Month: August 2018

Lichens and Fires

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BC white fir_ LT- unknown sp 6.18
Hypogymnia sp. on conifer branch in British Columbia

Wildfire effects on lichens have recently been coming to the attention of biologists and foresters who are studying the long term effects of the very hot fires that have become more common in the North American west. The forests developed over thousands of years to withstand and benefit from low intensity, frequent fires. We humans suppressed the fires for over 100 years, and now the increasing but historically normal dry conditions and build up of unburned woody material in the forests, as well as the vast number of beetle-killed trees create conditions that encourage fires to start and burn hotter than normal.

Br Cr LT aspen trunk
Usnea sp, on aspen tree near Bragg Creek, Alberta

These super hot fires burn the forest more completely, killing all the lichens. Many years later there are no signs of lichens in the burned areas. Scientists suspect the lichens will not return until the forests grow large, older trees that provide habitat for lichens. The lack of lichens in a new forest will affect the health of the trees, and the ability of many animals and insects and birds to live in a burned over area. Many species depend on lichens for some aspect of their lives; without lichens, these residents disappear.

BR CR-LT aspen b
Aspen tree lichen community- Xanthoria, Usnea, Hypogmnia sp. (unsure of ID)

When we see the diversity and quantity of lichens in an established forest, it becomes clear they are an important part of the community. After a fire, and also after human logging activity forests do regrow, but we are only starting to understand some of the ways each member of the forest plays an essential role in making a resilient, vibrant, and sustainable environment that all life can depend on. We are starting to realize that some trees and other plants growing after a fire are only a small part of the life that needs to become established and begin cooperating to make a real forest. Maybe in the future we will change our management habits to not suppress natural processes, and when we do interfere, we will use more comprehensive methods to renew the forest, such as inoculate with lichen spores as we plant trees, consider helping other plants grow, and diversify the species we plant. We’ll also need to choose trees, forbes, lichens and maybe even soil microbes that fit the environment being addressed.

Invermere area LT 7-17
Hypogmnia sp. and Usnea sp. on conifer branch in SE British Columbia

We’ll need to think about the combinations and timing of introducing species. Just sticking some pine trees into the ground is not in any sense ‘reforestation’. (I planted trees for paper companies for years and was rudely awakened by what passed for ‘reforestation’.)

While we contemplate these ideas, we also have to learn at what stage of a forest’s growth each member of the community enters and establishes itself. We know in general, but I am sure we have a lot to learn. We know lichens are one of the first to colonize new earth, then moss, liverworts, ferns and on to larger plants. Each species, each facet of rock, wood or soil has special properties; they combine and change in minute but critical ways, in an elaborate dance with each other.

Toby Cr trail R-crustose 6.18c
British Columbia – lichen on rock

Maybe one of the good things to come out of the tragic fires in the western forests will be a desire to regrow forests that are resilient and adaptable as well as useful for our timber needs.

NOTE: Identification of lichens in these photos is tentative. If anyone reading this site has a suggestion for a more accurate identification, please contact me. Thanks!