Abstract
The Normalized Difference Vegetation Index (NDVI) is sensitive to changes in surface vegetation cover. Research into how climate change impacts surface vegetation cover is essential to manage ecological systems and promote green development. The Western Henan Mountains, located in the transitional zone between the northern subtropical and warm temperate zones of China, is an ideal location to study the impacts of climate change on surface vegetation cover. Combining a digital elevation model (DEM) with temperature and precipitation data; and MODIS-NDVI imagery (2000∼2017) for the Western Henan Mountains, this study explores variations in the growing season NDVI and its response to climate change. Results show that there are significant changes with fluctuations in NDVI values from 2000 to 2017. NDVI increased at a growth rate of 0.027 per decade (p < 0.05) overall, indicating vegetation conditions have gradually improved. Although the NDVI value showed an overall increasing trend, 19.12% of the areas showed a decreasing trend, interspersing and intersecting spatially, showing significant spatial differences. NDVI increased initially, but then decreased as a function of elevation, which was shown to be proportional to slope and independent of aspect. Variables including elevation and slope gradient are shown to provide high explanation of NDVI variability, whilst temperature is shown to have a more significant impact on NDVI than precipitation. However, vegetation responses to temperature and precipitation covaried with both slope and aspect. Positive NDVI trends were strongest at low elevations (i.e., <1,100 masl), which we attribute to vegetation restoration activities. Lower NDVI values characterized gentle slopes (<5°), whilst higher values were, in contrast, associated with steeper slopes (5∼10°). This study highlights the complex mechanisms and their relations governing vegetation response to climate change and should form an instructive basis for both future modeling studies investigating the response of vegetation to future global warming.
Highlights
Vegetation comprises a critical component of ecosystems connecting the atmospheric, hydrological and pedological systems (Yang et al, 2010; Piao et al, 2011)
The Western Henan Mountains are in the transition zone between the northern subtropical and warm temperate zones of China
We demonstrate the response of vegetation dynamics to both temperature and precipitation in the study area
Summary
Vegetation comprises a critical component of ecosystems connecting the atmospheric, hydrological and pedological systems (Yang et al, 2010; Piao et al, 2011). The sensitivity of vegetation cover to climate change has become a major research focus considering the unprecedented rates and impacts of anthropogenic global warming on the biosphere. Understanding the driving mechanisms controlling mountain vegetation is essential to project future spatial patterns of vegetation change in response to global warming in these regions, and as such constitutes a pressing issue for climate change research. Some progress has been made in the study of mountain vegetation changes in China, the Sanjiangyuan area of Tibet Plateau, Hengduan Mountains, Tianshan Mountains, Changbai Mountains, Qilian Mountains and Qinling Mountains (Kessler, 2000; Long, 2003; Zhang et al, 2004; Yao et al, 2010). The region represents a topographical transition zone between the second and third steps, displaying diverse topographic characteristics (Zhang et al, 2019)
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