Ecophysiological responses of Phragmites australis and P. mauritianus to salinity and waterlogging

​AbstractRising sea levels and increased flooding due to climate change affect vegetation zonation and species composition. This study assessed the growth and physiological responses of two African haplotypes, Phragmites australis and P. mauritianus, to varying salinity and soil moisture conditions. Four-week-old plants were exposed to seawater concentrations of 0%, 5%, 10%, 20%, and 50% for five months under three soil moisture regimes: well-drained (WD), half flooded (½F) and fully flooded (F). Growth and physiological performance of both species were best under non-saline conditions and decreased with an increase in salinity. The 50% seawater treatment significantly reduced morphological and physiological parameters in both species across soil moisture regimes. There was a significant correlation between plant height and total number of leaves. Culm density increased with an increase in soil moisture in both species. Phragmites australis exhibited higher culm density than P. mauritianus. Biomass increased with soil moisture across all salinity levels, suggesting that salt stress was more severe under WD conditions. Phragmites australis allocated more resources to below-ground biomass, while P. mauritianus invested primarily in above-ground. Proline accumulation and electrolyte leakage increased with salinity in both species. Phragmites australis exhibited greater salt tolerance and invasive capacity than P. mauritianus. These results contribute to understanding the resilience of P. australis and P. mauritianus in response to salinity and waterlogging and provide insights for coastal ecosystem management.