Abstract:

Using the Terra Moderate Resolution Imaging Spectroradiometer (MODIS) Normalized Difference Vegetation Index (NDVI) data (MOD13Q1) and land cover data, and the observed daily temperature, precipitation, and sunlight hours data obtained from 196 meteorological stations in the north and south of the Qinling-Huaihe region, this study explored the spatiotemporal characteristics of the vegetation dynamics in the region. It also analyzed the effects of the driving forces of climate change and human activities (such as urbanization and ecological restoration programs) on vegetation restoration and degradation between 2000 and 2019. As China's north-south transitional zone, the Qinling-Huaihe region has experienced overall greening (54.6% significant NDVI increase at P<0.05) and partial degradation (6.4% significant NDVI decrease at P< 0.05) from 2000 to 2019. The area of vegetation restoration was mainly in the Qinling-Daba Mountains, which are characterized by multi-dimensional zonal structures and biological diversity; and the percentage of NDVI increase was 96.7%. The other areas of restoration were the Qinba Mountains, Wushan Mountains and the Guanzhong Plain, which are all key implementation areas of ecological restoration programs. In terms of vegetation degradation, there was an NDVI decrease of 6.4%, which was mainly concentrated in the Yangtze River Delta urban agglomeration and sporadically spread across other rapid urbanization areas. With regard to the impacts of climatic factors on vegetation dynamics, the areas of NDVI change affected by temperature only accounted for 9.1% of the total area of the region, which is lower than the areas affected by precipitation (13.1%) and sunlight (14.5%). It indicates that the areas with significant (P<0.05) correlation between climatic factors and NDVI are limited. The reason is that there are the good hydrothermal conditions and irrigation facilities in the study region, climatic factors are not the primary limiting factors of vegetation growth. With regard to the driving forces of vegetation change, among the areas of significant greening (54.6%), 19.2% and 30.0% were identified to be related to climate change and ecological restoration programs, respectively. Ecological engineering had an influence on the vegetation dynamics of the Qinling-Huaihe region. The spatial pattern of significant restoration was consistent with the ecological restoration programs, such as the Qinling-Daba Mountains ecological protection and restoration and the Dabie Mountains ecological restoration programs. These findings enrich our understanding of the relationship between vegetation expansion, climate change, and human activities in the subtropical and warm-temperate zones of China.

Key words: climate change, vegetation dynamics, spatiotemporal analysis, ecological restoration, Qinling-Huaihe region