FOREST PROTECTION

Animals

The forest is home to many animals that use it for shelter and food. Trees are food sources for various animals whose impact on the forest are generally insignificant. Significant damage may occur in forests that are managed for timber production when the trees suffer damage that reduces their growth potential or causes physical defects.

Animals that feed on trees fall into three categories: stem eaters, browsers, and seed eaters.

Stem eaters such as beaver, bear and porcupine feed on the nutritious cambium layer found between the bark and the wood. Those areas where the cambium is removed die causing the tree to lose vigor as it expends energy sealing the wound with pitch. If enough cambium is destroyed, the tree will die. Tree wounds provide an entry site for insects and disease. Porcupines eat cambium near the treetop, often killing the upper portion of the tree. Bears may also be attracted to cambium in the spring when the cambium is richest in sugars. A bear can feed on several trees daily, eating the cambium at the base of the tree and killing trees up to 20 inches in diameter. Foresters have recently created feeding stations in areas where bear damage has occurred. The bear can feed itself with sugary pellets until other natural food plants become available.

Browsers such as deer, mountain beaver and rabbits eat the branches and leaves of young trees. They may kill the tree or deform it by altering it growth pattern. Most importantly in Western Washington these animals often reduce a small tree's height. Seedling height is critical in overcoming competition from brush species, which may grow faster than conifer seedlings. When the brush becomes thick and taller than the seedlings, the seedlings begin to die from lack of light and nutrients.

Seed eaters such as squirrels and chipmunks reduce the amount of seed available to forest nurseries or for natural seeding. However, it is also believed that squirrels may actually inoculate seeds with a beneficial fungus. Inoculated seed may have a competitive edge over other seed.

Birds are important to the forest in two ways. First, some birds such as woodpeckers eat insects that are harmful to trees. Second, birds spread tree seeds in their droppings.