Vegetation composition and structure in two hemlock stands threatened by the hemlock woolly adelgid

Abstract

We quantified the vegetation composition and structure of two hemlock (Tsuga canadensis) ravines in the Delaware Water Gap National Recreation Area threatened by the hemlock woolly adelgid (Adelges tsugae). Hemlock accounted for more than 50% of the canopy basal area (ravine mean = 52.3 m² ha^-1) and more than 75% of the understory trees and saplings (ravine mean = 599 stems ha^-1). Other common trees were black birch (Betula lenta) and red maple (Acer rubrum); white pine (Pinus strobus) was abundant at one site. The forest understories were shady with limited cover of vascular plants (ravine mean = 5%). Average understory light levels ranged from 6% of the above-canopy light in the more open stand to only 3% in the more closed-canopy stand. Two ferns, Dryopteris intermedia and Dennstaedtia punctilobula, were the most abundant herbaceous plants with a patchy distribution. Bryophyte cover averaged 9%; Mnium hornum and Hypnum imponens were the most abundant mosses.

Parent Publication

• Proceedings: symposium on sustainable management of hemlock ecosystems in eastern North America

Citation

Battles, John J.; Cleavitt, Natalie; Fahey, Timothy J.; Evans, Richard A. 2000. Vegetation composition and structure in two hemlock stands threatened by the hemlock woolly adelgid. In: McManus, Katherine A.; Shields, Kathleen S.; Souto, Dennis R., eds. Proceedings: Symposium on sustainable management of hemlock ecosystems in eastern North America. Gen. Tech. Rep. NE-267. Newtown Square, PA: U.S. Department of Agriculture, Forest Service, Northeastern Forest Experiment Station. 55-61.