Determining the contributions of climate change and human activities to vegetation dynamics in agro-pastural transitional zone of northern China from 2000 to 2015

The vegetation in the agro-pastoral transitional zone of northern China (APTZNC) was significantly restored, and both climate change and ecological restoration projects contributed to vegetation activities with varied proportion. Since few decades ago, APTZNC has undergone significant land degradation and climate change, threatening regional sustainable development, and in response to such ecological crises, multiple ecological restoration projects were implemented, which have caused a profound impact on the terrestrial ecosystem. Taking agro-pastural transitional zone of northern China (APTZNC) as the study area, this study used 16-year (2000-2015) net primary productivity (NPP) as an important indicator of the arid and semi-arid ecosystem's productivity, combing meteorological data in same period to (1) monitor the vegetation dynamics affected by both climate and ecological restoration projects; (2) detect climate changing trend, including annual precipitation, air temperature, and sunlight hours; (3) explicitly distinguish driving forces of climate change and ecological restoration projects on vegetation dynamics based on correlation analysis. The results demonstrated that (1) the annual NPP indicated overall greening (48.77% significant restoration) and partial degradation (0.39% significant degradation) in APTZNC; (2) the annual precipitation was the main factor that widely influences vegetation growth, and the area with significant influence accounted for 55.53%; however, the area with significant temperature influence only accounted for 1%, and the area affected significantly by sunshine hours accounted for 14.33%; (3) In the area of significant greening with proportion of 48.77%, of 26.93% was related to climate change, of 19.80% was related to ecological conservation programs, and of 2.05% was related to multiple factors. In the significantly degraded area with proportion of 0.39%, of 0.1% is related to climate change and of 0.29% is abnormally degraded. Our study is expected to accelerate the understanding of vegetation dynamics and its driving mechanisms, and provide support for scientifically formulating and adjusting ecological restoration projects in APTZNC.