Relationship between vegetation phenology and snow cover changes during 2001–2018 in the Qilian Mountains

Abstract

Vegetation phenology has a profound impact on soil and water conservation and biogeochemical cycles, while its relationship with snow parameters has not been well addressed for parts of the Qinghai-Tibet Plateau (QTP). In this study, we identified the variations in vegetation phenology and showed its correlation with snow cover for varied underlying conditions and elevation zones in the Qilian Mountains (QLMs) in northern parts of the QTP based on the MODIS NDVI product (MOD13Q1) and snow cover area dataset. Partial correlation analysis demonstrated that end of snow cover (SCE) is negatively correlated to the start of the growing season (SOS) in relatively higher mountains, but it is positively correlated to SOS around Qinghai Lake and eastern Lenglongling Mountain. On the contrary, the snow cover duration (SCD) is positively correlated with the length of the growing season (LOS) in most parts of the QLMs, but it is negatively correlated with LOS in Lenglongling Mountain and around Qinghai Lake. The influences of snow cover on vegetation phenology depend on the underlying surface conditions which are evidenced by a stronger correlation between the start of snow cover and SCD and SOS of grassland than that of brushland, cropland, and woodland, while the influences of SCE on vegetation phenology are weak. The correlation between snow parameters and vegetation phenological events is significant on the south slopes>30 °C with elevation zones of 3500–4200 m asl and < 2800 m asl. The results of the study are significant for facilitating research in the management of the cold region eco-environment in the QLMs.