Common (Translated Scientific) Name: Eastern Hemlock - (Yellow Birch) Forest

Colloquial Name: Hemlock Mesic Forest

Hierarchy Level:  Association

Type Concept: This mesic hemlock evergreen forest is found in the Great Lakes region of the United States and Canada. Stands occur on deep, acidic soils that may be poorly drained. The overstory of this community is strongly dominated by Tsuga canadensis, typically around 25 m tall. Betula alleghaniensis is often present in the canopy and subcanopy, but at less than 25% cover. Other species that are a minor component of the canopy include Abies balsamea, Acer rubrum, Acer saccharum, Pinus strobus, Tilia americana, and Thuja occidentalis. The sapling layer may also contain Abies balsamea and Thuja occidentalis, especially in canopy gaps. Shrubs are rare and herbaceous species only moderately abundant under the dense evergreen canopy; however, where gaps occur, Acer pensylvanicum, Acer spicatum, Amelanchier spp., Gaultheria procumbens, Lonicera canadensis, and Rubus idaeus may be moderately abundant. The herbaceous layer is poor under drier, more evergreen stands, and richer under more moist and somewhat deciduous stands. Herbaceous species found in this community include Aralia nudicaulis, Clintonia borealis, Coptis trifolia, Cornus canadensis, Dryopteris carthusiana, Huperzia lucidula, Maianthemum canadense, Oxalis montana, Pteridium aquilinum, Streptopus lanceolatus var. longipes, and Trientalis borealis. A sparse to dense moss layer includes Brachythecium reflexum, Callicladium haldanianum, Dicranum flagellare, Dicranum montanum, Mnium marginatum, Plagiothecium laetum, Polytrichum commune, Ptilidium pulcherrimum, and Tetraphis pellucida.

Diagnostic Characteristics: No Data Available

Rationale for Nominal Species or Physiognomic Features: No Data Available

Classification Comments: This type varies from almost pure Tsuga canadensis to more of a mix with Betula alleghaniensis, but the deciduous component is generally less than 25% cover (see e.g., Chambers et al. 1997, Ecosites 30.1 and 30.2). If hardwoods exceed 25%, the type is placed in ~Tsuga canadensis - Acer saccharum - Betula alleghaniensis Forest (CEGL005044)$$, but logged stands, or remnants that occur in a matrix of secondary growth hardwoods, can be difficult to assign. Chambers et al. (1997) recognize a moist and a dry type in central Ontario. Those are treated as variants of the one type here. In Michigan this type is on the clay lakeplain in the western Upper Peninsula and in the Saginaw Bay Lakeplain. The data by Rogers (1980), who examined pure hemlock stands (many of them less than 2 ha in size) from Wisconsin to Nova Scotia, make clear that there are few species strictly associated with a pure hemlock versus a mixed hemlock-hardwood type, and also indicate that some distinction between a Great Lakes versus northeastern United States/eastern Canada has some merit, as done for the mixed hemlock-hardwood type (CEGL005044 versus ~Tsuga canadensis - (Betula alleghaniensis) - Picea rubens / Cornus canadensis Forest (CEGL006129)$$). No pure evergreen hemlock type is currently recognized in the northeast because of its small patch size.

Similar NVC Types: No Data Available

note: No Data Available