Abstract
As the roof of the world, the Mt. Qomolangma National Nature Reserve and adjacent regions have a fragile environment and are very sensitive to global climate change. Based on the MODIS and SPOT remote sensing data during 2000–2018, we aimed to explore the change trend and driving factors of grassland in this area under the dual influence of climate change and human activities. Here, temperature and precipitation data were enrolled as the main indicators of climate change, while the number of livestock at the end of the year was regarded as the key indicator of grazing. The results showed that: (1) during 2000–2018, the grassland NDVI reflected an overall increasing trend, and the impact of precipitation was more significant than those of temperature and grazing at both pixel and county levels; (2) probably due to the large population and high grazing intensity, the grassland NDVI in Tingri County was controlled by both precipitation and grazing. In general, precipitation exerts a greater impact on the NDVI changes since this region is characterized by arid and semiarid climates. In some areas, vegetation growth is simultaneously affected by both grazing and climate factors due to the relatively greater pressure of grazing. In the context of future warming, control of the number of tourists for Mt. Qomolangma, as well as that of livestock in Tingri County, will help improve sustainability development and to reduce the adverse effects of grassland degradation.
Highlights
State Key Laboratory of Tibetan Plateau Earth System, Resources and Environment (TPESRE), Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100101, China; Motuo Observation and Research Center for Earth Landscape and Earth System, Chinese Academy of Sciences, Linzhi 860712, China
Synthesizing the population and grazing intensity data of the seven counties in the study area during the past 20 years, we found that both data were significantly correlated with each other (Figure 8b), i.e., the variation in population density at the county level largely reflected that of the grazing in population density at the county level largely reflected that of the grazing intensity
We found that the normalized difference vegetation index (NDVI) showed an overall increasing trend during 2000
Summary
A large number of studies have proven that global climate change is an important driving factor for changes in terrestrial vegetation in recent decades [1–3]. The sensitivity of vegetation productivity to temperature changes at the beginning of this century has declined, and climate warming during nongrowing seasons is considered as one of the main reasons [7]. Another study found that temperature increases are likely to affect the plant growth of alpine grassland by changing the forms of precipitation at the beginning of the growing season [9]. With temperature, the changes in precipitation are not necessarily the main limiting factor for the variations in the normalized difference vegetation index (NDVI) on the Tibetan Plateau [10], changes in moisture caused by temperature (such as increased evaporation) are likely to affect vegetation growth. To explore the impact of climate change on alpine grasslands, we need to fully consider the temporal and spatial changes in temperature and precipitation
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