Lodgepole pine forest
If you’re a homeowner, there’s nothing good about forest fires. But it may come as a surprise to learn that for some species, they’re essential. And one of them is the flagpole-shaped tree known as the Rocky Mountain lodgepole pine.
THE SKINNY ON LODGEPOLE PINES
If you’re a skier, you’re probably already familiar with the lodgepole pine. The tall, slender tree often serves as a repository for underwear tossed from the ski lifts. A common sight at higher elevations, the pines pierce the slopes like pencils, while towering over other plants in the landscape.
According to the USDA Forest Service, the lodgepole pine is one of the most widely distributed tree species in western North America. The Rocky Mountain variety, Pinus contorta latifolia, grows in northwest Canada, the Black Hills of South Dakota and as far south as Colorado, central Utah and eastern Oregon.
Distribution map of the Rocky Mountain lodgepole pine
One look up the mountain and you can’t miss them blanketing the slopes in pure, dense stands. Lodgepole pines don’t leave much room for other species. In fact, their slender, reddish brown trunks are packed so tightly together that their lower branches self-prune as they grow. As a result, they tend to develop thin, narrow crowns of stiff, yellow-green needles.
Still, despite their impressive heights of 150′ or more, lodgepole pines seldom attain large diameters. In Utah, for example, some 50′ trees have diameters that measure just around 5 inches. Typically, lodgepole diameters rarely reach more than 16 inches. Yet most trees enjoy a lifespan of 150 to 200 years, with some living for over 400.
IT’S ALL ABOUT THE CONES
So why do lodgepole pines like fire? It’s all about reproduction. As the name implies, all conifers reproduce from seeds that are housed in their cones. In the case of Rocky Mountain lodgepoles, the seeds are located in cones on the uppermost branches. The cones can be closed (serotinous) or open (non-serotinous).
Closed cone/Photo credit: Oregon State University Dept. of Horticulture
Open cone/Photo credit: Oregon State University Dept. of Horticulture
Moreover, depending on what has occurred in nature over time, the type of cone may shift from one to the other.
ALL FIRED UP OVER SEROTINOUS CONES
Most lodgepole forests in North America were established because of fire, in particular in the Rocky Mountains. As a result, in areas prone to fires, lodgepole pines typically bear serotinous cones.
Why? Because serotinous cones are covered with a resin seal that must be melted to open. Forest fires provide the high temperatures the cones need, triggering them to open and release their seeds.
HOW FIRE CREATES LODGEPOLE FORESTS
Lodgepole pines are generally known as prolific seed producers. In fact, some lodgepole pines can produce up to 9,000 cones in a single growing season. As a result, the thin-barked tree’s susceptibility to fire enables it to release vast amounts of seeds.
That being said, the trees may have to wait a long time for a fire, leading to a large accumulation of seeds. Indeed, it’s not uncommon for multiple years’ worth of cones to build up on a tree. Luckily for the species, though, the average serotinous cone can remain on the tree for about 15 years, with some lasting for more than 30.
Rocky Mountain National Park
In addition to unsealing its cones, fire creates the perfect soil for lodgepole seedlings. Soils left behind by fire are rich in minerals and organic matter and the winged seeds settle easily into these freshly-prepared beds. As a result, lodgepole pines can develop huge stands with great density.
New lodgepole pines establishing after fire
And with each new forest fire, the stands regenerate new stands and the cycle continues.
DID YOU KNOW?
The name ‘lodgepole’ refers to the use of the wood in teepees and lodges by native American people. Today, the tree is still a highly desirable source of timbers for rail fences, barns structures and log cabins.
Fence made from lodgepole timbers