8 Improving the Forest

Over many years nature improves forests by removing inferior trees, an example of natural selection through the survival of the fittest. But many natural events and human activities affect this process. Fires, floods, wind and ice storms, and harvesting practices all affect the growth of the forest. In general it is fair to say that nature’s events generally improve the forests over the years and the activities of human beings in the past have harmed them.

Recently, through forest management, human beings have begun to do less harm, perhaps even help forests. In controlling the composition of the stand by planting species they prefer, human beings can improve the quality of the trees they plant. Much has been learned about the develop­ment of genetically improved strains of corn, wheat, and other food crops. This improvement can be accomplished quickly because these crops pro­duce a new generation each year. Progress is slower with trees because they often take many years to produce seed.

When forest managers think of improving trees, they want trees with long, straight trunks that can be sawed into lumber or peeled for plywood more economically. They want trees with small crowns, or tops, so more trees can get sunlight and grow on each acre. They want trees that are in­sect and disease resistant so their chances of maturing are better. And they want trees that will grow to commercial size as rapidly as possible.

Forest scientists have accomplished all these goals with pines and with some hardwood species such as sycamore, cottonwood, and yellow poplar. They have even learned to clone a superior tree, a process that pro­duces more trees exactly like it. This is done in the laboratory by forcing tiny cuttings from the tree to develop roots and leaves.

The most commonly used method of tree improvement involves first locating superior specimens of the species. Branches are collected from their crowns, often by shooting them off with guns.

The branches are grafted, or joined, onto rootstocks in special nurseries where they grow until they are old enough to bear seed. A great advantage of this method is that tree branches that come from mature trees bear seed much sooner than do trees that are grown from seed. The flowers on the selected branches are carefully pollinated with pollen from other superior trees. Thousands of combinations of pollen trees and branch trees are tested. The resulting seed is then planted. Many of the trees that grow from the seed have all the bad characteristics of their parents. But some have all the good characteristics. Forest scientists try to produce and plant as many seeds having the good combinations as they can.

An example of what can be achieved is that improved species of pines produce much more usable wood in the same time as ordinary wild trees produce relatively little. Such improvements mean that more wood can be grown on less land in a shorter time. As the world population grows and requires more land for home sites and food production, this ability to maximize wood production on each acre will be vital to future generations.