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Problems Related to the Loss of Dead Wood


Snags (standing dead trees) and rotting logs are essential to a healthy forest in several ways:

The importance of snags in a healthy forest

When trees die they usually remain standing for ten years or more. These standing dead trees are called snags. Snags provide a place for woodpeckers to make holes for nests. Woodpeckers eat insects which kill trees. The biggest woodpeckers, that eat the most insects, need the largest dead trees. When the woodpeckers abandon their holes in the dead trees they become nest holes for other birds which eat the insects that kill trees.

Scientists are finding that insect eating birds form a sort of roving hit team. These birds move from burned area to burned area in their search for insects to eat. If there are enough burned and insect defoliated areas that are not salvage logged, then populations of these birds will be maintained at a level that is sufficient to provide a quick response to insect epidemics. Since birds are highly mobile they can protect a very large area if their numbers are sufficient to control localized outbreaks.

Scientists claim that the biggest snags are the best habitat for woodpeckers and insect eating birds. Still, in a pinch, snags as small as 15 inches in diameter will provide some of the benefits of larger snags, if they are on a site without larger snags.

The importance of down logs in a healthy forest

After ten or twenty years these snags fall to the ground where they become home to ants and other creatures. Carpenter ants eat lots of the insects that kill trees, as well. Pileated woodpeckers eat lots of carpenter ants during the winter, when other bugs are hard to find. Carpenter ants require large rotting logs which must be present in sufficiently great amounts that enough of them will survive the frequent fires that burn the undergrowth in a healthy Ponderosa Pine forest. If there is adequate carpenter ant habitat, their populations can increase rapidly in response to increases in their prey. The limiting factor is large down logs. While ants don't move around as fast as birds they are quite effective in controlling infestations of tree killing insects.

Down logs also provide habitat for small rodents. These creatures are important to the health of the forest because they spread the spores certain kinds of fungi in their dung. These fungi are important because they help the roots of trees to gather water and nutrients. These fungi have fibers that interconnect acres of forest. The mushrooms that we eat are the fruit of these fungi. Small rodents also eat these mushrooms. These small rodents hide from predators under the round parts of down logs. They use the security of the round space in the shadow of a large down log as a path into the burned opening. Sometimes after a fire, the only way the fungi can get back in touch with the roots that need them, is if the spores are carried into the fire area by small rodents.

The importance of underground wood in a healthy forest

As the ants and other creatures eat holes in the down logs they gradually rot into the forest floor. Bacteria, which eat this rotting wood, make nitrogen and other nutrients available to feed the trees that are growing in the forest. These rotten logs also soak up water like a sponge. In the dry inland western forests, rotting underground wood supplies most of the nitrogen and most of the late season water storage.

The importance of large green trees to replace dead wood

In order for there to be enough big snags and down logs to maintain the health of the forest, there must be a lot of large, live, green trees to replace them when they fall and rot. These large live trees are like the spark plugs in your automobile engine. While it appears at first glance that there are plenty of spark plugs and you can take some of them out without missing them, you soon find that the engine doesn't run as well without the plugs. If you take too many of them out the engine won't run at all.

Land management agencies want to salvage log

The Forest Service and BLM like to salvage-log trees that have been killed by insects or fire. Many salvage sales log the remaining big trees that were killed by insects and fires. In some ways, fire salvage is even worse than insect salvage. Fire salvage takes the big trees, that should be left to protect the forest from insects and disease, out of the forest. These big dead trees provide the only shade and wind breaks for young trees growing in these areas.

These dead trees are doubly important since they are the only source left on burned sites for the rotting wood which is so important to feed the soil for future forests. Some burned snags will stay standing almost twice as long as snags that are not burned. In the absence of green snag replacement trees, these large burned snags can provide shade and habitat in a burned area until young trees have matured.

We know of burned areas that were logged after fires several years ago. These areas are next to burned areas which were not logged. When we looked at the logged areas the young trees were barely holding on and it felt hot and dry. The unlogged areas were cool and moist and the young trees were doing well.

If too many big dead trees are salvage logged, there will not be enough left to provide homes for the birds and ants to eat the bugs that kill trees and you will get insect infestations. Underground wood comes from large trees which died and fell to the ground without being salvaged. If all the dead wood is salvaged to keep it from "rotting on the forest floor", then there will be no food for the bacteria and fungi which feed the future forest.

Proper salvage sales must not take any big trees because there are not enough of them to protect the forest. Most of the biggest trees were logged long ago. Proper salvage sales would have to lose money because it costs more money to log small trees than it does to log large trees. The only way that most of these sales can be sold is if the agencies "sweeten the pot" by adding big trees to them. This results in a vicious cycle where the habitat for the insect eating birds is destroyed by the sale which was proposed to get rid of the insect killed trees.
 

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