Impact of nitrogen and importance of silicon on mechanical stem strength in Schoenoplectus acutus and Schoenoplectus californicus: applications for restoration

Nitrogen (N) and Silicon (Si) availability can affect the vigor and resiliency of plant communities. The effects of N on plant growth has been investigated in multiple species and is understood to promote growth. Though it is generally understood that Si aids in plant functions such as stem strength enhancement and herbivory defense, the role Si has not been explored in many wetland plant species. Tidal wetland plants are often subjected to high wind and wave energy, which can cause breakage or collapse of stems. This body of research investigated the combined effects of Si and N regimes to reduce the occurrence of stem collapse through its influence on stem strength. We investigated the effects of Si and N concentration on the growth, morphology, and physiology of Schoenoplectus acutus and Schoenoplectus californicus, two species of macrophytes that are commonly used in freshwater tidal restoration plantings. Individuals of each species were grown hydroponically in four different nutrient combinations (low Si and low N, low Si and high N, high Si and low N, and high Si and high N). Results indicated that increased N concentrations promoted aboveground biomass production, whereas increased Si concentration enhanced stem strength and decreased the likelihood of stem collapse and herbivory. Plants receiving a high Si and low N nutrient combination exhibited the most robust stems. Our findings emphasize the importance of Si, as well as N, in Schoenoplectus spp. growth and highlight the potential applications for these nutrients in enhancing tidal marsh management.