Detection and attribution of vegetation dynamics in the National Barrier Zone of China by considering climate temporal effects

Reliable detection and attribution of vegetation dynamics in the National Barrier Zone (NBZ) of China is fundamental to determining the effectiveness of ecological restoration projects and developing adaptive conservation strategies. Nevertheless, limited knowledge of the climate temporal effects on vegetation growth creates uncertainties in understanding vegetation-climate interactions. We evaluated the spatial and temporal patterns of climate temporal effects on vegetation in the NBZ by the Normalized Difference Vegetation Index (NDVI) and climate datasets during 1982-2015. The residual trend analysis was then utilized to attribute vegetation dynamics before and after the implementation of the "Grain for Green Program" (GGP) launched in 1999. The results indicated that the NBZ experienced significant and persistent greening during 1982-2015, with most areas recording a greater increase in NDVI after the GGP than before it was implemented. Climate temporal effects affected over 75 % of the vegetated areas in the NBZ, and the overall explanations of NDVI variations explained by climate variables increased by 5.7 % when time-lag and cumulative effects were considered. Precipitation was the dominant climatic controller of vegetation dynamics in the northern sand belt, whereas temperature was the principal controller in other zones. Additional cropland before the implementation of the GGP in the NBZ was 28,807 km2, which was ten times more than what was added after the GGP was implemented. Climate change and human activities explained 47.4 % and 52.6 % of vegetation variations in the NBZ, respectively, with all zones except the ecological barrier of Qinghai-Tibet Plateau (TPEB) being dominated by anthropogenic factors. Anthropogenic contributions to vegetation dynamics increased significantly after the implementation of the GGP. The study offers theoretical guidance for developing ecological conservation strategies in China.