One of the biggest boons to future forest growth may come from one of the past's chief villains: fungus. In prospect: faster-growing trees to revivify strip mined areas in the US; and replenishment of denuded forests in the Third World.
Thousands of fungi that are destructive to plants and trees carpet the forest floor and thrive in furrowed agricultural fields. But others, such as mycorrhizae, actually help vegetation grow, particularly in poor soils.
Researchers are now closing in on using certain strains of mycorrhizae to boost tree growth, which could have a big impact on forestry practices around the world.
Mycorrhizae are widely found in most soils. Many plants and almost all trees need them to survive. The fungi cling to their tiny feeder roots and help them suck up water and nutrients from the soil.
Researchers with the US Department of Agriculture report that in normal soil pine trees inoculated with mycorrhizae grow up to 20 percent faster than untreated seedlings. Between 5 to 20 percent more of the treated trees survive.
But the effects are even more dramatic in ''hostile'' soil areas, making the fungi of potential use in sprouting forests on wastelands. Several million acres of coal spoils, slag dumps, gravel pits, and strip-mined areas dot the US. Here the soil is often too acidic or chemically tainted to support anything but hardy grasses.
In USDA field tests, inoculated pine trees planted in strip-mined areas of Appalachia have grown as much as four times faster than normal seedlings. ''The poorer the soil conditions, the better it works,'' says Dr. Donald Marx, a scientist with the USDA's forestry experiment station in Athens, Ga.
The fungi may boost reforestation efforts in third-world countries as well. Mycorrhizae are being tested in parts of Asia, Africa, and Latin America, where wood remains a chief source of fuel but forests are being rapidly denuded. The hope is that fungi-treated seedlings will not only speed replanting efforts, but will also help pine plantations flourish in savannas and other vegetation-shy stretches.
Timber companies are interested in the fungi to reduce the tree mortality rate. On average, about 20 percent of the 2 billion seedlings planted in the United States each year don't survive. In dry years, the rate can top 50 percent.
Mycorrhizae are not expected to be commercially produced for another one to two years. The chief snag remains in discovering how to produce the fungi quickly enough and in large enough quantities to be economical. Unlike some fungi, such as common bread mold, mycorrhizae don't reproduce in a few hours. They take several weeks.
Moreover, the organisms must be kept alive long enough to be transported where they are needed.
Dr. John Litchfield, a Battelle Laboratories researcher, predicts large-scale commercial use is five years off.
Just as promising, but further off, is the use of a different mycorrhizal species to improve the growth of a wider range of trees and some food crops. These fungi (called endomycorrhizal, vs. the ectomycorrhizal used in the pine-tree research) are being tested on some hardwoods as well as peaches, apples, citrus, soybeans, and tomatoes.