Dead trees are good homes

When many of us think of a healthy forest, we think of tall, green trees. It’s hard to imagine how a tree killed by mountain pine beetle could be good for a forest. However, to be truly healthy and support all the wildlife that depends on it, there must be a variety of young, old and dead trees in a forest ecosystem. At “endemic” or normal levels, mountain pine beetles help maintain this diversity by colonizing and killing old or damaged trees, therefore kick-starting the invaluable process of decomposition. Decomposing wood returns nutrients to the system while providing shelter and food for many plants and animals. Standing dead trees host a diversity of organisms that would not be present without them.

Woodpecker Holes © Parks Canada

In the study of food chains, trees are known as “producers”. This means they create their own food from sunlight through a process called photosynthesis. A healthy forest has producers, but also “consumers” (that hunt or forage for nutrients to survive) and “decomposers” (that obtain nutrients by breaking down parts of organisms into simple forms). The relationship between producers, consumers and decomposers is often depicted as a “food web”. A healthy forest has many food webs, including important webs created by dead trees.

Food Web © Parks Canada

Carpenter Ants and Weevils:
Once a tree dies from mountain pine beetle colonization, other insects like carpenter ants and weevils move in to eat the wood.

Pileated Woodpecker:
Birds like woodpeckers feed on ants and other insects. Pileated woodpeckers also seek dead trees to chisel out cavities that they live in seasonally for several years. These cavities provide protection from predation by hawks and shelter from the weather. Pileated woodpeckers can carve out roosting cavities that measure 15 centimetres in diameter and 48 centimetres in depth. No other bird can carve such large holes in a tree.

Pileated Woodpecker © Parks Canada

Cavity Dwellers:
When woodpeckers abandon their cavities, other animals use them. Tree cavities created by Pileated woodpeckers are important to 50 species of tree cavity dwellers that are unable to create their own. Some of these animals are flying squirrels, red squirrels, weasels, martens, bats, pygmy owls, saw-whet owls, boreal owls, and tree nesting ducks such as buffleheads and goldeneyes.

Boreal Owl © Parks Canada

Flying Squirrel:
The flying squirrel is an animal that uses old woodpecker cavities for new homes. One of the favourite foods of this squirrel is mushrooms. As a result, their scat is full of fungi and the associated bacteria. By eating mushrooms, squirrels help spread this fungi around.

Flying Squirrel © Parks Canada

Fungi:
A type of fungi spread around by squirrels is called micorrhiza. These fungi are important to living pine trees, because they help the roots take nutrients into the tree. The fungi benefits from this relationship by getting nourishment from the tree in return.

Mushrooms are a type of Fungi. © Parks Canada