This habitat description is reprinted by permission from the report:  Kiilsgaard, C. 1999. "Land Cover Type Descriptions, Oregon Gap Analysis (1998 Land Cover for Oregon)." Oregon Natural Heritage Program, Portland, OR.

MOUNTAIN HEMLOCK SUBALPINE FOREST (33)

Geographic Distribution. Mountain hemlock (Tsuga mertensiana) ranges throughout the Cascades at higher elevations (generally above 4500 ft). In the southern Cascades and Siskiyou Mountain ranges the mountain hemlock cover type grades into the Shasta red fir (Abies magnifica var. shastensis)/mountain hemlock forest cover type. Mountain hemlock is also found in the Wallowa Mountains of northeastern Oregon. In both the Siskiyous and Wallowas, mountains hemlock is not as common, nor as extensive, as in the Cascades.

Structure and Appearance. At the lower elevation range of mountain hemlock this cover type is a forest that can have a multi-storied canopy, although it typically tends to single story. In these conifer dominant forests tree size is considerably smaller and regeneration more difficult than in lower elevation conifer cover types due to persistent snowpack and short growing season. Mountain hemlock, at its upper elevation range, grades into alpine parkland. Parkland settings are considered as a mosaic of treeless openings with clumps of closed canopy trees.

Composition. Mountain hemlock typically dominates the overstory in this upper elevation conifer forest. Pacific silver fir (Abies amabilis), lodgepole pine (Pinus contorta), western white pine (Pinus monticola), western hemlock (Tsuga heterophylla), and Douglas fir (Pseudotsuga menziesii) may be present in the overstory. In parkland mosaics mountain hemlock may appear in pure clumps, or mixed with subalpine fir (Abies lasiocarpa) or whitebark pine (Pinus albicaulis).

Shrubs and forb layer are typically sparse and species poor. Several of the Vaccinium genus are the most commonly found shrubs, big huckleberry, (V. membranaceum), grouse whortleberry (V. scoparium), and Alaska huckleberry (V. alaskaense). Dwarf bramble (Rubus lasiococcus), and prince's pine (Chimaphila umbellata) also occurs commonly in this type.

Beargrass (Xerophyllum tenax) is the dominant herb in most places. Other associated herbs are: sidebells pyrola (Pyrola picta), beadlily (Clintonia uniflora), and sickletop pedicularis (Pedicularis racemosa).

Landscape Setting. In the Cascade Range mountain hemlock occupies the elevation zone between the true fir dominant montane forests, and the alpine parkland forest types. Mountain hemlock also occurs as high elevation savanna in pure clumps or mixed with whitebark pine in the volcanic soils of the southern Cascades.

References. Atzet et al. 1996, Hemstrom et al. 1987, Volland 1985, Crawford et al. 1999, Johnson and Simon 1987