Summit Outside: Understanding lodgepole pine forests
The lodgepole pine is found on high mountain slopes at elevations above 6,000 feet and is typical of the upper foothills, in the wettest parts of the eastern slope and on western slopes in fire regenerated locations.
This is a predominant species in Summit County. Depending on subspecies, the lodgepole pine can grow as an evergreen shrub or tree. The shrub form is stunted when it grows near timberline and is approximately 3.3-9.8 ft. high. The tree form can grow to 130-160 ft high.
Lodgepole pine forests develop in areas that have been cleared either by human activity, like in our region by miners, or as a result of fire. Lodgepole pines require fire to clear out the forest since its cones only open in the heat of a fire, and it is one of the first trees to appear after a fire. Its serotinous cones do not open at maturity because they are sealed shut by a resinous bond between the cone scales. Serotiny is an ecological adaptation exhibited by some seed plants, in which seed release occurs in response to an environmental trigger, which in the case of the lodgepole pines is fire.
These cones remain on the tree for years and require temperatures between 113 and 140 degrees F to melt the resin and release the seed. Only forest fires generate temperatures of this magnitude within a tree’s crown. The bark of the lodgepole pine is fairly thin, minimizing the defense the tree has to fire.
The way that these stands regenerate is they self thin, or out compete with each other leaving dead trees in the stand. These dead trees often fall and become a dry ladder fuel to accelerate the fire to the crown of the tree. When the fire reaches the crowns of the trees, it can jump from tree to tree.
The fire regime for this species is primarily driven by climate and fires occur most often after years of drought. Since the pine forests germinate during the same time frame, the entire stand will often appear to be the same height.
Without fires, the natural progression and germination of younger trees is suppressed and that is why, in fire-mitigated areas, there are stands of very old and possibly sickly trees which are more prone to disease. Most of those brown and dying trees in our region are lodgepole pines, killed by a fungus introduced by the pine beetle.
The other ways seeds are released is when birds like the crossbill or pine squirrels physically open the cones to release seeds. The red or pine squirrels in particular, hoard seeds in compost piles or middens on the ground, and a few seeds fall in ideal locations and conditions and germinate thus producing new trees. In many areas of severe, “beetle-killed” trees you will see living, young lodgepole pines.
The lodgepole pine is tall, straight and slender with very few branches along the lower part of the trunk. The open characteristic of lodgepole pine forests allow a habitat of diverse mixture of plants and animals beneath.
Because the canopy is quite open, allowing sunlight during the early stages of growth, many other plants share the available light.
White spruce will often sprout below because they are more tolerant of shade than the pines, and they will eventually take over if a forest fire doesn’t interrupt the process. Aspen are another fire-adapted species that intermixes with the lodgepole pine.
Another distinguishing feature of the lodgepole pine is that the needles are in pairs on short shoots and rotated about the shoots’ longitudinal axes. The dark and mostly shiny needles are pointed and 1.6 to 3.1 in. length and 0.035 -0.079 in. width. The needle edge is weak to clearly serrated.
The egg-shaped growth buds are reddish-brown and between 0.79 and 1.2 in long. They are short pointed, look slightly rotated and very resinous. Spring growth starts in the beginning of April and the annual growth is completed by early July.
Both male and female cones are found on the same tree, but male cones are in large, orange-red clusters, and the seed cones (female cones), are yellow-brown in color and about 1 in. in length. The tips of the cone scales have sharp prickles, while the tips of the basal scales are usually knoblike.
The straight nature of the lodgepole pine made good Native American tepee poles, hence the name lodgepole.
A typical tepee is constructed with 15-18 lodgepole pines. The long, straight and lightweight characteristics of the species also made it ideal for transport in nomadic buffalo hunting cultures.
Tribes made long journeys across the plains to secure lodgepole pines that only grew in mountainous areas and used horses to drag the poles.
Native peoples also ate the layer inside the bark or cambium and used the sap for medicinal purposes.
Lodgepole pine is used for building cabins, telephone poles, and fence poles.
There is an abundance of dead beetle-killed lodgepole pines in our area and all over western United States and Canada. The beetles kill larger trees over 80 years old, with an average diameter of more than 8 inches. Because of this, there is a whole industry that has evolved from the dead pines. It is called by the catchy name of “denim pine”, or blue-stained pine wood.
The strength and characteristics of the wood is apparently not affected by the fungus, and it is safe to use. In fact there are technical reports that show that the blue stain actually provides beneficial changes to dimensional stability and permeability of the wood. The wood is milled into lumber or used for log homes. Many people actually consider the blue stain attractive. Function from adversity!
Breckenridge resident Dr. Joanne Stolen is retired from teaching microbiology Rutgers University, and has taught classes at CMC. She is now pursuing a career in art, specializing in nature and many of the animals she writes about. Her work can be seen locally.
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