This forested system is widespread in upper montane to subalpine zones of the Montana Rocky Mountains, and east into island ranges of north-central Montana and the Bighorn and Beartooth ranges of south-central Montana. These are montane to subalpine forests where the dominance of lodgepole pine (Pinus contorta) is related to fire history and topoedaphic conditions. In Montana, elevation ranges from 975 to 2,743 meters (3,200-9000 feet). These forests occur on flats to slopes of all degrees and aspect, as well as valley bottoms. Fire is frequent, and stand-replacing fires are common. Following stand-replacing fires, lodgepole pine will rapidly colonize and develop into dense, even-aged stands. Most forests in this ecological system occur as early- to mid-successional forests persisting for 50-200 years on warmer, lower elevation forests, and 150-400 years in subalpine forests. They generally occur on dry to intermediate sites with a wide seasonal range of temperatures and long precipitation-free periods in summer. Snowfall is heavy and supplies the major source of soil water used for growth in early summer. Vigorous stands occur where the precipitation exceeds 533 millimeters (21 inches). These lodgepole forests are typically associated with rock types weathering to acidic substrates, such as granite and rhyolite. In west-central Montana ranges such the Big Belts and the Rocky Mountain Front, these forests are found on limestone substrates. These systems are especially well developed on the broad ridges and high valleys near and east of the Continental Divide. Succession proceeds at different rates, moving relatively quickly on low-elevation, mesic sites and particularly slowly in high-elevation forests such as those along the Continental Divide in Montana.
forest and woodland, acidic, shallow ustic soils, organic A horizon greater than 10 cm, Pinus contorta
These forests are dominated by lodgepole pine with shrub, grass, or barren understories. At montane elevations east of the Continental Divide, lodgepole pine stands succeed to Douglas-fir (Pseudotsuga menziesii) forests. In western Montana, there are a number of commonly occurring tree species in later seral stages, including Douglas-fir, western larch (Larix occidentalis), western white pine (Pinus monticola), western red cedar (Thuja plicata), grand fir (Abies grandis) and western hemlock (Tsuga heterophylla). In the subalpine zone, Engelmann spruce (Picea engelmannii), subalpine fir (Abies lasiocarpa) and mountain hemlock (Tsuga mertensiana) commonly succeed lodgepole pine following stand mortality (Pfister et al.,1977). In the productive habitats of western Montana, lodgepole pine stands often decline in a wave of mortality, usually before they are 120 years old.
The shrub stratum may be conspicuous to absent. Common species include bearberry (Arctostaphylos uva-ursi), snowbrush ceanothus (Ceanothus velutinus), twinflower (Linnaea borealis), creeping Oregon grape (Mahonia repens), antelope bitterbrush (Purshia tridentata), birch leaf spiraea (Spiraea betulifolia),Canadian buffaloberry (Shepherdia canadensis), dwarf huckleberry (Vaccinium caespitosum), grouse whortleberry (Vaccinium scoparium), mountain huckleberry (Vaccinium membranaceum), snowberry (Symphoricarpos species) and currant (Ribes species).
Herbaceous layers are generally sparse, but can be moderately dense, and are typically dominated by perennial graminoids such as Columbia needlegrass (Achnatherum nelsonii), pinegrass (Calamagrostis rubescens), Geyer’s sedge (Carex geyeri), Ross’ sedge (Carex rossii), California oatgrass (Danthonia californica), blue wildrye (Elymus glaucus), and Idaho fescue (Festuca idahoensis). Common forbs include yarrow (Achillea millefolium), arnica (Arnica spp.), American pathfinder (Adenocaulon bicolor), queen’s cup beadlily (Clintonia uniflora), silky lupine (Lupinus sericeus) and beargrass (Xerophyllum tenax). Saprophytic species such as coralroot orchid (Corallorhiza spp.), Indian pipe (Moneses uniflora), pinesap (Monotropa hypopithys), and pinedrops (Pterospora andromedea) are often associated with lodgepole pine forests.
Lodgepole pineis an aggressive colonizer and shade-intolerant conifer which usually occurs in lower subalpine forests in the major ranges of the western United States. Establishment is episodic and linked to stand-replacing disturbances, primarily fire. Historically, the frequency of fires varied between 50 and 400 years and their severity resulted in a diverse mosaic of age classes and species mixtures. In the Northern Rockies, severe fires typically have created large expanses of even-aged, pure or mixed species stands of lodgepole pine. Trees with closed, serotinous cones appear to be strongly favored by fire, and allow rapid colonization of fire-cleared substrates (Burns and Honkala, 1990). The incidence of serotinous cones varies within and between varieties of lodgepole pine, but is most prevalent in Rocky Mountain populations. Lodgepole pinestands exhibiting a multi-aged population structure, with regeneration occurring, exhibit a higher proportion of trees bearing non-serotinous cones. Trees with non-serotinous cones may predominate in persistent or climax Rocky Mountain lodgepole pine forests. If serotiny is expressed in these stands, cone polymorphism exists and allows regeneration after non-fire disturbances.
In fire-generated stands of similar age, trees become susceptible to mountain pine beetle (Dendroctonus ponderosae) and lodgepole pine dwarf mistletoe (Arceuthobium americanum) infestations at approximately the same time, resulting in large-scale infestations and mortality. In this system, very large scale, stand-replacing fires have occurred frequently throughout Montana during the past 20 years.
Large, prescribed and natural, stand-replacement fires have occurred in forests with high mortality from mountain pine beetle and dwarf mistletoe infestations. Restoration strategies will depend largely on fire severity. Under favorable moisture conditions, seeds released from serotinous cones during the fire germinate on exposed mineral soil and disturbed duff the following spring. Fire creates a favorable seedbed by removing loose organic matter and exposing mineral soil or decomposed organic matter, which encourages germination. Therefore, in light or moderately severe fires, additional restoration practices are not required. Early successional stages following fire in lodgepole pine forests are dominated by an understory of forbs and to a lesser extent, graminoids such as fireweed (Chamerion angustifolium), aster (Aster species), nettleleaf giant hyssop (Agastache urticifolia), and pinegrass (Calamagrostis rubescens).
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