Asymmetric effects of diurnal warming on carbon allocation to leaves of marsh wetlands on the Tibetan Plateau

Using MODIS leaf area index and meteorological data from 2000 to 2020, this study analyzed the variations in carbon allocation to leaves (Cleaf) of marsh during the leaf green-up period and their response to climate change across the TP based on partial correlation and linear regression analysis methods. The regionally averaged Cleaf of marsh showed an increasing trend during the leaf green-up period from 2000 to 2020. Diurnal warming has asymmetric effects on Cleaf of marsh during different stages of the leaf green-up period. During the early leaf green-up period, warming preseason daytime temperature significantly reduced Cleaf in the southwestern region, while warming preseason daytime and night-time temperatures increased Cleaf in the central region. During the late leaf green-up period, preseason temperatures exerted significantly positive and negative effects on Cleaf in the southwestern and central regions, respectively. During the early leaf green-up period, preseason precipitation increases significantly enhanced Cleaf in the southwestern region, but decreased Cleaf in the central region. This study highlights the distinct impacts of climatic change on Cleaf during different stages of the leaf green-up period and indicates that the asymmetric effects of diurnal warming should be considered in simulations of marsh carbon allocation in the future.