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Limber Pine Communities



Status and Trends of Limber Pine Communities: The range of limber pine partially overlaps with that of whitebark pine, both species have large, bird-dispersed seeds, and both are highly susceptible to white pine blister rust, an exotic fungus. The two species are so similar in appearance it is only possible to distinguish between them when cones are present, yet they are more distant taxonomically than other species which are visually dissimilar. While whitebark pine has begun to receive research and management attention in recent years, little is known about limber pine communities.

Limber pine is a 5-needled pine widely distributed in the mountains and foothills of the western United States and southern Canadian Rocky Mountains. Little is known about limber pine ecology and condition. Studies of whitebark pine in Glacier National Park, MT, led to concern about the high amount of mortality in limber pine stands. Like its cousin whitebark pine, it is highly susceptible to white pine blister rust. In 1995 and 1996, site characteristics, tree status and damaging agents were recorded in 81 limber pine stands extending from southern Alberta to eastern Idaho and northern Wyoming. Sampling was far from comprehensive but the results were consistent with the general pattern of limber pine tree status in this region. Limber pine mortality and blister rust patterns in the intermountain west of the US and Canada are documented in Kendall 1997, Kendall and Schirokauer 1997, Kendall et al. 1996c, Kendall 1994 and Kendall and Arno 1990.

In the areas sampled, limber pine occurred on extremely xeric sites at lower and upper tree line. Lower treeline stands were usually found in areas too dry for ponderosa pine, such as the east slopes of the Beartooth Plateau and various island mountain ranges. Pure stands of limber pine were commonly located on windswept, rocky ridges, whereas mixed stands were more common on hillsides, usually with south-facing slopes. Occasionally, mixed stands of limber pine and ponderosa pine, Douglas fir, or lodgepole pine were located on slopes with northern aspects where soil moisture was higher. Whitebark pine was mixed with limber pine in many stands sampled on the Blackfoot Indian Reservation and east side of Glacier National Park in Montana.

Limber pine has suffered extensive, heavy mortality and blister rust infection in northwest Montana and southern Alberta (Table 1). On average, over a third of the limber pine is dead and about 75% of the remaining live trees are infected with rust and 30% of the crown has been lost. Limber pine is functionally extinct or endangered in most of the Greater Glacier Ecosystem, but its health improves somewhat to the north and south. Mortality and blister rust incidence rates were lower north of Waterton Lakes in the Porcupine Hills, Alberta. In southwest Montana, northwest Wyoming, and adjoining areas of Idaho, limber pine mortality and incidence of rust is low to moderate with a few hot spots of heavy infection. Although blister rust incidence in limber pine stands in the Bighorn Mountains of north-central Wyoming is generally low, high infection rates and significant mortality was found at sites in the northeast and southwest corners. We found no rust in Craters of the Moon National Monument in southern Idaho. When trees identified as "probably infected" were included, rust infection rates rose for all areas, sometimes substantially, as in the Porcupine Hills (Table 1).

Not all damage to limber pine trees was attributed to blister rust. In some stands with dead and dying trees or trees with thinning crowns or dead tops, we saw no definite cankers or other evidence of rust. Some of the defoliation was due to limber pine needle cast but a number of factors, such as severe climatic events, mistletoe, and/or mountain pine beetles, may have combined to cause the poor health observed.

Whitebark pine seeds are a well documented bear food but reports of bears feeding on limber pine seeds are scarce. We found evidence that bears ate limber pine seeds in the Porcupine Hills (2 scats) and in Waterton Lakes National Park, Alberta (1 scat). The scats were found in limber pine stands with no whitebark pine trees in the vicinity. Many limber pine trees we surveyed were short enough that bears could reach cones without climbing trees. Thus, limber cones were available to grizzly bears (poor climbers) without squirrels acting as intermediaries by cutting down cones.

Table 1. Preliminary data on the status of and effect of blister rust on limber pine (Pinus flexilus) stands sampled in 1995–96.

Area sampled Number of sample sites Mean Mortality %1

Mean Definite infection %

Mean Probable infection %2

Mean crown kill %3

Bighorn Mtns., WY 4 2








Blackfoot Reservation, MT 6 42








Central Idaho 2 0 0 0 0
E. Front, MT 2 21








N.W. Wyoming 13 10








Porcupine Hills, Alberta 4 14








Grand Teton National Park, WY 1 16 32 32 6
Glacier National Park, MT 22 39








Yellowstone National Park, WY, MT, ID 3 28








Gallatin NF, MT 4 37








S.W. Montana 11 19








Waterton L. National Park, Alberta 8 46








1 Includes mortality from all causes.

2 Includes trees which were probably, as well as, definitely infected with blister rust.

3 Average crown kill of all live limber pine trees.


Katherine Kendall kkendall@usgs.gov


USGS Building, c/o Glacier National Park

West Glacier, Montana 59936-0128


Katherine Kendall


  • Kendall, Katherine C. Limber Pine. Mac, M.J., P.A. Opler, C.E. Puckett Haecker, and P.D. Doran, editors. Status and trends of the nations biological resources. 2 Vols. U.S.Dept. of the Interior, U.S. Geological Survey, Reston, VA. 1998. pg. 486. 964 pp.
  • Kendall, K. C. and J. M. Asebrook. 1998. The war against Blister Rust in Yellowstone National Park, 1945-1978. The George Wright Forum 15:(4)36-49. 
  • Kendall, K. C. 1998. Whitebark pine and limber pine status in the Sweetgrass Hills. Nutcracker Notes 9:11. 
  • Kendall, K. C. and D. Schirokauer. Alien threats and restoration dilemmas in whitebark and limber pine communities. Proceedings of the George Wright Society Conference on Research and Resource Management in Parks and on Public Lands. 1997. Vol. 9. pg. 218-225
  • Kendall, K. C., D. Tyers, and D. Schirokauer. 1996. Preliminary status report on whitebark pine in Gallatin National Forest, Montana. Nutcracker Notes 7:19. USDA Forest Service, Intermountain Research Station, IFSL. Missoula, MT. 
  • Kendall, K. C., D. Schirokauer, E. Shanahan, R. Watt, D. Reinhart, S. Cain, and G. Green . 1996. Whitebark pine health in Northern Rockies national park ecosystems. Nutcracker Notes 7:16. USDA Forest Service, Intermountain Research Station, IFSL. Missoula, MT. 
  • Kendall, K. C., D. Ayers, and D. Schirokauer. 1996. Limber pine status from Alberta to Wyoming. Nutcracker Notes 7:23-24. USDA Forest Service, Intermountain Research Station, IFSL. Missoula, MT. 
  • Kendall, K.C. 1994. Whitebark pine conservation in North American national parks. Pages 302-307 in W. Schmidt and F.K. Holtmeier, eds. Proceedings-International workshop on subalpine stone pines and their environment: The status of our knowledge. USDA Forest Service, Intermountain Research Station, Ogden, UT. General Technical Report INT-GTR-309.
  • Kendall, K.C. and S.A. Arno. 1990. Whitebark pine -- An important but endangered wildlife resource. Proc. Whitebark Pine Symposium. USDA Forest Service General Tech. Rep. INT-270. Pg. 264-273.
limber pine communities, Pinus albicaulis, Pinus flexilis, population trends, whitebark pine communities
Alberta and British Columbia, Canada, Glacier National Park, MT, Grand Teton National Park, Montana, Waterton Lakes National Park, Wyoming, Yellowstone National Park



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Content Information Contact: kkendall@usgs.gov