decades. However, the roles of snow cover on tundra vegetation change remain less studied. There were obvious changes of alpine tundra vegetation, such as herbaceous encroachment and shrub expansion reported in Changbai Mountains in recent decades. This study investigates the relationship between snow cover and vegetation change (1988-2017) in alpine tundra of the Changbai Mountains by analysing the hydrological distribution of spring snowmelt in the tundra. We mapped the wet snow extent using Sentinel-1 synthetic aperture radar (SAR) spaceborne data and estimated the snow water equivalent (SWE). We proposed a measure of relative water accumulation (RWA), which was determined by both rainfall and SWE, to represent water flowing through each pixel. We found strong correlations between RWA and vegetation change in different mountain aspects. Spring snowmelt leads to inter-mountain aspect differences in hydrological distribution, with the western aspect showing a significant higher RWA than the eastern and northern aspects, which could attribute to the greater vegetation change in the western mountain aspect. Our results suggest that the distribution of snow in alpine tundra and the different mountain aspects hydrological conditions have important implications for the study of vegetation change in alpine tundra.