Research on the interactions between fire and living organisms and their environment, known as fire ecology, helps land managers understand how fire burns in different types of vegetation and how organisms respond to fire. In the southern Cascades and the Sierra Nevada mountains, fires have occurred for thousands of years. Fire is as much a part of these ecosystems as are wind, rain, erosion, and volcanic and hydrothermal activity. At Lassen Volcanic, research shows that native plants and animals are well-adapted to fire and some plants will not regenerate well without it.
Many plants and trees are adapted to regenerate after fire. Top to bottom: aspen, green-leaf Manzanita, and a lodgepole pine cone.
Fire Effects on Plants
Fire creates opportunities for plant growth by burning debris on the forest floor and releasing nutrients into the soil. Fire also opens up gaps in the forests, creating more light for tree seedlings, shrubs, and other plants that may not thrive under a shady forest. For trees and shrubs that survive the fire and are not injured, growth may increase from the extra nutrients and light and the reduced competition from plants that died in the fire.
Plants have different adaptations to fire. Some types of trees have thick bark to protect them from fire’s heat, or may have their branches high off the ground, out of reach of the fire. Other plants may die in the fire, but have seeds in the soil or deposit them from cones during or after the fire; many seedlings must establish for a few to survive to adulthood! Other plants may re-sprout from deep roots or the base of their stems. Aspen trees typically sprout back from their network of lateral roots.
Some species of shrubs, like common manzanita, will germinate readily after fire from a soil seed bank, with seeds stimulated to grow by the fire’s heat. Many herbaceous plants may also grow from seeds in the soil, or sometimes re-sprout from deep roots. Conifer trees store seeds in cones, and some species like lodgepole pine have increased seed release after fire. Most pines need open, sunny areas for their seedlings to take root and grow. In forests lacking fire for many decades, shade-tolerant fir trees become more common and may gradually replace pines, which need open, sunny conditions.
Some insects and animals benefit from recently burned forests.
NPS/Mike Laycock
Effects of Fire on Animals
Like native plants, most animals in the park have evolved with fire. Many large mammals like deer and bears may be able to move out of the way or flee a fire. Most small animals such as rodents, amphibians, and reptiles avoid fire by seeking refuge in tunnels or burrows, under large downed logs, or in damp areas such as meadows or streams. But many animals may die in a high-severity fire. Later, wildlife populations re-establish, in parallel with post-fire growth of vegetation.
The burned, dead, and decaying trees, whether fallen as logs or standing upright as snags, are important habitat for insects and various mammals and birds. Birds such as black-backed and Lewis’s woodpeckers, are attracted to burned forests, and will probe burned trees to feed on insects and excavate nest cavities. Other cavity-users that depend on woodpeckers to carve out a cavity may follow—tree squirrels, chickadees, swallows, bluebirds, and kestrels are all examples.
Browsing animals like deer may need to feed in unburned or lightly burned areas initially and return later to take advantage of new growth.
Grazing animals (rodents, ground squirrels, rabbits) and browsers (such as deer) may find more vegetation to feed on as shrubs and other plants thrive in areas made more favorable to plant growth with increased sun and soil nutrients. Even spotted owls, a species favoring old-growth forest, may benefit from more open burned patches where they can hunt for rodents, as long as enough old growth forest remains for them to roost and nest in. While some animals die in a fire, or lose part of a forest they were living in, others will benefit in the longer term from diverse habitats and new growth. More research is needed to better understand the impacts of large, high-severity fires on wildlife.
