Spatiotemporal Variations in the Rate of Canopy Development and Senescence of Marsh Wetland Vegetation and Their Responses to Climate Change in China

Understanding the changes in the rate of vegetation development and senescence of marsh wetlands and their responses to climate change is important for revealing the regional characteristics of biogeochemical and biophysical cycles. Using Moderate Resolution Imaging Spectroradiometer Normalized Difference Vegetation Index and meteorological data from 2000 to 2020, we analyzed the spatiotemporal variations in the rate of vegetation development and senescence in the marshes of China and their responses to climatic change. We found that the national average rate of vegetation development increased significantly (P < 0.05) in May and decreased in July. The rate of vegetation senescence slowed in September and accelerated in October. Increased preseason precipitation and temperature accelerated the rate of canopy development of marsh vegetation in May, but slowed down the rate of senescence in September. Regionally, in the Tibetan Plateau, Northeast China, and Inner Mongolia, warmer preseason nighttime temperatures had larger accelerating effects on promoting vegetation development than did daytime temperatures in May. Increasing preseason nighttime temperatures promoted marsh vegetation growth in August in the Tibetan Plateau, while increasing preseason precipitation slowed vegetation senescence in September in the Tibetan Plateau and Northeast China. In Northeast China and Inner Mongolia, increasing preseason temperatures slowed senescence in September. The results indicate that precipitation and temperature have different influences on the rate of marsh vegetation development and senescence in different regions of China and imply that the asymmetric impacts of diurnal temperatures must be considered when modeling future marsh vegetation development and senescence rates.