Montane Forests

Ponderosa pine forest in Cedar Grove, Kings Canyon National Park, after a fire
Ponderosa pine forest after a fire in the Cedar Grove area of Kings Canyon National Park. Fire is an important natural process in Sierra Nevada forests, reducing surface fuels, creating favorable conditions for young trees to establish, and maintaining the open structure of these forests.

Photo by Anthony Caprio

Unlike many of the cone-bearing, evergreen forests of the world, which are dominated by a single species of tree, the mixed-conifer montane forests that cloak the lower and middle slopes of the Sierra Nevada are remarkably diverse. Here ponderosa pine, incense-cedar, white fir, sugar pine, and scattered groves of giant sequoia intermix and coexist. These trees, many of which reach tremendous heights, form some of the most extensive stands of old-growth coniferous forest that remain in the world.

 
Giant sequoias displaying bark charring at base from fire
The charring on the bark of these giant sequoias is from both recent prescribed burning and older fires. The thick bark of giant sequoias protects them from the heat of fires, and although some of the bark is burned, most of it typically remains intact.

Photo by Linda Mutch

The iconic giant sequoias grow interspersed with other trees in a mixed-conifer forest. These include white fir, sugar pine, incense-cedar, red fir, and ponderosa pine. While giant sequoias dominate in terms of size and volume, they are outnumbered by other types of trees. Giant sequoias are the world's largest trees when measured by volume, and can live to be over 3,200 years old. They have a limited distribution, reflecting climatic patterns of the past several thousand years. Once more widespread, today they occur naturally only in the Sierra Nevada. In their current range, cold temperatures may have limited their expansion into higher elevations while drought has limited grove boundaries at low elevations. Soil characteristics also are important: Giant sequoias prefer deep, sandy loam soils that are wetter, less acidic, higher in calcium, and lower in nitrogen than soils associated with neighboring conifer forests.

Periodic fire plays an important role in giant sequoia reproduction. It stimulates seed release from cones, exposes mineral soil where the seeds can germinate, sterilizes the soil (killing seedling pathogens), and opens up the forest canopy to allow in enough sunlight for sequoia seedlings to establish and grow.

To learn more about these magnificent trees, visit the Giant Sequoias page. Visit the Giant Sequoias Drought Response page to learn about recent giant sequoia and climate research. If you would like to visit a sequoia grove, go to the Discovering Sequoia Groves page to get introduced to a few of the parks' groves. For information about the two largest trees, visit The General Sherman Tree and The General Grant Tree pages.

 
Red fir forest in Sequoia National Park
Red fir forests are typically shady, cool forests without many plants growing beneath them. While red fir can be interspersed with giant sequoias and white fir, they typically grow at higher elevations in stands where they are the dominant species.
In the upper montane, the mixed coniferous forest is replaced by nearly pure stands of red fir and lodgepole pine. Characterized by deep snow accumulation during the winter months and a dense canopy that limits the amount of sunlight that reaches the forest floor, the red fir forests lack a diverse herbaceous component. Only the most shade tolerant herbs thrive beneath the towering trees. Lodgepole pines have an unusual distribution, growing in both moist lowlands and in drier sites on benches and ridges. In wetter sites, these forests can support a rich assortment of herbs and wildflowers in their understory.

 
Pine mortality after drought in Sequoia National Park.
View of dead conifers from Beetle Rock, Sequoia National Park, Fall 2015. Four years of drought coupled with higher than average temperatures and mountain pine beetles contributed to extensive tree mortality in the lower mixed-conifer forest.

USGS photo by Nate Stephenson

Threats

Loss of historic fire frequency: Much of the montane forest zone is at risk of severe fire due to departure from its natural fire cycle. The giant sequoia forest type is furthest from its historic fire frequency.

Air pollution: Ozone causes injury to pines, particularly along the western edge of Sequoia National Park where exposure to ozone pollution is greatest. Nitrogen deposition along the western edge of both parks is a concern. Current nitrogen levels have potential to change the species composition, growth patterns, and nutrient cycling, altering the food sources for plants and animals that depend on forests.

Non-native pathogen: White pine blister rust has been a factor in increased sugar pine mortality especially in the Kaweah drainage of Sequoia National Park.

Climate change: Regional warming is implicated in the near doubling of annual tree-mortality rate measured in Sequoia National Park between 1983 and 2004. Recent years of severe drought in addition to higher than average temperatures, increased mountain pine beetle activity, and large wildfires have resulted in millions of pines dying across the Sierra Nevada.

Last updated: September 8, 2017

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