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

Heike Markus-Michalczyk^1,2,*, Michelle L. Crawford¹, and Andrew H. Baldwin²

¹University of Maryland, Department of Environmental Science and Technology, 1426 Animal Science/Agricultural Engineering Building, College Park, MD 20742. ²NIOZ Royal Netherlands Institute for Sea Research, Department of Estuarine and Delta Systems, and Utrecht University, PO Box 140, 4400 AC, Yerseke, The Netherlands. *Corresponding author.

Northeastern Naturalist, Volume 27, Issue 2 (2020): 229–241

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.

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