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• We selected Tibetan Plateau to examine net primary production during 2000–2018. • The NPP in permafrost region had a steadier and faster increasing rate. • Soil water and temperature were the main reasons for NPP changes. • The NPP values will show greater interannual changes in the future. Permafrost affects soil water and soil temperature regimes; however, its effects on net primary production (NPP) remain unknown. Here, we examined temporal-spatial changes in grassland NPP during 2000–2018 in permafrost and permafrost-free areas on the Qinghai–Tibetan Plateau using the random forest (RF) and radial basis function artificial neural network (RBF-ANN). Our results indicated that the areas that showed increasing, decreasing, and non-significant trends for NPP accounted for 13.88%, 1.90%, and 84.22% of the permafrost area, respectively. For the permafrost-free areas, these NPP trends accounted for 22.25%, 2.68%, and 75.07% of the permafrost-free area, respectively. The mean NPP in the permafrost regions showed a faster and steadier (1.520 g C/m2/yr, p < 0.05) increase than in non-permafrost regions (1.224 g C/m2/yr, p < 0.05). The Biome-BGC model confirmed that these spatial NPP patterns could be attributed to differences in soil water and soil temperature between permafrost and permafrost-free areas. Both the soil temperature and soil water content in permafrost sites exhibited relatively lower variance than in permafrost-free sites. Although many factors may be attributed to these patterns, our results suggest that there is a possibility that the relatively stable change in permafrost NPP can be explained by the fact that permafrost can regulate soil water and temperature regimes. Therefore, climate warming can increase NPP in cold regions, and permafrost degradation may destabilize the grassland ecosystem, which may cause NPP values to exhibit greater interannual changes in the future. [ABSTRACT FROM AUTHOR]

Global warming can affect vegetation growth, while the tempo-spatial responses of vegetation to climate change remain largely unclear. In this study, we selected China as the study area, and we equally divided the time span into two periods (2001–2009 and 2010–2017). We examined the vegetation indicators, including NIR V , SIF, and GPP, using correlation analysis, multiple linear regression analysis, and contribution calculation. The results showed that climate warming overall promoted vegetation growth during the two periods, and vegetation growth showed no acclimation response to climate warming. The effects of climate warming on vegetation growth showed great spatial heterogeneities, with a promoting effect in the southern part of the eastern monsoon region and the southeastern part of the Qinghai-Tibet region, while this effect was not obvious in the arid and semiarid regions of northwest China and the western part of the Qinghai-Tibet region. We argue that the promoting or suppressing effects of climate warming on vegetation are mainly regulated by water availability. Our findings showed the relative persistent effects of climate warming on vegetation growth, and the effects are largely determined by water availability. The results highlight the importance of water availability in vegetation growth under future climate warming scenarios. • Effects of warming on vegetation growth have great spatial heterogeneities in China. • Climate warming largely promted vegetation growth in China during 2001-2007. • The promoting and inhibiting effects of global warming on vegetation were regulated by water availability. [ABSTRACT FROM AUTHOR]