Breeding the Coastal Giants
By Awake! correspondent in Canada
A WALK in a towering grove of trees is surely one of the most impressive, even awesome, experiences one can have. Seeing the streams of light and colors, breathing the cool, fresh air, and feeling the stillness and peace is indeed inspiring.
North America’s Pacific Northwest is well-known for its vast woodlands. The mountains, valleys, and fjords are covered with prolific growths of the famous coastal giants—cone-bearing softwood trees. Hemlock, balsam, pine, cedar, spruce, and fir all grow tall here. The renowned Douglas fir can reach nearly 300 feet [90 m] in height!
There is much more to these trees than their magnificence, however. They are of importance to the livelihood of loggers, truckers, road builders, mill hands, towboat operators, and others. And from the trees are produced the raw material for thousands of manufactured goods to satisfy consumers. So important are trees that scientists and forest managers are endeavoring to find ways to speed up their growth and to improve the yield of the forest. To do this, they have turned to the science and art of tree breeding.
Why Tree Breeding?
Trees in a forest, like faces in a crowd, are distinctive. Each one is a little different from another in height, foliage, and limbs. And it may also differ in ways that you cannot see.
Some trees grow faster than others. Some yield wood of greater strength, density, and clarity (freedom from knots) than others. And some have greater resistance to pests and diseases. All these things matter greatly to the forest industry.
Forest managers naturally want trees that grow fast, resist disease, and yield high-quality wood. And for ease in logging, transporting, and milling, trees of fairly even size are most desirable. But trees that fill the bill—the old growth that stood here when the first loggers arrived in the mid-19th century—have already been harvested. The trees that are cut today, second-growth trees, are smaller, grow more slowly, contain less wood, and are of uneven quality. It is the tree breeder’s job to produce trees that possess the desirable characteristics. This has led to the tree-improvement programs now operating in the Pacific Northwest.
How It Is Done
Tree breeding begins with selection. In the area where reforestation is planned, a team of technicians goes cruising among stands of trees in search of plus trees—trees that appear to offer the greatest genetic potential for breeding.
If stand cruising sounds like a pleasant drive through the woods, it is at best half true. It is a painstaking search. Each prospective plus tree must match a checklist of characteristics—good cone production, fast growth, straight stem, absence of disease, and so forth. But in this job, appearances can be misleading. That splendid, healthy, 130-foot [40 m] fir may be taller, but did it grow faster or is it simply older? Does it happen to have better exposure or drainage, or is its size really due to superior hereditary endowment?
Once a satisfactory specimen is found, it is tagged and numbered. But, now, how can it be bred to produce other superior trees? Nothing would be gained by uprooting and replanting it elsewhere. Nor would it be of benefit just to take its seeds and plant them. This is because there is no way of knowing which one of the surrounding trees pollinated the seeds, thus making them genetically impure. What is needed is a cutting from the tree. Yet how can it be obtained?
The lowest branch is high above the ground. So a sharpshooter raises his rifle and fires. Down glides the tip of a healthy branch. This cutting, called a scion, is then taken and grafted on to the rootstock of a young tree in a seed orchard. There the grafted scion will grow into a genetic duplicate of the parent tree—a clone.
The site of the seed orchard is carefully chosen so that the grafted clones will not be pollinated by trees in the wild. When the clones mature, the reproductive flowers, protected from airborne pollen by paper envelopes, are pollinated artificially with a hypodermic needle. From the resulting seeds will come a new generation of seedlings, or young plants. For every step along the process, and for each seedling, detailed information must be kept so that the origin of the plus tree, the source of the pollen, and a host of other information can be traced.
The seedlings are then taken to a site near the plus tree and planted to see how they perform. Like human offspring the trees may reflect favorably or unfavorably on their parents. If they do well, their scions may form the basis for a second-generation seed orchard. The seeds from these scions may be sold commercially for up to $260 (U.S.) per pound [58 cents per gram]. But if they do poorly, their parents, the clones, may be uprooted from the orchard, and the plus trees from which they derive will be stricken from the program. New plus trees must be found, and the painstaking process starts all over again.
All of this takes a great deal of time. A breeder of trees may not expect to see even one full-grown generation resulting from his work. It takes up to ten years for a seed orchard to produce seeds in usable quantities. It takes another ten years to test the offspring of the orchard’s trees. Finally, it takes another 50 to 60 years for the trees to reach harvestable size.
There Are Dangers
As noted before, if the grafted scions do poorly, years of work can be lost. Thus, the temptation is great to stick to only a tiny number of the finest and proved plus trees. But there are hazards in doing this. What are they?
Each tree, like each person (with the exception of identical twins or triplets), is genetically unique—a genotype. The fewer the genotypes in a tree-breeder’s gene pool, the fewer the different genes in that pool, and the greater the hazard that some disease or pest will wipe out a whole generation of trees, even an entire forest.
Therefore it is wise to have a bigger gene pool, even though some of the plus trees used are not as fast-growing or as straight. Using a number of plus trees reduces the risk of wholesale destruction.
Future of Tree Breeding
Though it may be another 50 years before results from tree breeding done today will be forthcoming, the bonus is that forests planted with improved seeds will be marketable in 10 to 20 percent less time than those planted with ordinary seeds. And some experts are predicting that tree breeding could increase the volume of harvested timber by up to 25 percent on a given piece of land. This benefit, along with better resistance to disease and pests, stronger and cleaner wood, and better seed production, makes tree breeding a vital part of forest management in the Pacific Northwest.
Time remains the tree breeder’s enemy. It takes too long to see results, to make decisions, to press on with the next step. Trees, and especially the conifers, have always outlived us. But the Bible points forward to the time when that will no longer be so. “Like the days of a tree will the days of my people be,” it promises. In fact, God promises that his people will live forever. (Isaiah 65:22; Revelation 21:3, 4) Then humans will have time to explore the fascinating genetic potential that still lies hidden in plants and animals.
[Pictures on page 26]
Shooting down a cutting from a tree