Commercial Species and Stand Management Systems

Commercial Species Found in Wisconsin
In Wisconsin, hardwood trees are the most abundant, with maple-basswood, aspen-birch, and oak-hickory the most common (pie chart showing percentages—maple-basswood-35 percent, Aspen-birch, 18 percent, Oak-hickory, 18 percent, rest (16 percent) is softwood types). In 1996, a timber inventory counted about 9.8 billion trees in Wisconsin, an overall increase of 12 percent since 1983. Commercially important species totaled about 18.5 billion cubic feet of growing stock volume of which 4.4 billion were conifer and 14.1 were hardwood. Most softwoods also increased, except jack pine, which decreased since the last inventory in 1983. Aspen and paper birch have also declined since 1983. Sawtimber increased dramatically since 1983 by over 30 percent to 11 billion board feet. This growth trend is expected to continue as Wisconsin’s forests age. For more information on forest types in Wisconsin, go to:
http://dnr.wi.gov/forestry/assessment/WIforestsAtMillennium.htm

Silvicultural Systems
Did you know that of every 1,000 trees over ten feet tall in Wisconsin, only four will be harvested by loggers? At the same time, 98 new trees will grow past the ten-foot mark during the year. Therefore, in Wisconsin, annual wood growth exceeds harvest for most species. Silvicultural systems are practices used to regenerate tree stands after a harvest, either naturally or through artificial regeneration. The four common silvicultural systems used are clearcutting, seed-tree, shelterwood, and selection. The goals of these systems are to either create stands of trees of the same age (even-aged) or different age classes of trees (uneven-aged). Growing conditions and management objectives will help you or your forester decide which method is most appropriate.

Clearcutting: Complete clearcutting is harvesting every tree regardless of species or size. It creates the best site conditions for regenerating a stand of sun-loving trees like aspen, white birch or jack pine.

Clearcuts can vary in size and shape, accommodating habitat protection goals and aesthetic values. The practice helps regenerate trees that need full sun and grow best in even-aged stands. Although clearcuts may visually appear to be damaging to the landscape, there are sound biological reasons for using this practice under certain conditions.

A practice that is often confused with clearcutting, is the harvesting of only those trees with high market value, which is known as "high-grading." Through high-grading, genetically inferior trees will regenerate and take over the stand.

Seed-tree system: Considered an alternative to complete clearcuts, this method leaves trees scattered throughout a harvest stand in order to provide seeds for regenerating the entire area. Once the new forest is established, the seed trees can be harvested or left to grow. This system works only for species that produce wind-dispersed seeds. In most cases, five to ten seed trees per acre are left uncut. Site preparations to prepare seed beds are usually conducted. There are a number of disadvantages to this method, due to the lack of control for disease, wind damage, delays in seed crops, invasion by competing vegetation, spacing and stocking rate of reproduction. Although more aesthetically pleasing than clearcuts, this system is rarely used because of its disadvantages. However, careful attention to the challenges faced in seed-tree management can be successful while saving money normally spent on planting. The seed-tree system is used in red pine, white pine and white birch stands.

Shelterwood System: The shelterwood system is similar to the seed tree system, but the difference is that more trees are left, two to three harvests are made over the regeneration process, and the new stand is established under the partial canopy of older trees. In the first harvest, the best trees are left to grow and heavy thinning is conducted to stimulate growth and seed production. This cut can be eliminated if intermediate thinnings have achieved good results. Site preparation is also needed to prepare for seed germination. Several years later a release cut is made to stimulate new seedling growth. The final cut removes the remaining mature trees, leaving behind the younger same-aged trees to grow. This system is most appropriate where species can become established under partial shade and where the increased cost of several partial cuts can be absorbed. Several versions of this system include the Uniform method, where trees are harvested throughout the entire stand, the Group method, where groups of trees are harvested and the Strip method, where strips of trees in an alternating or progressive pattern are harvested. The shelterwood system is commonly used in white pine, red oak, yellow birch, white birch and hemlock stands.

Selection System: Individual or small groups of trees are harvested in the selection system. Trees of all sizes are harvested every five to ten years or so, aiming for selection of mature trees, damaged or unhealthy trees, proper spacing and thinning. The selection system, when properly conducted, produces a stand of trees with variable ages and sizes. The average quality of each remaining tree should improve before next harvest. Natural reproduction is expected, but planting new seedlings can help regenerate the stand. This system leaves the most forest cover, with little slash, or residue left on the ground. Some disadvantages of this system include the potential harm to remaining trees unless harvest is done very carefully. Another disadvantage is that the small volumes of wood harvested may not offset logging costs, and the shade-tolerant trees that are regenerated may be less desirable than other species. Additionally, care must be taken to ensure that gaps (small holes) in the overstory canopy are created above desirable seedlings to ensure that they develop into high quality trees. The selection system is commonly used in sugar maple, beech, hemlock and yellow birch stands.

The Value of Non-Commercial Trees in Your Woodland
There are stands of trees that have little or no commercial value. Yet people grow them because of their beauty and value as habitat as well as other more intangible benefits. Additionally, non-commercial stands can provide considerable benefits for the landowner — including reduced soil erosion caused by wind and runoff. Canopied forests also keep buildings cooler in the summer and protect from heat loss in the winter. Other benefits include aesthetic values, an increase in property values, and an effective noise muffler.

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