Rocky Mountain Lodgepole Pine Forest

This ecological system is widespread in upper montane to subalpine elevations of the Rocky Mountains, Intermountain West region, north into the Canadian Rockies and east into mountain "islands" of north-central Montana. These are subalpine forests where the dominance of Pinus contorta is related to fire history and topo-edaphic conditions. Following stand-replacing fires, Pinus contorta will rapidly colonize and develop into dense, even-aged stands. Most forests in this ecological system occur as early- to mid-successional forests which developed following fires. This system includes Pinus contorta-dominated stands that, while typically persistent for >100-year time frames, may succeed to spruce-fir; in the southern and central Rocky Mountains it is seral to Rocky Mountain Subalpine Dry-Mesic Spruce-Fir Forest and Woodland (CES306.828). More northern occurrences are seral to Rocky Mountain Subalpine Mesic-Wet Spruce-Fir Forest and Woodland (CES306.830). Soils supporting these forests are typically well-drained, gravelly, coarse-textured, acidic, and rarely formed from calcareous parent materials. These forests are dominated by Pinus contorta with shrub, grass, or barren understories. Sometimes there are intermingled mixed conifer/Populus tremuloides stands, with the latter occurring with inclusions of deeper, typically fine-textured soils. The shrub stratum may be conspicuous to absent; common species include Arctostaphylos uva-ursi, Ceanothus velutinus, Linnaea borealis, Mahonia repens, Menziesia ferruginea (in northern occurrences), Purshia tridentata, Rhododendron albiflorum (in northern occurrences), Spiraea betulifolia, Spiraea douglasii, Shepherdia canadensis, Vaccinium cespitosum, Vaccinium scoparium, Vaccinium membranaceum, Symphoricarpos albus, and Ribes spp. In southern interior British Columbia, this system is usually an open lodgepole pine forest found extensively between 500 and 1600 m elevation in the Columbia Range. In the Interior Cedar Hemlock and Interior Douglas-fir zones, Tsuga heterophylla or Pseudotsuga menziesii may be present. In Alberta, species composition indicates the transition to more boreal floristics, including such species as Empetrum nigrum, Ledum groenlandicum, Leymus innovatus, and more abundant lichens or mosses such as Cladonia spp., Hylocomium splendens, and Pleurozium schreberi.

These forests are dominated by Pinus contorta with shrub, grass, or barren understories. Sometimes there are intermingled mixed conifer/Populus tremuloides stands, with the latter occurring with inclusions of deeper, typically fine-textured soils. The shrub stratum may be conspicuous to absent; common species include Arctostaphylos uva-ursi, Ceanothus velutinus, Linnaea borealis, Mahonia repens, Menziesia ferruginea (in northern occurrences), Purshia tridentata, Rhododendron albiflorum (in northern occurrences), Spiraea betulifolia, Spiraea douglasii, Shepherdia canadensis, Vaccinium cespitosum, Vaccinium scoparium, Vaccinium membranaceum, Symphoricarpos albus, and Ribes spp. In southern interior British Columbia, this system is usually an open lodgepole pine forest found extensively between 500 and 1600 m elevation in the Columbia Range. In the Interior Cedar Hemlock and Interior Douglas-fir zones, Tsuga heterophylla or Pseudotsuga menziesii may be present. In Alberta, species composition indicates the transition to more boreal floristics, including such species as Empetrum nigrum, Ledum groenlandicum, Leymus innovatus, and more abundant lichens or mosses such as Cladonia spp. (= Cladina spp.), Hylocomium splendens, and Pleurozium schreberi.

This system occurs in the upper montane to subalpine elevations of the Rocky Mountains, north into the Canadian Rockies and east into mountain "islands" of north-central Montana. Elevations range from just over 900 m in the northeastern Cascades to well over 3100 m in the Uinta Mountains in Utah and the southern Colorado Rockies. Temperature regimes are extreme throughout this region and frequent growing season frosts occur. Annual precipitation in these montane and subalpine habitats ranges from less than 40 cm to over 150 cm, usually with the majority falling as snow. Late-melting snowpacks provide the majority of growing-season moisture.

