More info for the terms: association, cover, mesic, serpentine soils, ultramafic soils, xeric
Beargrass is widely found as a understory dominant in cool western
spruce-fir forests. It is also common under alpine larch (Larix
lyallii) and whitebark pine (Pinus albicaulis)-subalpine fir stands on
cold, rocky sites at upper timberline [7,34]. It is less common below
the subalpine zone [56]. Common understory dominants growing with
beargrass are huckleberries (Vaccinium spp.), grouse whortleberry
(Vaccinium scoparium), and sedges [22,18].
Rocky Mountain sites: At the northeastern limit of its range in
Waterton Park, beargrass is found on moderate to steep south-facing
slopes on colluvial and morainal landforms with Engelmann spruce (Picea
engelmannii), subalpine fir, and whitebark pine [1,67]. Beargrass is
dominant with menziesia (Menziesia ferruginea) in subalpine forests near
the border between the United States and Canada [19]. Although they
grow together, beargrass favors more xeric conditions than does
menziesia [63]. In northern Idaho beargrass grows predominantly on
ridges and the upper portions of slopes [22,69]. Pure stands of
beargrass are found in treeless open parks with summer-dry soils on high
ridges and southerly slopes in northern Idaho and eastern Washington
[21]. In northern Idaho western redcedar (Thuja plicata) stands,
beargrass is most common at higher elevations [40]. In Montana,
beargrass may extend slightly from the forest into adjacent grasslands
[76].
West Coast sites: In the Coastal Mountains of Oregon, beargrass is
found on steep sites on well-drained, frequently shallow, soils on
rugged, rocky topography near ridgetops [50]. It is often in areas with
active sheet erosion [50]. In the Oregon Cascades it may be dominant on
cold dry ridges and mountain tops from 4,700 to 5,800 feet (1,433-1,768
m) with soils that are poorly drained in spring and excessively well
drained in summer. These sites often show no sign of having been
previously forested, but this community could be a prolonged seral stage
[49]. While beargrass grows on most sites in the western hemlock zone
of Oregon, Washington, and northern California, it has higher cover on
drier sites and grows well on talus or scree slopes [30,34,77]. In the
silver fir zone it does best toward the xeric end of the moisture
gradient [30]. Understories on relatively dry silver fir and mountain
hemlock sites may be depauperate with little growing besides beargrass
and huckleberry [33,34]. In Oregon's subalpine fir zone it does best on
upper south slopes and ridges [34]. Beargrass is common in the
mixed-evergreen and mixed-conifer zones on relatively cool, dry sites
under Douglas-fir (Pseudotsuga menziesii), grand fir, incense-cedar
(Libocedrus decurrens), sugar pine (Pinus lambertiana), tanoak, golden
chinquapin (Chrysolepis chrysophylla), and California black oak (Quercus
kelloggii) in southern Oregon, northern California, and the Siskiyou
Mountains [12,34,77]. In the pygmy forest region of California, it
grows in stands of Bishop pine (Pinus muricata) and Bolander pine (P.
bolanderi) [88]. Westman [88] considers beargrass a heliophilic
(sun-loving) plant which does well on these relatively unproductive,
open sites.
Soils: Beargrass grows on a variety of soils and is able to grow well
on very shallow or rocky soils [30,43]. It does well on basaltic lava
flows in southern Washington but does not grow well on pumice [33,34].
On serpentine soils in the Siskiyou Mountains of Oregon and California,
beargrass grows most vigorously on submesic to mesic sites, while on
olivine gabbro soils, it is found on xeric to subxeric sites [89]. In
the Siskiyous it is the most useful indicator of small serpentine
outcrops [89]. It may dominate the herbaceous layer on serpentine and
other ultramafic soils under Douglas-fir, western white pine,
Port-Orford-cedar (Chamaecyparis lawsoniana), Jeffrey pine (Pinus
jeffreyi), huckleberry oak (Quercus vaccinifolia), and, at higher
elevations, white fir (Abies concolor) [10,47,89,94]. In Montana it
often occurs in association with volcanic ash soils [71]. In the Garnet
Mountains of Montana, where beargrass is prominent on soils formed from
granite and quartzite, essentially no beargrass occurs on soils formed
from limestone [37]. In Montana growth is poor on gravel, sand, and
dense clay; fair on clay; and good on sandy loam, loam, and clay loam
[27]. Its growth is poor on organic, saline, sodic, and sodic-saline
soils but good on acidic soils [27].
Elevation: Elevational ranges in some western states are [27]:
Minimum Maximum
feet meters feet meters
Montana 5,000 1,524 8,800 2,682
Wyoming 7,200 2,195 7,200 2,195
California sea level 6,000 1,829
