Impacts of climate change on grassland carbon sink/source patterns in the Qinghai-Tibet Plateau

Grassland carbon sink/source is an important part of carbon budget and carbon balance in vegetation ecosystem. Distinguishing the response of carbon sink and carbon source to climate change can provide a scientific basis for reducing sources and increasing sinks. Based on MODIS NPP data and the soil respiration model, we quantified the spatial and temporal variability of Net Ecosystem Productivity (NEP) and carbon sink/source patterns in the Qinghai-Tibet Plateau (QTP) grassland ecosystem from 2001 to 2019, and analyzed the impact of climate change on grassland carbon sink/source using path analysis. The results show that the NEP in the grassland of the QTP presents a distribution pattern of higher in the east and lower in the west, with the average annual NEP of 54.41 g C m-2. Most of the grassland area in the QTP has functioned as a carbon sink since 2001. The areas of carbon sink are about 72.26×104 km2, with an average carbon sequestration of 79.61 Tg C a-1. The carbon source areas are about 47.82×104 km2, with an average carbon release of 14.26 Tg C a-1. Over the past 19 years, the trend of NEP in grassland of the QTP has been increasing. The trend of warming and humidification in the QTP was conducive to the increase of grassland NEP and the enhancement of carbon sinks. However, the effects of warming and drying trends on NEP varied greatly in different eco-geographical region systems.