干旱区生态环境知识资源中心

The High Five symposium is devoted to exchanging information about a small group of pines with little commercial value but great importance to the ecology of high-mountain ecosystems of the West. These High Five pines include the subalpine and treeline species-whitebark (Pinus albicaulis), Rocky Mountain bristlecone (P. aristata), Great Basin bristlecone (P. longaeva), and foxtail (P. balfouriana)-the montane to subalpine pine, southwestern white (P. strobiformis), and the lower treeline to upper treeline pine, limber (P. flexilis). Here, we discuss the taxonomy, distribution, ecology, and Native American use of these pines, as well as current threats and conservation status. Traditional classification places the bristle cones and foxtail pine together in Subsection Balfourianae, limber and southwestern white pine in Subsection Strobi, and whitebark pine in Subsection Cembrae. Whitebark pine has the largest range and most northerly occurrence. The distribution of limber pine is also large, with a wide elevational range. Southwestern white pine occurs from the southwestern U.S. through northern Mexico; fox tail pine is found in two widely-separated regions in California; and, Rocky Mountain bristlecone pine occurs in northern Arizona and the southern Rocky Mountains. Great Basin bristlecone pine is restricted to the high desert ranges of eastern California, Utah, and Nevada. The High Five pines vary successionally and geographically from minor to major forest and treeline components. As a group, they are also moderately to strongly shade intolerant, and dependent on disturbance, particularly fire, on productive sites for forest renewal. The high elevation pines tolerate cold, arid sites with poor soils. On exposed sites with infrequent disturbance, these trees can live for 1000 to 4500 years, depending on the species. Thus, these pines together comprise geographically extensive and ecologically diverse forest habitat types. Whitebark, limber, and southwestern white pine produce large, wingless seeds that are eaten by a diversity of wildlife. Clark's nutcrackers (Nucifraga columbiana) are important seed dispersers for whitebark and limber pine, for southwestern white pine in its northern range, and to a lesser extent for the bristlecone pines. Furthermore, the High Five pines provide important ecosystem services directly benefiting humans, including the use of the seeds and other parts of pines as food and medicines by Native Americans, the regulation of downstream flow and the prevention of soil erosion by treeline forests, and the aesthetic and spiritual values often associated with high elevation forests. The future survival of the High Five pines is threatened by the exotic blister rust pathogen Cronartium ribicola, current mountain pine beetle (Dendroctonus ponderosae) outbreaks, successional replacement from fire suppression, and climate change. Whitebark pine has been assigned special status in Washington and British Columbia, and endangered status along with limber pine in Alberta. A petition to list whitebark pine as an endangered or threatened species is currently being evaluated by the U.S. Fish and Wildlife Service. In Canada, whitebark pine has been assessed federally as Endangered and is expected to be legally listed soon under the Species at Risk Act.