Name:
Tsuga heterophylla - Abies grandis - Larix occidentalis Lower Montane Forest Macrogroup
Reference:
NatureServe Biotics 2019
Description:
This macrogroup encompasses mesic conifer forests and woodlands of the lower montane zone of the central Rocky Mountains and interior Pacific Northwest, including the eastern Cascades. <i>Abies grandis, Larix occidentalis, Pseudotsuga menziesii, Thuja plicata</i>, or <i>Tsuga heterophylla</i> are the major dominants. <i>Abies lasiocarpa, Picea engelmannii, Picea engelmannii x glauca</i> hybrids, <i>Picea glauca, Pinus contorta</i>, and <i>Pinus monticola</i> are major associates. <i>Pinus ponderosa</i> may be present but only on the warmest and driest sites. Deciduous hardwood species occur, but typically are not dominant; they include <i>Populus tremuloides</i> and <i>Betula papyrifera</i>. This macrogroup is found in the Rocky Mountains of western Montana west through northern Idaho into northeastern Washington and southern and central British Columbia, and south into the northwestern Blue Mountains of Oregon. Although in a continental climate, these forests are influenced by incursions of mild, wet, Pacific maritime air masses. Snow occurs throughout the macrogroup, but can be modified by warmer Pacific air masses even in the winter, or in the southern range, melted by rain during warm winter storms. Elevations range from 100 to 2195 m (300-7200 feet). In the Cascades, this macrogroup occurs on the upper east slopes in Washington, south of Lake Chelan and south to Mount Hood in Oregon. Occurrences are generally found on all slopes and aspects but grow best on sites with high soil moisture, such as valley bottoms, on benches, well-drained slopes, toeslopes and moist ravines. Sites supporting these forests are typically warmer and moister than the prevailing local climate. However, these are moist, non-flooded or upland sites that are not saturated year-long. At the periphery of its distribution, this macrogroup is confined to moist canyons and cooler, moister aspects. These mesic and productive forests tend to have long fire-return intervals, ranging from 150 to over 500 years for stand-replacing fires, and with moderate-severity fire intervals of 50-100 years. Gap dynamics are important in older stands. Disturbance regimes are not well-documented for the montane white spruce forests, but likely include periodic windthrow as well as fire spreading from adjacent, drier forests and woodlands. <i>Larix occidentalis</i> woodlands are maintained post-establishment by frequent, low-severity surface fires.
Accession Code:
urn:lsid:vegbank.org:commConcept:40800-{17151DA2-A0B7-4045-90E8-184A5BD09D8B}
Plot-observations of this Community Concept:
0
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