Redwood Forest Ecology

Redwood forests are complex ecosystems. From the tallest trees in the world to the tiniest fungi, the whole forest is a working system in a very delicate balance. Everything has a role to play in this forest.

The redwoods themselves influence the climate of the river canyons by transpiring moisture which keeps the humidity high. Evening fog from the ocean rolls into the canyons and condenses on the tree leaves. This condensed fog falls to the ground as raindrops. The trees are able to use this moisture. A single tree can release up to 500 gallons of moisture into the air per day. The region also receives large amounts of rainfall. The trees grow well here because they receive plenty of water.

In turn, the trees support wildlife. Birds build nests in the branches and small mammals, such as red tree voles, bats, flying squirrels, chipmunks and squirrels, also find shelter in the trees.

When the trees lose their leaves, decomposers such as banana slugs, redwood snails and numerous kinds of fungi, begin to break down the leaves into nutrients which will be leached back into the soil by the rain. These nutrients can then be used by other trees and plants.

When a tree finally succumbs to age or a windstorm and falls to the ground, it begins a new life as a log. The downed log serves as homes for many animals. Many plants will take root and grow on these logs. As the logs rot, they become spongy and are able to store lots of water. Other plants will send out roots to use this resource. Insects deposit their eggs under the bark and the larvae tunnel their way out after they've hatched. Because other plants are able to take root on these logs and survive off the stored nutrients, they are called nurse logs.

As a log rots, it releases nutrients to the soil and to other plants. It can take 500 years for one of these huge logs to rot away. During that time, many animals will use it for shelter. Fungi will attack the log and work to break it down.

The standing dead trees, or snags, serve as places for birds to nest. Ospreys along the river build their nests on the tops of these spiketop trees where they will have a view of the river. Spotted owls use snags as nest sites as well.

Another endangered species, the marbled murrelet, depends on old-growth forests. Instead of building nests, they make a hollow in moss and other debris which has accumulated on a high branch.

When these trees are alive and healthy, they are remarkably resistant to the forces that tend to kill other trees. Insects do not attack live redwoods because the wood contains tannic acid, which is bitter. The bark can be up to a foot thick, which provides the tree with excellent insulation from fires. Floods, which deposit soil around the base of the trees, do not smother the roots. Other trees would die when their roots are thus smothered. But, redwoods can grow new roots up into the newly deposited soil. The main cause of death for these trees is windthrow. The soil becomes saturated from rain and high winds can knock over the giant trees.

Fire plays a role in redwood forests as well. Low-intensity fires clear away undergrowth and material that has accumulated on the ground. This opens clear areas on the forest floor and allows seeds to germinate on clear soil. The ash from the burned material provides nutrients for the soil.

Periodic fires burn off the downed limbs and small trees. If these are not burned off, the material will accumulate to a dangerous level and create a fuel ladder which may allow a fire to spread to the crowns of the trees.

Fires in the open prairies keep them open and free ov vegetation. Fires also encourage the growth of tanoaks and berries. For this reason, the Native Americans of this area periodically burned the prairies to encourage the growth of the plants they used for food.

These forests are more complex than they seem at first glance.

Additional redwood ecology links:

[The Rockefeller Forest]
[Natural History of the Coast Redwood Forest]

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Revised: 8 October 1996
Copyright © 1996 Humboldt Redwoods Interpretive Association