Abstract
Grasslands occupy nearly three quarters of the land surface of the Qinghai-Tibet plateau (QTP) and play a critical role in regulating the ecological functions of the QTP. Ongoing climate change and human interference have greatly affected grasslands on the QTP. Differentiating human-induced and climate-driven vegetation changes is vital for both ecological understanding and the management of husbandry. In this study, we employed statistical analysis of annual records, various sources of remote sensing data, and an ecosystem process model to calculate the relative contribution of climate and human activities to vegetation vigor on the QTP. The temperature, precipitation and the intensity and spatial pattern of livestock grazing differed between the periods prior to and after the year 2000, which led to different vegetation dynamics. Overall, increased temperature and enhanced precipitation favored vegetation growth. However, their combined effects exhibited strong spatial heterogeneity. Specifically, increased temperature restrained vegetation growth in dry steppe regions during a period of slightly increasing precipitation from 1986 to 2000 and in meadow regions during a period of precipitation decline during 2000–2011, thereby making precipitation a dominant factor. An increase in precipitation tended to enhance vegetation growth in wet meadow regions during warm periods, and temperature was the limiting factor in Tibet during dry periods. The dominant role played by climate and human activities differed with location and targeted time period. Areas dominated by human activities are much smaller than those dominated by climate. The effects of grazing on grassland pasture were more obvious under unfavorable climate conditions than under suitable ones.
Highlights
As a dominant terrestrial ecosystem on the Qinghai-Tibet Plateau (QTP), grasslands play a pivotal role in linking the pedospheric, atmospheric, and hydrospheric systems in the region, and even the whole of Asia [1,2,3,4,5]
The adjusted−R2 is the the total amount for each component was calculated for each county, and the contributions of climatic contribution of climate to vegetation vigor and 1−R2 is the unexplained variation possibly caused and anthropogenic factors were calculated via Equation
Tibet pronounced shifts in the temporal climate trend occurred around the year 2000
Summary
As a dominant terrestrial ecosystem on the Qinghai-Tibet Plateau (QTP), grasslands play a pivotal role in linking the pedospheric, atmospheric, and hydrospheric systems in the region, and even the whole of Asia [1,2,3,4,5]. Due to its superior performance relative to prior versions and its capability for providing the longest time-series record from the early 80s, the GIMMS3g dataset has been widely used to identify vegetation activity trends and relationships with climatic factors [17,18]. We used the satellite-based vegetation index NDVI and the climatic dataset along with data on livestock grazing intensity to explore co-variations between vegetation dynamics and environmental variables across the QTP grasslands. The principal objectives of this research have been to: (1) Quantify the spatial and temporal variations of vegetation dynamics in response to climate change and anthropogenic activities on the plateau; (2) Identify the dominant factors regulating vegetation dynamics of the QTP grasslands prior to and post 2000
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