Tsuga canadensis in Ohio: Synecological and phytogeographical relationships

Abstract

Tsuga canadensis is the dominant in four topo-edaphic associations and one edaphic association in Ohio. WhileTsuga may occur withPinus strobus and a variety of deciduous trees (e.g.,Fagus grandifolia, Acer saccharum) in these communities, only hemlock is persistently reproducing. As compared with the contiguous mesophytic deciduous forest, these associations have a depauperate understory, a possible consequence of the shallow and generally coarse soils and low light intensity in these habitat types. The narrow gorge microhabitat of theT. canadensis-Dryopteris intermedia habitat type and the northerly exposure of theT. canadensis-D. marginales habitat type with lower light intensity and lower evapotranspiration allow the establishment and maintenance of hemlock to the exclusion of most deciduous tree species. In addition, the gorges provide some fire protection, and due to their general inaccessibility, protection from logging. These Ohio hemlock associations bear little floristic similarity to the more extensive climatic climax hemlock communities in southern Ontario, possibly reflecting elimination of most boreal associates in Ohio with climatic change since the end of the Pleistocene.