Globally, forests play a large part in ecosystem functions, biodiversity and economics.It is estimated that there are somewhere between 5 and 30 million species on Earth. Forests provide habitat for some two thirds of these.Approximately one half of the world's forest carbon is found in boreal forests and over one third in tropical forests.According to 1994 estimates, forests provide approximately US$969 per hectare per year (a total of US$4.7 trillion per year) in goods and services annually. These functions include nutrient cycling, climate regulation, and raw materials.Some 60 million people (indigenous and non-indigenous) inhabit forests and depend on them for their livelihoods.In the early 1990s, the production and manufacturing of industrial wood products contributed US$400 billion to the global economy, approximately 2 percent of the global GDP.
Source: http://nwpwa.allegheny.edu/forestfacts.htm

Harvesting Techniques

Single-Tree Selection
By: Thomas C. Croker, USDA Forest Service, www.forestryimages.org
The single-tree selection method removes individually selected trees throughout all diameter classes, creating small gaps in the canopy to facilitate regeneration. This method is generally the most expensive method of harvesting and requires the greatest amount of care and skill on the part of the forester and logger. Advanced regeneration established before the harvest must be of shade-tolerant species that are known to grow well in the low-light conditions that persist even after harvest.

Group Selection
The group selection method removes trees in a number of 0.1 to 1-acre areas to create openings in the forest canopy. The larger the opening, the more likely that regeneration of sun-loving (shade-intolerant) species will develop and persist in the openings. Shade-tolerant species are more likely to sprout and survive near the edges of the opening and in the uncut forest between the openings. For shade-tolerant species to compete successfully, with shade-intolerant species in the openings, they should be present as advanced regeneration before the harvest.

Shelterwood Method
The shelterwood method leaves a large number of trees standing long enough to establish and protect "advanced regeneration" sites until the seedlings and saplings are well established. (Because the residual trees also serve as a continuing seed source, the shelterwood method is desirable when insufficient advanced regeneration is present.) After regeneration is well established, the sheltering trees are harvested, permitting the advanced regeneration to occupy the site fully.

Seed Tree Method
By: Robert F. Wittwer, Oklahoma State University, www.forestryimages.org
The seed tree method leaves a few of the best trees standing to become the parent trees of the new forest. This method has limited application in Pennsylvania forests.

Clear-Cut Method
The clear-cut method, in its pure form, removes all of the trees in a multi-acre area in a single cut. However, as management plans have evolved to include multiple objectives, it is not unusual to find that even in a clear-cut area, some tree species are reserved in the interests of biodiversity, wildlife habitat, or aesthetics. These include rare or slow-growing species, good mast producers, and wolf trees, den trees, and some snags. This method is the most controversial harvesting method and is often the target of public outcry. However, there are biologically based justifications for clear-cutting, given that the requirements for regeneration have been satisfied. Clear-cutting may be the best way to promote early success ional forests that are essential for numerous plant and wildlife species. Clear-cutting is the best method for regenerating those tree species (such as black cherry, aspen, and yellow poplar) that require full sunlight, at least in their early life.

High-Grading
High grading is the harvest of only those trees that will give the highest immediate economic return. There is concern among all sectors of the forestry community that high-grading may lead to a widespread decline in forest resource quality. Two practices, diameter-limit cutting and selecting cutting, generally fall into this category. In diameter-limit cutting, all sellable trees above a certain diameter are harvested. Selective cutting usually removes the largest, most valuable trees and may leave large-diameter, poor-quality, low-value trees. In each case, most of the trees that remain after the harvest are genetically inferior or physically defective. Neither method gives any thought to the composition of the future forest.

Chris Schnepf, University of Idaho Extension, www.forestryimages.org

In even-aged forests such as those in Pennsylvania, smaller-diameter trees are not necessarily younger trees.. It is more probable that these smaller trees are:
1. slow-growing species of the same age as different, fast growing species;
2. the same species of the same age but growing on an inferior Microsite; or
3. the same species of the same age but genetically inferior to their larger-diameter counterparts
Because slower-growing and poorer-quality trees are retained, high-grading diminishes the diversity and economic value of the future forest. Landowners may agree to high-grading because of a lack of knowledge about the practice and its undesirable consequences. High-grading also can be driven by short-term economic considerations. Immediate cash flow may be higher with high-grading, but potential environmental degradation and decreased future timber values will more than cancel the immediate cash advantage.
Stewardship requires that landowners consider the future consequences of high-grading when making a decision whether or not to accept the use of the practice on their land. Resource professionals and harvesters also have an obligation to look beyond the present when recommending forest management practices to landowners.
* Above information provided by the Pennsylvania DCNR Bureau of Forestry.

*Information provided by the US Forest Service "Crop Tree Management: Quick Reference" by Brenda L. Wilkins, Jan. 1994.