Modeling the growth dynamics of Phragmites australis with flooding stress in the Middle Yangtze River

Phragmites australis is a common emergent plant in wetland ecosystems, and its growth process is closely related to various flooding conditions. A growth model was improved by incorporating the effects of water depth and inundation duration on P. australis growth. This model can simulate the growth processes of P. australis under different water depths and inundation durations, with validation results aligning well with measured data. Then the model was subsequently applied to simulate the growth process of P. australis on a typical floodplain of the Middle Yangtze River in 2019-2022. The results show that the aboveground biomass of P. australis decreased sharply due to the effect of flooding stress (with an inundation duration of 123 days and a maximum water depth of 5.64 m), resulting in a decline of 2176 g·m^-2 in biomass in 2020. The biomass reduction caused by flooding stress increased more rapidly with greater water depth and longer inundation duration. Therefore, the effect of flooding stress should not be ignored. In addition, good power function relationships were developed between the aboveground biomass reduction of P. australis and the number of inundation days or the days with water depth exceeding 2.0 m. The factor of flooding stress caused by water depth exceeding the inundation threshold played a dominant role in the growth dynamics of Phragmites australis.