Soils are variable but are typically well-drained, gravelly, coarse-textured, acidic, rarely from calcareous parent materials with occasionally inclusions of deeper, typically fine-textured soils. Other stands occur on excessively well-drained pumice deposits, glacial till and alluvium on valley floors where there is cold-air accumulation, warm and droughty shallow soils over fractured quartzite bedrock, and shallow moisture-deficient soils with a significant component of volcanic ash.

Pinus contorta is an aggressively colonizing, 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. The incidence of serotinous cones varies within and between varieties of Pinus contorta, being most prevalent in Rocky Mountain populations. Closed, serotinous cones appear to be strongly favored by fire, and allow rapid colonization of fire-cleared substrates (Burns and Honkala 1990a). Hoffman and Alexander (1980, 1983) report that in stands where Pinus contorta exhibits a multi-aged population structure, with regeneration occurring, there is typically a higher proportion of trees bearing nonserotinous cones.

LANDFIRE developed a state-and-transition vegetation dynamics VDDT model for this system which has five classes in total (LANDFIRE 2007a, BpS 2810500). These are summarized as:

A) Early Development 1 All Structures (20% of type in this stage): Tree cover is 0-80%. Stand initiation: Grasses, forbs, low shrubs and lodgepole seedlings-saplings. This class does not last long; young lodgepole grows fast. If aspen is present, it grows faster and dominates lodgepole. Cover of trees (seedlings-saplings) varies widely.

B) Mid Development 1 Closed (20% of type in this stage): Tree cover is 51-100%. Stem exclusion (RMLANDS: Rocky Mountain Landscape Simulator): Moderate to dense pole-sized trees, sometimes very dense (dog-hair); longest time in this class without disturbance. Aspen usually not present.

C) Mid Development 1 Open (tree-dominated - 20% of type in this stage): Tree cover is 21-50%. Understory reinitiation: Variety of lodgepole size classes, some mature trees, often somewhat patchy. If aspen is present, lodgepole usually dominates it.

D) Late Development 1 Open (20% of type in this stage): Tree cover is 61-100%. Many mature lodgepole pine with closed canopy. Trees may vary in age, but consistent in size, diameters and heights.

E) Late Development 1 All Structures (10% of type in this stage): Tree cover is 31-60%. Many mature lodgepole pine, somewhat patchy, variety of lodgepole size classes, open canopies overall but patches of denser trees. Dead and downed woody materials increasing in volume, young trees infilling openings.

Before fire suppression began in the early 20th century, most fires were low-intensity, creeping, surface fires, whereas most fires today are high-intensity crown fires that occur during severe fire weather (dry and windy) (Lotan et al. 1985). The stand-replacing fire interval in lodgepole pine forests is about 215 years (LANDFIRE 2007a, BpS 2810500).

Nutrient cycling, specifically carbon cycling, is an important ecological process within many ecological systems. Biological decomposition in lodgepole pine forests is more limited than biological production, resulting in accumulation of organic materials, especially in the absence of fire (Harvey 1994).

Threats and stressors to this forest system include altered fire regime, altered stand structure from fragmentation due to roads, logging, mining, or other human disturbances (CNHP 2010). These disturbances can cause significant soil loss/erosion and negatively impact the water quality within the immediate watershed (CNHP 2010). Invasive exotic species can become abundant in disturbed areas and alter floristic composition. Direct and indirect effects of climate change may alter dynamics of indigenous insects such as mountain pine beetle (Dendroctonus ponderosae) and cause a buildup in population size with less extreme winters leading to large outbreaks the can cause high mortality in mature trees.

This system occurs at upper montane to subalpine elevations of the Rocky Mountains, Intermountain West region, north into the Canadian Rockies, and east onto mountain "islands" of north-central Montana. In Washington, this system occurs mostly on the east side of the Cascade Crest. In Oregon, this system only occurs in the Blue Mountains; all Oregon Cascades lodgepole pine forests are included in other systems.