Abstract
Vegetation dynamics under a warming climate in the source region of the Three Rivers (SRTR) and its ecological impacts are a source of serious concern. In this study, we investigated the spatial and temporal variations of normalized difference vegetation index during the growing season (NDVIgr) and the start of the vegetation growing season (SOS) for six ecosystems. We examined the relationships between vegetation parameters, air temperature, precipitation and land management using residual trend method from 1982 to 2015. The NDVIgr increased at a rate of 0.0061/10a, and SOS advanced by 0.96 d/10a during the study period. The NDVIgr increased for the all six vegetation ecosystem from 1982 to 2015. The SOS showed advancing trend for the vegetation types for meadow (0.1236 d/a) and steppe (0.3480 d/a), but showing delaying trends for forest, shrub, barren land and alpine vegetation. The results of the correlation analysis indicate an increase in the air temperature in the SRTR is the main factor explaining increases in the NDVI and advancement of the SOS. In general, awarming-wetting climate and reasonable human activities had positive effects on vegetation growth, while the positive impact of human activities was weaker than that of climatic factors. This study provides a necessary basis for research on and the prediction of vegetation changes and their response to the climate warming of the SRTR in the Qinghai-Tibet Plateau (QTP).
Highlights
The Yellow River, Yangtze River and Lantsang River originate in the Qinghai-Tibet Plateau (QTP), which is a cold and arid region with a fragile ecosystem (Wang et al, 2017)
This study provides a necessary basis for research on and the prediction of vegetation changes and their response to the climate warming of the source region of the Three Rivers (SRTR) in the Qinghai-Tibet Plateau (QTP)
The most significant increase in the NDVI for the SRTR occurred in the source region of the Yellow River which located in the eastern SRTR
Summary
The Yellow River, Yangtze River and Lantsang River originate in the Qinghai-Tibet Plateau (QTP), which is a cold and arid region with a fragile ecosystem (Wang et al, 2017). Some studies have reported that pronounced soil temperatures combined with the degradation of frozen grounds may promote vegetation growth in cold regions (Myneni et al, 1997; Zhong et al, 2010; Xu et al, 2011). These studies have stressed that the increase in temperature may mitigate the low-temperature stress of alpine vegetation and promote the nutrient cycle (Zhou et al, 2015). It remains unclear whether a warming climate has positive or negative effects on vegetation growth
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