Treesearch

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...

Successful regeneration of eastern hemlock involves a complex biophysical process that commonly spans many years. Critical factors include a reliable source of seed, a suitable seedbed, a partially shaded environment, and several years of favorable moisture. Surface scarification appears critical as a means of site preparation. Even then, young hemlocks grow slowly, and commonly take several years to reach a size suitable for overstory release. Uniform partial cutting, shelterwood method, and patch cutting have all proven effective as strategies for regenerating hemlock. Reserve strip...

Eastern hemlock (Tsuga canadensis (L.) Carr.) is an important tree species in the mixed-species conifer forests of northern New England and adjacent Canada. Hemlock is very tolerant of understory conditions; consequently, it responds differently to various silvicultural treatments. In a long-term study at the Penobscot Experimental Forest in east-central Maine, shelterwood silviculture reduced the hemlock component in regenerating stands compared to parent stands, while hemlock increased in abundance and dominance under selection silviculture. On sites where hemlock is common, managers...

The stand dynamics and production of two one-acre plots of eastern hemlock (Tsuga canadensis L) in Connecticut have been followed for more than six decades. Data were recorded for all individual trees. One plot (Saltonstall) was established in 1924 after the removal of a hardwood overstory. This stand had a nearly pure, almost fully closed understory of hemlock that was subjected to partial cuttings in 1936, 1954, and 1956. The stand was lost to the hemlock woolly adelgid (Adelges tsugae) in 1993. The other plot (Perry) was established in 1931 in a nearly pure hemlock stand that had arisen...

Summarization of the limited growth information in mixed-species stands in New England indicates that eastern hemlock (Tsuga canadensis) may be one of the fastest growing species in diameter, second only to white pine. However, on some sites hemlock diameter growth is about equal to that of associated hardwoods. Hemlock grows slowly in height and often endures long periods of suppression, which limits the usefulness of site index curves. Suppressed trees, once released, may grow relatively faster than non-suppressed trees. Hemlock stands attain high basal areas per acre, up to 240 square...

In the early part of this century, considerable interest existed in the silviculture of hemlock (Tsuga canadensis (L.) Carr.) in the southern New England region, where it occurs in mixture with oak (Quercus spp.), white pine (Pinus strobus L.), birches (Betula spp.), and maples (Acer spp.). Difficulties encountered with the regeneration of white pine led to the idea that hemlock should be promoted through management as an alternative conifer sawtimber species. Research at forestry institutions in Connecticut and Massachusetts beginning in the 1920's demonstrated the ease with which...

Eastern hemlock has exacting germination requirements, and availability of suitable microsites for germination can limit the development of hemlock regeneration. A major contributor to those microsites is coarse woody debris. New methods for quantifying coarse woody debris have recently been developed that are complementary to strategies typically used in timber cruising. We discuss practical issues in estimating the abundance of coarse woody debris and associated germination microsites, and illustrate the techniques with reference to preliminary guidelines for coarse woody debris abundance.

This study reports patterns of regeneration and growth for 100 eastern hemlock (Tsuga canadensis (L.) Carr.) up to 20 inches (50 cm) dbh in two mixed-species selection stands on the Penobscot Experimental Forest in east-central Maine. The study stands are part of a U.S.D.A. Forest Service experiment in which eastern hemlock has remained stable over a 40-year period despite efforts to favor other species. Relative to red spruce (Picea rubens Sarg.) and balsam fir (Abies balsamea (L.) Mill.), eastern hemlock exhibits different growth patterns and canopy structures in response to frequent...

In October of 1852, Henry David Thoreau went for a stroll through a chestnut forest in Concord, Massachusetts and recorded the following impressions of a vibrant ecosystem.

Across its natural range in North America, eastern hemlock (Tsuga Canadensis (L.) Carriere) is an important resource for people and wildlife, but it is seriously threatened by the hemlock woolly adelgid (HWA) (Adelges tsugae Annand). From 10 to 20 percent of the hemlock resource is found in the Canadian provinces of New Brunswick, Nova Scotia, Ontario, Prince Edward Island, and Quebec. In the United States, hemlock is found across a wide range of forest types and stand conditions. There are 2.3 million acres of hemlock-dominated stands, but this species also is a common associate in many...