Effects of cold-season snow on late warm-season vegetation on the Tibetan Plateau

Studying the effects of cold-season snow on warm-season vegetation and understanding the underlying mechanisms may help conserving ecosystems and implementing effective steps to counteract climate change on the Tibetan Plateau (TP). Using regression, correlation, and composition analysis as well as data on fractional snow cover (FSC), normalized difference vegetation index (NDVI), National centers for Environmental Prediction (NCEP) and climate Prediction Center Merged Analysis of Precipitation (CMAP), the relationships between cold-season snow and warm-season vegetation on the TP were investigated. The results showed that when cold-season snow increased, warm-season vegetation also increased on the TP, and vice versa. This relationship is supported by background atmospheric circulation. When the amount of snow in the cold season is untypically large, the eastern Asia summer monsoon weakens, and the Pacific subtropical high increases, moves westward and affects the eastern TP during the warm season. Such an atypical high during the warm season results in higher surface temperatures, snow melting, increased soil moisture, increased solar radiation, and decreased precipitation, the first four phenomenona of which favor vegetation growth. Especially, melting snow provides considerable amounts of water to the soil, which favors vegetation rejuvenation and early growth. Precipitation is the main source of soil water, and it is typically abundant and meets the requirements of vegetation growth during warm season; however, NDVI is highest during the warm season, and excessive precipitation may result in reduced vegetation growth, thus a slight decrease in precipitation may promote vegetation growth.