Change of snow cover and its impact on alpine vegetation in the source regions of large rivers on the Qinghai-Tibetan Plateau, China

Based on a Normalized Difference Vegetation Index (NDVI) and remote sensing data of snow cover, we analyzed the variation in NDVI in relation to trends in snow cover and vegetation of the source regions of large rivers on the Qinghai-Tibetan Plateau. We then calculated the relationship between snow cover duration, snow depth, and NDVI to reveal the effect of snow cover change on vegetation growth on a regional scale. The results show that both snow depth and duration tend to reduce gradually from northeast to southwest on the Qinghai-Tibetan Plateau. Furthermore, snow cover duration (snow depth > 0 cm) has high interannual fluctuation and generally shows an increasing trend (P < 0.01) from 1980 to 2004. The interannual fluctuations of the duration of days with snow depth >= 5 cm as well as the maximum and average snow depth are also quite high, but they generally show insignificant tendencies (P > 0.05) from 1980 to 2004. The snow cover characteristics (duration and depth) are insignificantly correlated to annual maximum NDVI. However, a significant positive correlation (P < 0.05) is observed between snow cover duration (snow depth > 0 cm) and the NDVI values of both April and July, and an obvious negative correlation (P < 0.05) is observed between snow depth and the NDVI value in October across all source regions from 1981 to 2004. In the study area, increasing snow depth and the prolongation of the duration of snow cover have adverse effects on vegetation growth the following year. The melting of snow brings increasing effects to the NDVI value in the spring.