Responses of Narrowleaf Cattail (Typha angustifolia) to Combinations of Salinity and Nutrient Additions: Implications for Coastal Marsh Restoration

Narrowleaf cattail (Typha angustifolia) is an exotic, invasive species in North America that has become abundant in many tidally-restricted salt marshes. Restoration of tidal flow to these wetlands results in elevated salinities that should favor the establishment of native salt marsh halophytes while reducing the abundance of narrowleaf cattail. However, there is some uncertainty about the salinity tolerance of narrowleaf cattail, which makes it difficult to predict vegetation trends and to interpret the actual results of restoration. Moreover, the effect of soil nutrient status on salinity tolerance of this species is virtually unknown, although many restoration projects occur in heavily urbanized settings with substantial allochthonous nutrient inputs. In this study, a salinity and nutrient addition experiment was conducted in a greenhouse to determine the effect of mineral nutrition on salinity responses in narrowleaf cattail. Within high salinity (~ 32 ppt) treatments, nutrients enhanced final biomass. Within the intermediate salinity (~ 17 ppt) treatments, nutrients significantly increased the number of leaves per shoot, sum of all leaf lengths, and final biomass. Under low salinity (~ 6 ppt) conditions, nutrient addition increased the mean height of the tallest shoot, mean height of all leaves, sum of all leaf lengths, and final biomass. The salinity responses and observed reductions in salinity-induced physiological stress by nutrient addition provide some context for forecasting and analyzing vegetation change in response to tidal restoration.