Differential growth and physiological responses to water level and soil type in two dominant macrophytes, Cladium jamaicense and Muhlenbergia capillaris , in South Florida, USA

Premise Wetland ecosystems experience strong spatial and temporal fluctuations in water levels, superimposed on a mosaic of soil/nutrient regimes, so wetland macrophytes either avoid or tolerate inundation in the context of their soil environment. How do wetland plants adjust their physiology and morphology in response to these water levels and soil types, and what traits are linked to inundation tolerance or avoidance? Methods In independent mesocosm experiments, we grew two co‐occurring plant species: Cladium jamaicense , more commonly found in long‐hydroperiod, peat environments, and Muhlenbergia capillaris , typically associated with short‐hydroperiod, marl environments. Plants were subjected for a year to one of three water levels in marl or peat soils. Plant traits such as morphology, biomass, nutrient content, and photosynthetic capacity were evaluated. Results Cladium jamaicense grew longer, wider leaves in response to higher water levels, whereas M. capillaris did not. Muhlenbergia capillaris photosynthetic rates were strongly reduced by high water level, while rates for C. jamaicense were less affected. Total biomass decreased with increasing inundation for both species, but shifts were only significant in M. capillaris . Conclusions Cladium jamaicense adjusted leaf morphology to both water level and soil type, whereas M. capillaris did not. Cladium jamaicense showed a growth response to avoid flooding, which was enhanced in peat soils, while M. capillaris showed a tolerance response, which was unaffected by soil type. These results can be used to predict these species’ responses to hydrologic and nutrient changes and distributions in other wetlands and to infer traits of other wetland species and their consequent distributions along hydrologic and soil gradients.