Anyone who has visited Old Faithful in Yellowstone National Park has encountered lodgepole pine. It may not be elegant, but lodgepole pine is perhaps the most adaptable tree in North America. Besides occupying all but the northern portion of Yellowstone National Park, lodgepole pine can be found on the Oregon coast, in the Sierra de Juarez Mountains of Baja, Mexico, and in Yukon Territory, Canada. In Washington, lodgepole pine is abundant on the east side of the Cascades at upper elevations. Lodgepole can be found growing on dry sandy soils, and in squishy wet meadows. There are five subspecies, which in part explains the tree's wide range. That the scientific name is at odds with the common name is an expression of the differences in where and how the tree grows. The scientific name Pinus contorta is inspired from the coastal form which is frequently "contorted" by the wind. The common name lodgepole is inspired by the interior subspecies which grows tall and straight, and was used as teepee poles by Native Americans.
Lodgepole pine can survive low intensity surface fires fueled by light materials like grass. Crown fire is more typical in lodgepole pine forests, and the trees do not survive, as the bark is very thin. That fire opens the cones of lodgepole pines by heating the resin that holds the cones together, spilling the seeds- a condition known as serotiny, is well known. However, serotinous cones are not at all universal. Trees in the Sierra Nevada of California do not produce serotinous cones, and in Oregon the characteristic is uncommon. Where serotinous cones occur most often is in the Rocky Mountains, where resides the subspecies Pinus contorta latifolia. Within a single tree there may be both ordinary and serotinous cones. By having cones that open seasonally, the tree has the ability to reproduce between fires. By having serotinous cones, chances are at least some seeds remain un-burned to start the next generation of trees, following a stand replacing fire. The post fire environment offers abundant sunlight and mineral soils which is preferred by lodgepole pine for regeneration. The tree can succeed in nutrient poor sites, that result after high intensity wildfires. Once established, the next generation of lodgepole pines begin producing cones at five to seven years of age, resulting in quick establishment of stands. Mature lodgepole pine forests produce thousands of cones with seed production reaching 300,000 per acre.
Because of its ability to reproduce early and abundantly following fires, pure stands of lodgepole pine often occur. Commonly trees grow very close together in a condition popularly known as "dog hair". In over-crowded stands trees are spindly and put on poor growth. Over time weak trees die and disturbance mechanisms including insects, disease, wind and snow load work to reduce the number of trees. The mix of live and fallen dead trees can be a prescription for a hot fire that kills all of the trees and things start over. The second time around the spacing may be more favorable, as there is less seed.
Lodgepole pine can live to be over three hundred years old, but seldom does. Typically, at eighty to one hundred years of age, and eight inches in diameter, lodgepole stands are attacked by bark beetles, particularly the mountain pine beetle. Bark beetles are about the size of a grain of rice, but they can attack by the hundreds. The defense against bark beetles is to squirt pitch to trap the beetles in the sticky substance. This strategy fails when the beetles are too numerous. Beetles burrow through the bark, inoculating the trees with a fungus they carry in their mouth known as blue stain, and laying eggs in an arrays known as galleries. Beetle larvae tunnel under the bark feeding on the cambium and the phloem, which is made more palatable by the blue stain fungus. In recent years, mountain pine beetle epidemics have killed millions of acres of lodgepole pine forests across western Canada and the United States. That these epidemics are so large has to do with the continuity of trees that can be considered ripe for taking, exacerbated by climate change. Shorter, warmer winters means more survival of larvae over winter, and a longer season in which to grow and turn out another generation.
Lodgepole pine is usually accompanied by other conifers. In the early years after a fire it may compete with Douglas-fir and western larch for territory. Later on shade tolerant subalpine fir, pacific silver fir and Engelmann- spruce may come up under a lodgepole canopy and eventually dominate. An alternative scenario is that saplings of subalpine fir sometimes survive crown fires within mature lodgepole stands. Heat is most intense high in the canopy, and the fire may skip over microsite areas at ground level. In this scenario subalpine fir essentially steps around the succession process.
Lodgepole pine is not considered to be one of the more palatable plants for wildlife, however it is an important food for spruce grouse and snowshoe hares in winter. When young lodgepole is tall enough for the trees stick out of deep snow, hares feed on needles. What is good for snowshoe hares is good for lynx a predator of the hares. Black bear, squirrels and porcupines are known to eat the cambium layer of lodgepole pine. Quite a few mammal and bird species eat the seeds, most notably red crossbills. Beetle attacked trees are targeted by woodpeckers that go after larvae. While lodgepole pine trees offer something in the way of food for wildlife, often stands are so dense that little else grows beneath the trees.
As a forest product lodgepole pine is used for dimensional lumber, veneer, and pulp. The wood is slightly yellow in color, soft and easy to work. At Vaagen Brothers mill in Colville, Washington lodgepole pine is considered to be the second most valuable tree after western larch. Vaagen makes studs, and ships the wood waste off to a plant that makes ice cream cartons. Often lodgepole pine has a bizarre deformity that is problematic for lumber, but has a decorative application. Western gall rust causes a softball size canker to grow on the trunks and limbs. These cankers make for interesting stair railing posts, and furniture. They can be seen at Old Faithful Lodge. From a forestry perspective, the challenge with lodgepole is not one of having too few trees, but rather having too many. They need to be thinned either naturally or by human hands if they are to grow into merchantable wood.
Primary source material: Lotan, James E. and Critchfield, Willam B. 1990, Lodgepole Pine, in USDA Forest Service Handbook 651, Volume 1, Conifers.
Technical review: Constance J. Mehmel, Forest Entomologist, Okanogan-Wenatchee National Forest.