The effects of plant density on biomechanical properties of a tidal wetland macrophyte; Zizania aquatica

Tidal freshwater wetlands provide a variety of ecological and social benefits such as habitat and protection of shorelines from storm surges. Unfortunately, sea level rise and development pressures have greatly impacted these ecosystems. Widespread historical wetland losses and ongoing vulnerability underscore the importance of understanding tidal wetland responses and resilience to stressors in order to achieve successful management of these resources. Recently reported accelerated rates of sea level rise are of particular concern. The role of wetland macrophytes in responding to sea level rise by changing stem density and morphology to create feedbacks with sediment capture has been well documented in tidal salt marshes. In some cases, the plasticity of these morphological responses results in changed structural characteristics of the plants. However, these processes have been less well studied in freshwater tidal systems. We will present the results of a study focused on biomechanical and structural properties of Zizania aquatica, a dominant species in tidal freshwater marshes of the Chesapeake Bay. The project’s principal objective is to determine if plant density has an effect on stem “factor of safety”; a biomechanical property that indicates how well Z. aquatica stems can withstand water velocities before structural failure. Measurements in experimentally thinned plots will be presented and include plant height, tissue density, breaking and bending stress, crown weight and stem diameter to calculate the factor of safety of high and low density plots. Implications for the response of this species to increased inundation associated with sea level rise will be discussed.