Minnesota’s northern hardwoods forest type

April 20, 2007 at 5:53 pm Leave a comment

Products and Uses

The northern hardwoods forest type includes numerous tree species. Sawlogs and veneer logs are the major wood products, but some species also are harvested for pulpwood. Maple syrup is made from sugar maple sap. Wildlife found in a northern hardwood forest may include deer, bear, squirrel, ruffed grouse, and woodcock.

Growing Conditions

Species composition of a northern hardwood forest varies by site and geographic range. Species may include sugar maple, American basswood, white ash, black ash, yellow birch, red maple, and elms. Occasionally aspen, paper birch, balsam fir, and northern red oak are important. Beech and eastern hemlock occur from Michigan eastward.

Sugar maple, beech, hemlock, and balsam fir are very shade tolerant; basswood is tolerant; yellow birch, white ash, red maple, and red oak are moderately tolerant; black ash, paper birch, and aspen are intolerant. Elms, black ash, yellow birch, red maple, eastern hemlock, and balsam fir survive best on high-moisture sites. Sugar maple, white ash, basswood, and beech generally are confined to better drained soils. The best timber is found on moist, well-drained, fertile, loamy soil. The poorest sites occur on soils that are infertile, dry, shallow, or swampy.

map showing range of sugar maple
Range of sugar maple.

Regeneration

Northern hardwoods can be regenerated by a wide range of systems depending on the species to be favored. If high-quality, very shade-tolerant species are desired, use single-tree selection or group selection methods. After a selection harvest, the residual basal area should be approximately 80 square feet per acre.

If you prefer an even-aged stand dominated by sugar maple, use a two-cut shelterwood system. Harvest in winter and leave 60 percent crown cover after the first harvest. Make the second cut after advance regeneration is 2 to 4 feet high. If you prefer a greater variety of species, use a two-cut shelterwood system, but first eliminate all reproduction present before cutting, harvest in any season except summer, scarify the site during harvest, leave 70 to 80 percent crown cover, remove undesirable seed sources, and make the second cut after advance regeneration is 2 to 4 feet high.

Planting seedlings is rarely necessary, but is appropriate for open fields or under a shelterwood to change the species composition. In open fields plant only in fertile, well-drained soils. Thoroughly disk before planting, plant tap-rooted species such as white ash and northern red oak, plant only when there is good soil moisture, and control weeds for 1 to 3 years after planting. Under shelterwoods, kill undesirable understory plants and plant in the most open areas immediately after site preparation.

Where aspen is mixed with more shade-tolerant northern hardwood species, decide whether to encourage either aspen or the other species. If there is an overstory of aspen and an understory of hardwoods, you can favor the aspen by clearcutting the stand to stimulate root suckering. Favor hardwoods by removing the aspen when the understory hardwoods are 1 to 3 inches DBH, taking great care to avoid damaging the hardwoods. If the aspen has little commercial value, consider killing it with herbicides and letting it stand.

If aspen and other hardwoods are of equal size, aspen can be favored by clearcutting the stand. If aspen is scarce but desirable, follow the harvest with burning or shallow scarification to create an aspen seedbed. To encourage hardwoods, thin or harvest the stand according to the stocking chart for even-aged management of northern hardwoods.

Intermediate Treatments

When following the single-tree selection system, use Table 8 to determine the approximate basal area and number of trees to leave after each harvest. Remove poor quality trees and undesirable species during the harvest.

Pests

Insect pests vary due to the diverse species composition of the northern hardwoods forest type. forest tent caterpillar and a fall defoliator complex (a mixture of up to ten insect species) cause the most problems. No cultural controls are available. Chemical insecticides and BT are effective.

Nectria canker can be common, especially in uneven-aged stands. Reduce damage by maintaining healthy stands and removing infected stems. Sapstreak of maple and heart rots also are serious. To minimize damage from these diseases, reduce damage to roots and stems during cutting operations by using rubber-tired skidders and by harvesting during winter or dry seasons. Remove diseased trees as soon as possible.

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News and information of interest to Minnesota woodland owners. Sister site to MyMinnesotaWoods.org.

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