Comparison of water depth tolerance in two major wetland macrophytes, Phragmites australis and Typha angustifolia

Two major emergent macrophytes, Phragmites australis and Typha angustifolia, show a clear zonation with respect to water depth, i.e., P. australis occupies shallower water than T. angustifolia. However, the reasons for this interspecific difference is unclear. Therefore, this study focused on the features that enable T. angustifolia to survive at greater water depths than P. australis. In both outdoor and greenhouse experiments, P. australis did not survive at the deepest water depth and showed significantly lower biomass, nitrogen content, and photosynthesis in most deep and/or aerated water than T. angustifolia. Differences in tolerances to changes in the water depth and responses to root aeration may underlie the clear zonation of the two species. As T. angustifolia and P. australis are both very common in wetlands around the world, understanding the causal factors determining their depth distributions, such as differences in photosynthetic rate at different depths, will be of great importance for managing or controlling these species.