Response of vegetation variation to ecological restoration project and climate change in the Taihang Mountains, China

Vegetation response to the combined effects of human and nature has raised extensive controversy. The relative contributions of ecological restoration and multiple climate factors on vegetation variation remain unclear. Combining spatial and temporal changes in fractional vegetation cover (FVC) and net primary productivity (NPP) from 2000 to 2021, we assessed the trend of these two indicators and quantified the impact of ecological restoration and climate factors on vegetation variation using partial correlation and residual analysis. The results indicated that: (1) From 2000 to 2021, vegetation restoration in the Taihang Mountain area was notably successful. FVC increased by 5.71% over 22 years with a change trend of 0.0018 per annum. The cumulative growth rate of NPP over the same period was 42.03%, corresponding to an average annual increase of 5.492 g(C)·m^-2·a^-1. (2) During the 22-year period, the contribution rates of ecological engineering to FVC and NPP were 65.13% and 64.33%, respectively. Ecological restoration was the dominant factor affecting vegetation change, and its impact was increasing in over 90% of the regional projects. The primary climate controlling factor of NPP was precipitation, while FVC responded synergistically to precipitation (primary) and temperature (secondary). Overall, the impact of precipitation on vegetation was 1.5 times that of temperature. (3) Among various ecological restoration types, grassland restoration contributed the most to vegetation change, followed by forest land restoration. This study offers valuable scientific insights that can guide the sustainability of vegetation ecology in semi-arid mountainous areas.