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Abstract:
The continued climate warming has increased the drought risk for ecosystems in many areas of the globe. However, in cold regions, climate warming brings a more complicated impact on drought and ecosystems. A warmer climate and shorter snow duration may extend vegetation phenology and increase productivity, while increased evaporative demand may aggravate the vulnerability of the ecosystem to drought. In this study, we select the Qilian Mountains (QLMs) in northwestern China as a case study area, which has experienced intense climate change. We utilized a long-term and downscaled normalized difference vegetation index (NDVI) product to investigate how climate change, drought, and snow variability jointly affect the fine-scale greenness dynamics of different vegetation types. Results suggest that most areas in the QLMs experienced a greening trend while the western part displayed a browning. The grass and shrub demonstrated a decreased sensitivity to drought over the medium altitudes but increased drought sensitivity at the lower and upper altitudes. The broadleaf forests showed intensifying drought sensitivity at all elevations. Coniferous forests and alpine meadows respectively displayed decreasing and increasing trends of sensitivity to drought along elevations. The increased vulnerability of vegetation to drought over the lowest and highest elevations is likely attributed to a combination of the fastest warming and mildest wetting trends. Snow cover shows a significant effect in maintaining vegetation growth through increasing soil moisture in dry periods. These findings provide insights into how these cold-region vegetation communities may respond to drought under a warmer and snow-less climate in the future.
