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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 as applied ecology
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 results.
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. (taken from The Practice of Silviculture: Appled Forest Ecology, D.M. Smith, B.C. Larson, M.J. Kelty & P.M.S. Ashton, 1996).
ORIGINS
Almost all forest and woodland has been subject to man's activities at some time or other. In most parts of the world the dominant historical influence has been the clearance of forests for farmland. In Europe and the Middle East much of this clearance occurred in pre-Roman times. Up until the late Middle Ages the main use of woodland was in the provision of small and medium sized material for fuelwood, building poles, fencing and wattle. These products were mostly supplied by a variety of short rotation coppice systems. Demand for timber was satisfied by standard trees left to grow on amongst the coppice or form isolated trees in wood pastures where animals grazed the undergrowth or grass beneath. It was not until the early 1600's when wood scarcity and the decline in land productivity became an important resource issue across much of Europe. Modern silviculture was therefore born out of necessity to develop restoration techniques for sustaining the productivity of woodlands and forests. It is interesting to note that no matter what time period or where in the world forests are located, they are usually exploited first, and then after resource depletion silvicultural restoration is developed, and this is still going on throughout most of the world today.
Under the leadership of such men as Cotta, Hartig and Köenig, silviculture began to break away from its empirical basis and to find a foundation in the underlying sciences that were developing in the 18th and 19th centuries. Even before this time, Duhamel du Monceau in France and Enderlin in Germany had appreciated the need of lifting silviculture from the rule of empiricism. In 1767, Enderlin published a treatise on the characteristics of forest trees and of forest soils. Later, "Verhalten de Waldbäume gegen Licht und Schatten" by G. Heyer (1852) is probably the earliest attempt to analyze, in a comprehensive manner, a site factor operating in the forest. It is a classic, in which for the first time the theory of tolerance is described, upon which so much of our silvicultural practice is based.
Some of the most complex silvicultural techniques have been practiced for centuries in the tropics but on small scales. With the advent of colonialism "scientific silviculture" with the practice of rigorous experimentation and record keeping was first developed in Britsh India under the leadership of Brandis first director of the Indian Forest Service (1850-1885). His book "Forestry in British India" (1890) described silvicultural ideas that apear to have come full circle. He proposed silvicultural techniques for village and community forests, and the cultivation of a host of non-timber forest products.
In 1861, forest experiment stations were recommended by Elbermayer. It was not until 1866 that "oecology" (ecology) was first defined by Haeckel as the science treating of reciprocal relations of organisms and the external world. Methods of the silviculturists in the process of being worked out at forest experiment stations were seized upon by the plant ecologist. With the development of experimental plant ecology in the latter part of the 19th century, the work of the silviculturist and the work of the ecologist came together, both searching by means of experimentation for the fundamental laws underlying the relation of vegetation to the site. The field of the plant ecologist and the field to the silviculturist differ chiefly in magnitude and in the application of results. Although the student in silviculture has gained immeasurably from the ecological concept, the entire foundations of silviculture cannot be relegated to ecology. (mostly taken from Foundations of Silviculture, J.W. Toumey, 1928)
HISTORY OF SILVICULTURE AT YALE
In preparation
SILVICULTURAL ALUMNI/AE OF YALE
(Partial list of graduates of the Masters and Doctoral programs)
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