Abstract
The arid region of northwest China provides a unique terrestrial ecosystem to identify the response of vegetation activities to natural and anthropogenic changes. To reveal the influences of climate and anthropogenic factors on vegetation, the Normalized Difference Vegetation Index (NDVI), climate data, and land use and land cover change (LUCC) maps were used for this study. We analyzed the spatiotemporal change of NDVI during 2000–2015. A partial correlation analysis suggested that the contribution of precipitation (PRE) and temperature (TEM) on 95.43% of observed greening trends was 47% and 20%, respectively. The response of NDVI in the eastern section of the Qilian Mountains (ESQM) and the western section of the Qilian Mountains (WSQM) to PRE and TEM showed opposite trends. The multiple linear regressions used to quantify the contribution of anthropogenic activity on the NDVI trend indicated that the ESQM and oasis areas were mainly affected by anthropogenic activities (26%). The observed browning trend in the ESQM was attributed to excessive consumption of natural resources. A buffer analysis and piecewise regression methods were further applied to explore the influence of urbanization on NDVI and its change rate. The study demonstrated that urbanization destroys the vegetation cover within the developed city areas and extends about 4 km beyond the perimeter of urban areas and the NDVI of buffer cities (counties) in the range of 0–4 km (0–3 km) increased significantly. In the range of 5–15 (4–10) km (except for Jiayuguan), climate factors were the major drivers of a slight downtrend in the NDVI. The relationship of land use change and NDVI trends showed that construction land, urban settlement, and farmland expanded sharply by 171.43%, 60%, and 10.41%, respectively. It indicated that the rapid process of urbanization and coordinated urban-rural development shrunk ecosystem services.
Highlights
Vegetation, as an essential portion of terrestrial ecosystems, plays a pivotal role in regulating the carbon cycle, climate change, and energy exchange through photosynthesis, evapotranspiration, and surface albedo [1,2,3,4]
The results showed that the cumulative precipitation and mean temperature in the growing season had a significant effect on vegetation dynamics
The overall trend of the growing season Normalized Difference Vegetation Index (NDVI) was upward in the Hexi Corridor and accounted for 95.43%
Summary
Vegetation, as an essential portion of terrestrial ecosystems, plays a pivotal role in regulating the carbon cycle, climate change, and energy exchange through photosynthesis, evapotranspiration, and surface albedo [1,2,3,4]. Changes in vegetation activity were mainly affected by biogeochemical effects and socio-economic factors on a global scale [5,6]. The biogeochemical effects mainly include the “fertilization effects” of CO2, regional climatic change, and nitrogen deposition [7,8]. Anthropogenic activities especially include land use change and socio-economic factors [9,10]. Changes in vegetation activities often serve as powerful indicators of the response to climate variability and anthropogenic activities [4,11]. Changes in vegetation greenness are affected by climate variability and anthropogenic factors [12,13]. Even anthropogenic disturbances on a small-scale and at low intensity can induce long-term changes in vegetation patterns and land use [14]
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