FOLBR - Friends Of the Lower Blue River

Sustainable Hiker - Beyond the Trail Series

Colorado’s Diverse Coniferous Forests

Many Coloradans overlook the not-so-subtle differences between the state’s complex mix of coniferous forests. The various tree species, geographical aspects, and weather patterns throughout the state greatly influence how forest lands should be managed. More importantly, how they manage themselves.

Here, in the Blue River Valley, lodgepole pine, spruce and fir dominate the sub-alpine terrain. These forests are extremely dense and do not allow for easy passage by recreational hikers, hunters, and backcountry skiers. As a result, many mistake these forests for being overgrown or poorly managed.

Colorado’s lodgepole pine, spruce, and fir trees have a lifespan of 100 to 150 years. These trees reach a size that makes them highly susceptible to the mountain pine beetle. The beetles require a certain trunk diameter for insulation and food. They target and kill off large mature sections, causing the impassible pile-up of dead trees, familiar to so many of Summit County residents.

If the pine beetle does not get to these sub-alpine forests first, fire will. Due to the relatively high moisture levels in Summit County, fire is a less frequent than at lower elevations. But it is important for healthy lodgepole pine, spruce, and fir forests. These forests rely on fire for the germination of their seeds. After fire passes through the sub-alpine terrain, regeneration is rapid. A one-acre area may have as many as 20,000 standing trees in just a few decades. This natural cycle of growth, beetle-kill, and fire is how the sub-alpine forests in Summit County regulate themselves.

The role of wildfire is what greatly sets apart the Blue River Valley forests from the evergreen forests that cover most of foothills on the Front Range. Historically, the Front Range forests were open, with large, widely dispersed evergreen trees upwards of 500 years old. Grass fires were frequent on the Front Range, occurring at least once every three years. They burn at a low temperature to only kill saplings, while leaving the larger trees unscathed.

When the Front Range was settled in the 19th century, cattle grazing, and wildfire suppression prevented the low-heat grass fires that keep the evergreen forests in balance. Without the grasses to burn, smaller trees were able to grow, leaving us now with dense evergreen forests susceptible to intense and unprecedented fires. As a result, forest management on the Front Range requires more human intervention to thin out terrain, as compared to the sub-alpine forests of the Blue River Valley.

Jackson Beck
FOLBR Board Member

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