Untangling the effects of management measures, climate and land use cover change on grassland dynamics in the Qinghai-Tibet Plateau, China

Multiple large-scale ecological conservation programmes have been launched by the Chinese Government to combat grassland degradation across the Qinghai-Tibet Plateau (QTP) since 1999. However, the mechanisms by which these ecological initiatives might affect grassland changes remains unknown. Here, we examined the land use cover change (LUCC) and net primary productivity (NPP) of the grassland in the QTP in 2001-2016. The effects of LUCC, management measures, and climate variation on grassland NPP were quantitatively evaluated. The grassland area had a net increase of 96,397 km(2), which could be attributed to the conversion of desert and forests. The total NPP of grassland increased by 154,073.7 GgC center dot yr(-1) in 2001-2016, of which the contribution of climate and human factors occupied 35.58% and 64.42%, respectively. Specifically, climate variation caused an overall increase of 54,823.24 GgC center dot yr(-1)in grassland total NPP. The climate-dominated NPP decrease was widely found in the eastern and southern QTP. The contribution of LUCC and management measures to the increase of grassland NPP was 62.78% and 37.22%, respectively. This increase was mostly found in the mid-east region of the QTP, which could sufficiently counteract the negative effect of climate variation on NPP. Overall, these findings seem to demonstrate that these ecological restoration programs have substantially promote the increase of grassland NPP and contribute to understanding the degree to which the grassland ecosystem may respond to the LUCC and management measures under the ecological restoration projects, which are essential to developing more effective ecological measures for future grassland restoration in the QTP.