Plant Adaptations to Fire

To-Do Date: May 3 at 9:30am

Plants that are adapted to fire are called fire-adapted species.  In contrast, some plants do not tolerate fire, and these are called fire-sensitive species.  On this page, you will learn about some strategies used by fire-adapted plant species. 

Plants that are adapted to fire have advantages in the post fire habitat. All of the competition has been burned away. The soil is newly enriched with the minerals from burnt vegetation. And finally, many some species produce chemicals that inhibit other plants from growing (a kind of chemical warfare  plant style). Those chemicals get burnt away in fires. 

 

Study Guide

 

2. Fire is a natural part of California's ecosystems. What are plant adaptations to fire?

• • What adaptations do they have to surviving fire?
  • What adaptations do plants have to reproducing after fire?
  • What are the advantages for a fire adapted plant after a fire? 
  • What is the role of natural selection in determining plant adaptations?

Fire Adaptations: Thick Bark

The outer bark of a tree is non-living tissue that protects living tissue within.  Thick bark can insulate the tissues beneath when there is a fire, minimizing damage caused to these tissues by increase temperatures.  In contrast, fire-sensitive trees have relatively thin outer bark that burns through quickly, allowing damage to the living tissues underneath.

Many local trees have thick bark that allow them to survive fires.  Below are some pictures of species with this adapatation and the ecosystems in which they are found.

 

Fire Adaptations: Resprouting

Many fire-adapted trees and shrubs are able to grow new shoots after fire. These plants resprout from buds belowground that are protected from fire damage.  Below are some picture of local species that can resprout, and the ecosystems in which they occur.

 

Fire Adaptations:  Serotinous Cones

Some conifers have cones that say closed on a tree after the seeds inside mature, because the cones are sealed with resin.  These cones are called serotinous.  Serotinous cones can remain on a tree for decades until the heat of a fire melts the resin, opening the cone and releasing the seeds.  The adult trees are often killed, but the seeds released from the parent generation will germinate and grow together as a new cohort of trees.  

Watch the short video below of a cone opening in a toaster oven.

We have local conifers that produce serotinous cones, and they often occur in a unique forest type called "closed cone forests."

 

Fire Adaptations: Seed Germination Triggered By Fire

The seeds of some plants can remain dormant in the soil for long periods of time until they receive an environmental cue to germinate.  For some plants, fire is this cue.  In some species, the heat of a fire can damage the tough seed coat, allowing germationa to occur.  In other species, chemicals in smoke can trigger germination.  

Seed germination as a fire adaptation can occur in trees or shrubs that exhibit some of the adaptations discussed above.  For example, a shrub called chamise, found in chaparral, can survive and resprout, but also has seeds that germinate after a fire.  Other shrubs, like some manzanitas and California lilacs (in the genus Ceanothus)  also found in chaparral are killed by fire, but their seeds will germinate, reviving the population.  

Some annual plants are triggered to germinate after a fire.  The seeds will remain dormant in the soil until the fires triggers germination.  They will then grow, often in large numbers, for only the first spring following the fire.  Once they flower and produce seed, the adults die, and they population will hide out of site in the soil until the next fire.  These annual plants are often referred to as "fire followers" because they are ony seen following a fire.

A common fire follower seen in Sonoma County after the 2017 fires is Whispering Bells, shown below.

 

Watch the short video below about fire followers in montane forests.