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• A statistical model of flood elasticity under changing conditions was derived. • The model was applied in a typical tropical monsoon basin of Thailand. • The flood peaks are expected to increase due to deforestation and climate change. • The absolute value of storm-flood elasticity is larger for shorter return periods. • Climate change tends to dominate future flood changes over deforestation. Storms and the resultant floods have caused considerable fatalities and have raised increasing global concerns in the context of climate change and socioeconomic development. The relationships between storms and floods have been explored as storm-flood elasticity, but the shifts of the storm and flood peak distributions under changing conditions have not been sufficiently considered. In this study, a novel statistical model that reflects the relationship between storm distribution and flood distribution under changing conditions has been developed. Due to its concise structure, the statistical model can be easily used to explicitly derive the storm-flood elasticity and quantify the future flood responses to changing climatic and land surface conditions. The statistical model is then applied in a typical tropical monsoon basin in Southeast Asia, the Upper Chao Phraya River Basin (UCPRB), which underwent significant climate change and deforestation. The shifts of the storm and flood frequency curves are modeled via GAMLSS with the aid of wet season dew point and forest cover ratio, and the curves derived from statistical models prove to be consistent with the results from the more computationally intensive process-based model. By examining flood elasticity including storm-flood elasticity and forest-flood elasticity under changing conditions, the response of flood peak to storm peak and forest cover change is expected to weaken as the return period increases. Future flood peaks are expected to change substantially under most emission scenarios, and the changes can be mostly attributed to climate change rather than deforestation. The dominance of climate change over deforestation strengthens in the long-term future and is more evident for shorter return periods, highlighting the indispensable role of climate change mitigation in reducing future flood risks in the UCPRB. The analytical framework developed by this study can also be applied in other climate regions besides tropical regions, which could help to provide insights for future changes in floods and their relationship with climatic and land surface characteristics under changing conditions. [ABSTRACT FROM AUTHOR]

[Display omitted] • CO 2 fluxes were measured in three subtropical mangroves for 16 site years. • VPD stress inhibits mangrove productivity during both exposed and inundated periods. • Meteorological factors and VPD have interactive effects on mangrove productivity. • Tides have independent effects on mangrove productivity through salinity changes. • The threshold effect range of VPD stress on mangrove productivity is 2.50–2.95 kPa. Subtropical mangroves have great potential to sequester atmospheric carbon dioxide (CO 2) and thus significantly contribute to climate change mitigation. Meanwhile, the carbon cycling processes in subtropical mangroves are vulnerable to the changing climatic conditions, such as the warming-induced vapor pressure deficit (VPD) increases. However, the impacts of VPD on net ecosystem production (NEP) in subtropical mangroves remain poorly understood due to a lack of detailed assessment of NEP responses to VPD among different mangrove forests over a long-term observational period. In this study, we deployed eddy-covariance systems to measure net ecosystem CO 2 exchange at three subtropical mangrove forests for 16 site-years, comprising two natural and one artificial forests. We employed a state-of-the-art data-driven modeling approach (i.e., Shapley additive explanations (SHAP) framework based on extreme gradient boosting model), which enabled us to explore the interactive effects of meteorological and tidal factors (e.g. salinity) with VPD on the mangrove NEP. We revealed that air temperature, global solar radiation (GR) and wind speed have significant interactions on the response of NEP to VPD stress in subtropical mangroves. For instance, when GR was high, the SHAP interaction values of VPD and GR on NEP decreased with increasing VPD, but when GR was low, the trends were the opposite. However, instead of identifying interactive effects between tidal salinity and VPD on mangrove NEP, we came across potential independent influence of salinity on the same. SHAP analysis was also able to disentangle the impact of VPD from other abiotic drivers. Thus, we evaluated the threshold effect of VPD stress on NEP loss in subtropical mangroves and observed a range of 2.50–2.95 kPa. Above this range, VPD stress leveled off. The subtropical mangrove responses to VPD should be therefore considered in the dynamic global vegetation models to increase the accuracy in carbon cycle simulations in the future. [ABSTRACT FROM AUTHOR]