Salinity Tolerance and Occurrence of Salix nigra Marshall (Black Willow) in Tidal Wetlands of Chesapeake Bay Tributaries

Abstract

Salix nigra Marshall (Black Willow) is a pioneer tree species that establishes in North American river floodplains and is widely used for bank stabilization. However, its salinity tolerance and occurrence in tidal wetlands of estuarine systems along the North American Atlantic coast is largely unknown. Climate change accompanied by land subsidence and changes in precipitation pattern induce increases in salinity that may affect coastal vegetation. Alteration of hydromorphology of coastal plain estuaries causes additional increases in salinity that affects forested tidal freshwater wetlands. We investigated the salinity tolerance and occurrence of Black Willow in tidal wetlands of 2 Chesapeake Bay tributaries and in a greenhouse hydroponic experiment. A salinity of more than 1 part per thousand (ppt) salt limited the willows' occurrence in the field and the cuttings' performance in the experiment. Dry mass was significantly lower in salinity of 2 and 3 ppt compared to the control and salinity of 1 ppt. Cuttings originating from tidal freshwater wetlands developed more belowground biomass and leaves than cuttings from brackish wetlands. The better performance of cuttings originating from tidal freshwater wetlands may indicate a higher resilience to short-term increases in salinity in tidal freshwater wetland forests with implications for tidal forest restoration in eastern North America.