Silviculture: Applied Forest Ecology

Silviculture has been variously defined as the art and science of producing and tending a forest; the application of knowledge of silvics in the treatment of a forest; or the theory and practice of controlling forest establishment, composition, and growth. Since silvicultural practice is applied forest ecology, it is the biological technology for forests and woodlands that carries ecosystem management into action. Like the rest of forestry itself, silviculture is an applied science that rests on the more fundamental natural and social sciences. The immediate foundation of silviculture is silvics, which deals with the growth and development of trees and other forest biota as well as of the whole forest ecosystem.

Silviculture is designed to create and maintain the kind of forest that will best fulfill the objectives of the owner and the governing society. The production of wood (timbers, fiber, fuelwood), though the most common objective, is neither the only nor necessarily the dominant one. It is a mistake for foresters to assume that timber production is or should be the sole objective of silviculture. Frequently, especially with public forests, such benefits as water, wildlife, grazing, recreation, or aesthetics may be important; water and wildlife always have to be taken into account. Silviculture is the oldest conscious application of the science of ecology and is a field recognized before the term ecology was coined. Many ways of governing the development of forest stands rest heavily on cuttings and other treatments that alter or modify the factors of the stand environment that regulate the growth of the vegetation.

The reliance on ecological knowledge is all the firmer for resting on the virtues of the necessity and not simply on philosophical principle. The economic returns from forestry are not high enough to make it feasible to shield forests from all the vicissitudes of nature. Therefore, silviculture is usually far more the imitation of the natural processes of forest growth and development than a substitution for them. These processes may be improved upon, channeled, and limited; however, excessive disruption leads to severe losses, high costs, and other unfortunate consequences, immediate or delayed.

The necessity that nature should be understood and emulated does not mean that silviculture should slavishly follow either the reality of natural processes or abstract theories about them. Most forests live longer than people. It is, therefore, not easy to recognize that the natural disturbances that renew forests, often after intervals of centuries, are usually catastrophes such as fires, windstorms, and insect outbreaks. There are also forests that are slowly and continuously renewed by minor disturbances, but these are far from being any universal or typical form of nature.

Paramount among the objectives of forestry in general and of silviculture in particular is the maintenance of the productivity of the living forest. The site is the total combination of factors, living and inanimate, of a place that determines this productivity. The site factors that are most subject to long-lasting harm are those of the soil, which is the most nearly nonrenewable of the resources in silviculture. The basic supply of solar energy, the most vital site factor, is beyond silvicultural control. Silviculture rests heavily on manipulation of the microclimate of a site, but its effects on the macroclimate are limited to those caused by photosynthetic removal of carbon dioxide from the atmosphere. Forests are the result rather than the cause of geographical precipitation patterns.

Silviculture is not conducted in a pure state of nature, and this state ceased to be pure when society advanced beyond the food-gathering stage. To the extent that civilization is partly artificial, it can be argued that forestry must also be partly artificial in ways calculated to keep the world ecosystem in healthy dynamic equilibrium. However, the farther that any artificially induced process departs from nature, the more perilous it is if only because it becomes harder to predict the result. The web of life is so intricate that it is easy to argue that one should do nothing to the forest for fear of doing something wrong. This is the indictment pure science continually brings against the technology of applied science. The charge can never be entirely refuted, but society requires practitioners of applied science to act in the absence of full knowledge. The best that they can do is to proceed by adaptive management in which one takes action based on the most complete knowledge available. The results are monitored, and the management practices are changed or otherwise adapted as one learns from the results.