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Community Field Guide

Scientific Name:
Pinus flexilis / Festuca idahoensis Woodland

Common Name:
Limber pine / Idaho fescue Woodland


Photo by S.V. Cooper

Community Description

Summary:
Pinus flexilis / Festuca idahoensis is a small- to large-patch association, probably the most extensive of any type in the Pinus flexilis series. It is restricted to a three state area (and anecdotally attributed to adjacent portions of Alberta) extending eastward from the northernmost portion of the Rocky Mountain Front in Montana (east of Continental Divide) to the individual central Montana ranges and southward to the isolated ranges of central Idaho north of the Snake River Plain. It is also found in northwestern Wyoming ranges, extending to the southeastern extremity of the Wind River Range. It is usually found at lower timberline and may extend both into foothill landscapes at the base of major ranges and occur well into the subalpine zone as a topoedaphic climax. The tree canopy is very open, dominated by Pinus flexilis, though Pseudotsuga menziesii may be equally well represented; the only other tree found on these demanding sites is Juniperus scopulorum. The undergrowth is dominated by the bunchgrasses Festuca idahoensis and Pseudoroegneria spicata. The shrub component, if present at all, consists of very scattered individuals of Ericameria nauseosa (=Chrysothamnus nauseosus), Gutierrezia sarothrae, Juniperus communis or Juniperus horizontalis; early- to mid-seral conditions noted in Wyoming and Idaho may have Artemisia tridentata ssp. vaseyana with at least 10% cover. Forb composition is usually relatively diverse but cover of this component does not commonly exceed 10%.

Environment:
This association, occurring in foothill locations, ranges from flats to gentle- and moderate-slopes of all aspects. In more mountainous terrain across the type’s distributional range Pinus flexilis / Festuca idahoensis is commonly found on west- to south-facing aspects of moderate- to steep-slopes often associated with upper slopes, slope shoulders, ridges and other wind-exposed positions. In Montana the observed elevation range is from 4,800 (at the base of the Rocky Mountain Front) to 8,800 feet in the Ruby Range (in the state’s southwest). The Montana upper elevation limits of the type are inexplicably greater than reported for central Idaho (6,600 to 8,300 feet) or Wyoming (7,700 to 8,500 feet) though in fact the range probably extends to higher elevations in both these states. This association is apparently differentially better represented on calcareous substrates. The amount of exposed surface (soil and rock) usually approaches 20% and has been noted to be as high as 50%. Adjacent drier sites commonly support Festuca idahoensis and Artemisia tridentata var. vaseyana dominated rangeland communities; it regularly grades to Pinus flexilis / Juniperus communis or various Pseudotsuga menziesii dominated associations of moister habitats at lower elevations and to Picea series sites of more mesic upper elevation sites.

Vegetation:
Widely spaced Pinus flexilis dominate the upper stratum in these open, savanna-like, all-aged appearing stands (at least stands not readily accessible to tree harvesting) where total canopy cover usually does not exceed 60%. Pseudotsuga menziesii may be well represented or even co-dominant, but size-class distributions indicate Pinus flexilis will continue to be at least a co-dominant component. Juniperus scopulorum may be well represented as a long-persisting seral species. Undergrowth is dominated by bunchgrasses with Festuca idahoensis, a common indicating habitat moister than those supporting just Pseudoroegneria spicata or Hesperochloa kingii as dominants. In extreme southwestern Montana Hesperochloa kingii is a conspicuous, occasionally dominant, component. Forb diversity is often high with Phlox hoodii, Machaeranthera canescens, Astragalus miser, Senecio canus and Linum perenne being consistently represented. Shrubs commonly found scattered in canopy openings are Juniperus communis, Artemisia tridentata var. vaseyana, Ribes cereum, Gutierrezia sarothrae and Ericameria nauseosa.

Dynamics:
Fire frequency in this type apparently varies with local conditions. Steele et al. (1981) and Pfister et al. (1977) note a low frequency whereas Cooper et al. (1999) found scattered, old (>250 years) fire-scarred individuals (both Pseudotsuga menziesii and Pinus flexilis) with multiple fire-scars indicating a past history of ground-fires. A current concern for this type is stand altering Pinus flexilis mortality due to white pine blister rust. Only stands along Montana’s Rocky Mountain Front are currently being devastated, but the wind borne rust spores have the potential to reach remote populations and the alternate host, Ribes spp., is ubiquitous in or adjacent to any of the environments where this plant association might occur. Lanner and Vander Wall (1980) have documented that populations of this wingless-seeded pine often owe their establishment to the failure of corvid birds to recover their seed caches. The effects of the loss of Pinus flexilis populations (and hence seed source) upon species directly using this resource (corvid birds, squirrels, grizzly bears) is currently unknown; also unknown is the natural rate of resistance in this pine.

Global Rank: G5 State Rank: S5

Community References

Identifier:
CEGL000805

Author:
01-03-14 / S. V. Cooper, MTNHP

Citations:
Johnston 1987, Pfister et al. 1977, Steele et al. 1981, Steele et al. 1983

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This information is from the:
Montana Natural Heritage Program
Montana State Library--Natural Resource Information System
1515 East Sixth Ave., Helena, MT 59620-1800
406 444-5354
http://mtnhp.org
mtnhp@mt.gov