Asymmetric Impacts of Diurnal Warming on Vegetation Carbon Sequestration of Marshes in the Qinghai Tibet Plateau

As the world's Third Pole, the Qinghai-Tibet Plateau has a large area of marshes, which plays an important role in global carbon cycle. The net primary productivity (NPP) of vegetation is a crucial index for measuring the carbon flux of marsh ecosystems. Understanding the change in marsh NPP and its response to climatic change is important for assessing carbon sequestration of marsh ecosystems. Based on MODIS NPP data and climate data from 2000 to 2020, this study analyzed the spatiotemporal change in marsh NPP and determined its relationship with climate factors on the Qinghai-Tibet Plateau. The results showed that the average annual NPP of marshes on the Qinghai-Tibet Plateau increased significantly by 11.70 +/- 1.07 g C center dot m(-2)/10a during 2000-2020, with an average value of about 184.37 +/- 11.12 g C center dot m(-2). Spatially, the annual marsh NPP showed obviously increasing trend in the northeast but decreasing trend in the southwest regions. Daytime maximum and nighttime minimum temperatures had asymmetric effects on marsh NPP, with a larger positive effect of minimum temperature. Warmed minimum temperatures in winter and spring significantly increased the annual marsh NPP on the Qinghai-Tibet Plateau. The increasing maximum and minimum temperatures in the summer obviously promoted the vegetation growth in marshes. Additionally, the increasing spring precipitation could significantly increase the marsh NPP. Our results highlight that the asymmetric impacts of daytime and nighttime temperatures on marsh vegetation should be adequately considered in predicting marsh carbon sequestration on the Qinghai-Tibet Plateau, especially in the context of global asymmetric diurnal warming.