Vegetation quality and its change in the Three North Shelterbelt Forest region in China

The Three North Shelterbelt Forest (TNSF) region in northern China is the largest artificial afforestation area in the world. Vegetation quality in the TNSF region has been improved greatly in recent years. This article presents a new approach to characterize vegetation quality by coupling vegetation productivity and coverage, examining the trend of vegetation quality from 2000 to 2021 at 1 km x 1 km spatial resolution by the linear regression trend method, and analyzing the driving forces of that trend. The results revealed a significant spatial difference of vegetation quality. Higher vegetation quality was found in the east and southeast of the TNSF region. Improvement of vegetation quality was found in approximately 80% area of the TNSF region, at a rate of 0 similar to 52 g C m(-2)yr(-1) with alpha = 0.05 significance between 2000 and 2021. Vegetation quality deteriorated in a few areas. The increase in CO2 concentrations and annual precipitation facilitated the improvement of vegetation quality, but also human efforts in ecological protection and restoration accelerated the improvement of vegetation quality under the current climate change background. The results might contribute to designing future ecological projects and the scientific adjustment of vegetation restoration strategies.