Quantifying the impact of drought on net primary productivity of different vegetations in a typical large lake floodplain wetland, China

Wetland ecosystems are essential components of the global carbon and water cycles, but frequent and severe droughts pose significant disruptions to these ecosystems. As one of the most important Ramsar Wetlands globally, the Poyang Lake floodplain wetland ecosystem is facing severe drought challenges due to the combined impacts of climate change and human activities. This study investigated the spatio-temporal dynamics of net primary productivity (NPP) and its responses to drought in the Poyang Lake wetland from 1986 to 2020, using a process-based ecological model integrated with refined wetland vegetation classification datasets. The results indicated that the intra-annual NPP for most vegetation types exhibited two peaks, and the annual NPP ranged from 222.7 to 736.3 gC/m²/yr. Spatially, the high annual NPP values occurred in the southern and western regions of the wetland, while low values were found in the northern and eastern regions. Over the past 35 years, annual NPP decreased with the slope − 10.4 gC/m²/yr² across the entire wetland, with the most significant decline observed in the eastern region. Drought significantly altered NPP variability in the Poyang Lake wetland. Seasonal NPP slightly increased in spring and winter but decreased in summer and autumn during dry years. Specifically, the NPP declined by 57.2 % in the summer of dry years compared to that of normal years, causing annual NPP to decrease from 467.4 gC/m²/yr in normal years to 389.6 gC/m²/yr in dry years. Notably, the seasonal NPP of dominant communities, i.e., Phragmites australis-Triarrhena lutarioriparia, and Carex cinerascens, decreased by 77.8 and 114.5 gC/m²/yr in the summer of extreme drought and mild drought years, respectively, compared to normal years. The findings of this study contribute to understanding the response mechanisms of floodplain wetland vegetation to intensified droughts and accurately assessing regional carbon budgets.