Landscape Patterns of Forb Pannes Across a Northern New England Salt Marsh

Abstract

Most salt marshes are dominated by graminoids, but patches dominated by a diverse assemblage of perennial forbs, known as forb pannes, occur on marshes in north temperate areas. These pannes and their associated species diversity appear to be highly responsive to anthropogenic change, including climate warming. We mapped all of the forb pannes on a salt marsh in Wells, Maine in order to 1) determine if geospatial features were related to panne location and species composition, and 2) record a baseline to compare with future responses to anthropogenic change. Forb pannes occupied approximately 5% of the high marsh surface, with sizes ranging from 7 m 2 to 5000 m 2 . Pannes themselves were clustered at river/creek edges and near pools. Within pannes, species diversity was highest away from pools and the river mouth, and relative abundance of Plantago maritima was related to spatial variables. These results suggest that forb panne distribution and community structure are influenced by spatial variables and reinforce the notion that forb pannes may be used to track salt marsh responses to global change.

Classification and environmental correlates of tidal wetland vegetation in Nova Scotia, Canada

“…Although many studies from the east coast of the US report the presence of a distinct vegetation type occurring in pannes created by disturbance to high marsh vegetation (Ewanchuk and Bertness 2004, Griffin et al 2011, no comparable communities were identified in any of the sites in this study. In general, forb pannes are largely absent from marshes in all three regions of the province, despite the occurrence of large amounts of sea ice causing disturbances in the Bay of Fundy region.…”