Forestry

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April 12, 2010, 6:06 pm
July 26, 2012, 11:49 am
Anjajavy dry deciduous forest, western Madagascar. Source: C.Michael Hogan

Forestry is the science and practice of managing a forest. Prior to the establishment of forestry as a science-based discipline, the exploitation of forests for various products was sometimes carried out without sufficient regard for consequences. For example, trees were cut without always ensuring tree regeneration. Logged areas were sometimes burned without regard for soil resources, and logs dragged or flushed down stream valleys to a mill without concern for the stream habitat or water quality.

Scientific forestry is intended to alleviate these unintended consequences by basing management on research and a goal of sustainable forest regeneration. The practice of forestry encompasses forest protection, wildfire prevention, forest engineering, silviculture, forest ecology, economics, biometrics, hydrology, wildlife management, and other disciplines.

Forest Threats

Time history of wildfire acreage burnt in USA since 1900, showing significant decline since 1928. Source: US Forest Service.
Forests face multiple threats, such as fire, disease, invasive species, insect outbreak, and air pollution damage. With regard to air pollutants, the chief culprits are sulfur dioxide, oxides of nitrogen and heavy metals. The largest present sources of these airborne pollutants are unscrubbed power plants and other industrial sources in China, India and Brazil.

Some factors may create chronic stresses which may have long-term consequences on the nature of a forest ecosystem and the species within. Forest management activities are, therefore, undertaken to reduce fire risk, control pests, and to guide forest development processes towards specific, often multiple-use, management goals. Techniques include vegetative thinning and controlled burns to reduce fire risk, application of pesticides to control insect outbreaks, and removal of diseased trees.

Some of the greatest threats derive from poor forest management of wildfire risk. California, for example, has engaged in many well-meaning practices that have resulted in very high forest fire risk: (1) aggressive fire suppression; (2) overzealous reduction of timber harvesting; (3) failure to reduce forest fuel, especially dead wood and extensive chaparral; (4) allowing homeless encampments and marijuana farms in forested areas. In contrast, the original inhabitants of Ohlone and other Native American tribes had disciplined programs of controlled burns and forest clearing to mitigate fire risk.

Forest ecology is the study of the forest as an ecological system. Facets of this science include tree physiology and life history, wildlife biology, nutrient cycling, biogeography, and other factors. The results of studies in forest ecology help inform silviculture as well as efforts to document and conserve biodiversity.

Forest hydrology is concerned with the effects of forestry operations on hydrologic properties of rivers, streams and watersheds, water yield, water quality, and stream biota. Specific interests are preventing soil erosion and encouraging optimum stream flow and water temperature for aquatic biota.

Forest Management Technology

Biometrics and forest mensuration are concerned with sampling and measuring properties such as stem form and biomass, site index, stand wood yield, and other parameters. These fields are called upon also for the design of forest inventories and analysis of inventory data.

Forest management is typically extensive rather than intensive. The basic spatial unit of management is the forest stand, which is a somewhat homogenous and identifiable spatial unit. When a prescription like thinning or fertilization is applied, it is applied to one or more stands as whole units. This is because operational efficiencies can only be achieved in this manner and because detailed spatial manipulations (e.g., fertilizing at different levels for each tree) are not feasible with the information and techniques available. While certain scales of complexity of spatial pattern can be achieved, such as by selection or strip cutting or leaving remnant trees or patches, not all possible configurations are feasible. In addition, there may not be any known prescription that would favor a particular species (such as an endangered species) or remove a pest or alien species.

Modern forestry often utilizes large equipment, and thus a cadre of engineers. Unique achievements of forest engineers include cable yarding systems, the design of forest roads that produce less sediment, and the development of field harvesting equipment that increases efficiency.

Silvaculture

Silviculture is the art and science of growing trees. Various silvicultural systems have been devised to harvest a stand (or selected trees) at lowest cost and with minimal damage, to ensure restocking of the site, to help trees grow rapidly, or to favor particular species. A common mistake in early silvaculture was to promote a monoculture. Not only does this discourage biodiversity, but can often increase wildfire risk.

Commercial Forestry

Commercial forestry is necessarily carried out based on an expectation of profit. Non-market benefits (e.g., biodiversity goals, aesthetics) can and need to be accommodated to maintain a social license to manage the forest, but they must not be too demanding of corporate resources (e.g., staff time, land area) or competing land-uses will be selected. Forests on public lands, and particular those located in designated wilderness areas, are sometimes managed for non-commercial goals, including wildlife habitat restoration, old-growth preservation, water resource protection, preservation of biodiversity, and rare or endangered species conservation. Management strategies for preservation-related purposes may not generate net income from the harvesting of forest resources although other local and regional economic benefits may be derived from recreation related activities, and by other environmental services provided by forests such as water quality and air quality protection.

Since forestry is often conducted as a business, the economic aspect of forestry has long received attention. Forest economics encompasses field operations (such as timber harvesting), long-term stand management strategies, forest-wide economic planning, assessments of the impact of forest policy on nearby communities, and even international market assessments of wood supply and effects of tariffs and tax policies.

Forests of the World

There are a diverse set of forests across the globe, including variations with latitude and altitude as well as varied soil types and hydrology regimes; an important delineation is between broadleaf and conifer dominant forests. The following is a cross section of forests around the Earth:

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Citation

Craig Loehle, C. Michael Hogan (2012). Forestry. ed. Stephen Nodvin. Encyclopedia of Earth. National Council for Science and Environment. Washington DC. Retrieved from http://editors.eol.org/eoearth/wiki/Forestry_(Wildlife)
Content Cover ImageImage Source: Montana State University.