Fire Ecology

A ridge of a mountain shows green trees on one side and burned trees on the other with red rocks in the background
Fires often leave behind a patchwork of burned areas, which create diverse habitats for plants and animals.

NPS Photo

 
A purple Russian Thistle grows from under a charred black log
Fire can create opportunities for new life

Forest Succession


A fire sweeps through a forest, leaving behind blackened trees, burnt grasses, charred shrubs, and scattered ash. Though the aftermath may sound desolate, a fire like this creates opportunities for new life. Given time, grasses will start to grow back as their seeds are brought on the wind. Shrubs will regrow from their roots, encouraged by the new nutrients and warmth from the black ash in the sun. Without shade and competition, new trees will sprout up from the ground. Birds and bats will use the remains of burned trees for shelter until the new trees grow tall enough. Other wildlife will also return with the young plants. It may take time, but a forest can recover from a fire in this way, through a process called “succession”.

“Stand-replacing fires” completely reset a forest ecosystem, allowing the succession process to start over from scratch. Historically, these kinds of fires are not common in western forests. At Bryce Canyon, it would be much more common for lightning to start a fire about once every 7-8 years. There was not enough time between these fires for fuel to build up in the same way as it has today, so each individual fire would be less destructive. Rather than burning everything, these fires might only destroy the grasses and shrubs on the forest floor.

The older trees might be singed, but many of them are capable of surviving these kinds of fire. Even so, why would plants or animals choose to live in places that would be dangerous for them?
 

Why are Today's Fires Often so Destructive?

 
Small pink manzanita blooms against the green leaves of the Manzanita plant
Manzanita - one of the shrubs that can be "top-killed" by fire then send up new shoots from the old roots.

NPS Photo

Adaptations to Fire

Grasses

As the smoke clears from a fire, the forest floor is black and barren, covered in ash. Later in the summer, the same breeze that scatters the ashes will carry something else, too: seeds. Many grasses have seeds that travel on the wind. If the conditions are right, those seeds will take root and sprout new grass. The blackened forest floor, with its extra nutrients and heat from the sun, is a perfect home. After a fire, grasses like Indian rice grass are some of the first plants to start growing again. Though grasses themselves are flammable, they help to encourage the cycle of fire, creating a good habitat that they can quickly repopulate.

Shrubs

Amidst the grass, clumps of green leaves emerge from the charred remains of a small bush. Although this bush may have looked dead after the fire, its underground roots were still very much alive. Many shrubs at Bryce Canyon; including greenleaf manzanita, mountain snowberry, and Utah serviceberry; can be “top-killed” by fire. While the fire might destroy the part of the plant above the ground, the roots underneath are protected from the heat. When they are ready, they will send up new shoots from the old roots. This can take some time, and usually happens after the grasses have already come back.

 
diagram of fire moving through a forest
Though ponderosa forests thrive with frequent, low-intensity surface fires, crowded forests lead to more intense crown fires and complete stand replacements.

NPS diagram

 
Color photo: Yellow Aspen trees viewed from below against a blue sky
The roots of Aspen trees will usually survive a fire even if the tree itself does not.

Trees

Around the same time as the shrubs, tiny sapling trees sprout from the ground, leaves trembling in the slightest wind. These are quaking aspen, which will eventually grow into a tall tree with paper-white bark. Just like the shrubs, aspen roots will usually survive a fire even if the tree itself doesn’t. Unlike the shrubs, aspens can have interconnected root systems extending for miles! Quaking aspens are often the first kind of tree to come back after a fire, sometimes even if there weren’t any aspen in the area before the fire. During the fall, it can be easy to tell where a recent fire occurred by the reds and oranges of the aspen leaves covering a slope. Look for them on a hillside along the scenic drive near Rainbow Point, where they are returning after the prescribed Puma Fire in 2008.

Eventually, small trees with needles will start to make their way back into a burned area. Some trees, however, might not have been affected by the fire in the first place. Even after a fire, ponderosa pine trees are often left standing. Tall and sturdy, with reddish-orange bark, the ponderosa pine is one of the most common trees in Bryce Canyon – and for good reason! They are also the most fire-resistant.
 

How do Ponderosa Pines Defend Themselves Against Fire?

 
A stand of blackened, charred trees with white ash covering the ground
Charred ponderosa pines after the Bridge Fire (2009)

Wildlife

Throughout the process of succession, animals continue to thrive off of the resources that are available. In the case of a fire, most animals are able to move out of the area before the fire becomes dangerous. Once the flames are gone, they will begin to move back into the burned area. Birds and bats will often make new homes in the snags, or standing dead trees, created from the fire, finding shelter in the spaces between the burned bark. Herbivores and pollinators will find tasty treats in the new plants and flowers that sprout from the ashes. As the forest regrows, wildlife will continue to return.

If a forest goes years without any ground fires, it will start to change. Young sapling trees will grow tall, their leaves shading the forest floor as they mature. Over time, sun-loving trees like the ponderosa pine will no longer be able to survive in these conditions. Instead, shade-loving trees such as white firs and Douglas firs will start to fill in the gaps in the forest, replacing grasses, shrubs, and any young ponderosa pines. As these trees crowd together, their dense branches and needles accumulate. Once the forest reaches this stage of succession, a lightning strike is more likely to cause a stand-replacing fire that would start the cycle all over again.

 

How Fast Does Succession Happen?

 
Fire impacts different ecosystems in different ways. Learn more about wildland fire in ponderosa pine forests, or explore fire ecology stories from around the National Park Service!
 
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Duration:
5 minutes, 50 seconds

Explore how the ponderosa pine is adapted to living in an environment shaped by fire.

 
  • Bright white lightning bolts strike down from dramatic dark clouds turning the night sky pink
    Fire History

    Learn more about the history of fire suppression and recent major fires in Bryce Canyon

  • A firefighter in a helmet, sunglasses and uniform uses a chainsaw to cut into the trunk of a tree
    Fire Management

    Learn more about the past, present and future of fire management strategies in Bryce Canyon

  • Flames against a black background.
    Fire Safety

    Learn more about fire safety.

Last updated: July 3, 2023

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