Minnesota’s eastern white pine forest type

April 20, 2007 at 5:33 pm Leave a comment

Products and Uses

Eastern white pine is used mainly for lumber. Although wildlife receive virtually no food benefit from older white pine stands, young dense stands may be used for shelter during inclement weather. Deer and rabbits browse heavily on white pine seedlings. In contrast to red pine stands, white pine (except in pure, dense stands) tends to have a better developed tall shrub and herb layer providing wildlife habitat.

Growing Conditions

Eastern white pine buds & foliage. Click for a better view.While white pine occurs in pure natural stands, it more frequently is a component of other forest types that may include red pine, red oak, hemlock, ash, and other northern hardwoods or conifers. It is most common on well-drained sandy soils and on droughty, loamy sands where it competes well with hardwoods. White pine grows well on stony loams, silty loams, and glacial tills with good or impeded drainage, but usually cannot compete with more aggressive hardwoods. The worst soils for white pine are clayey or poorly drained. Aspect and slope seldom restrict its occurrence.

White pine is intermediate in shade tolerance and may live 200 years or more. Seed production is generally good every three to five years, although 10 years or more may elapse without a good seed crop if cone beetle damage is present.

Regeneration

Rotations may be as long as 120 years for white pine, but 80 years usually is sufficient to produce sawlogs on good sites. Seedlings grow best under partial shade. Seedlings require at least 20 percent of full sunlight to survive, but may die from high soil surface temperature if there is full sunlight. White pine reproduces naturally from seed. Seeds will disperse at least 200 feet within a pine stand and more than 700 feet in the open.

Because white pine seedlings tolerate shade well, and to reduce blister rust risk, regenerating white pine under an existing canopy is often a good idea. This is done by partially removing the existing canopy, allowing sufficient light for white pine seedlings to thrive. This approach is depicted in the image below. (If a seed source is not present in the stand, underplanting will be necessary.)

A two-cut shelterwood system probably is the most reliable method for natural regeneration. Ten years prior to the final harvest remove 40 to 60 percent of the overstory (no more than 30 to 40 percent of the basal area), preferably in the year before or during a good seed year. Harvest during snowless months to scarify the site and expose mineral soil. Remove hardwood regeneration during the harvest since these trees may seriously compete with pine seedlings.

White pine advance regeneration under thinned red pine. Click for a better view.After 5 to 10 years, if white pine seedlings are abundant, clearcut the residual overstory. (Delay this harvest until the new white pines are 20 to 25 feet tall if white pine weevil is expected to be a problem.) If white pine regeneration is not satisfactory, you may need to again thin the overstory, control advance hardwood regeneration, and wait another 5 to 10 years before the final harvest. Consider planting white pine seedlings to increase the density to 500 to 600 seedlings per acre.


Range of eastern white pine.

Mechanical site preparation and planting are required on bare land or in white pine stands that do not naturally regenerate. Plant 2-0 or 3-0 seedlings at rates up to 600 to 800 trees per acre (closer where heavy white pine weevil damage is expected). Plant under a light forest canopy to reduce weevil and white pine blister rust damage.

Intermediate Treatments

You do not need to thin white pine seedling and sapling stands, but if a hardwood overstory develops, partially remove it to maintain 50 percent of full sunlight on the white pine. When trees average 6 to 8 inches DBH, begin thinning and remove the hardwood overstory. Basal area after thinning should be about 100 square feet for young stands and 150 square feet for older stands. Maintain at least a 35 percent live-crown ratio on crop trees. Since white pine has persistent branches, you will need to prune to a height of 17 feet to develop clear wood. Prune in the dormant season, removing limbs only if they are less than 2 inches in diameter. Frequent light prunings are preferred to a single heavy pruning. Depending on local markets, pruning may not be economical.

Pests

White pine blister rust is a serious disease problem. Major insect pests include white pine weevils, bark beetles, and pine sawflies. White pine seedlings can also be heavily browsed by deer.

Your local forester can advise you concerning the blister rust hazard in your area. Don’t plant white pine in high-hazard zones for blister rust. In medium and low-hazard zones, prune lower branches early to minimize the disease. For further information on how to manage white pine blister rust see the U.S. Forest Service fact sheet. Weevil and blister rust damage can be reduced by regenerating white pines under an overstory of hardwoods and releasing them slowly until the pines are about 20 to 25 feet tall. Then remove the overstory. For more information on pine weevils see this  link to U.S. Forest Service pine weevil fact sheet.

To avoid bark beetle damage, do not harvest or thin the stand from January through August unless you destroy all slash greater than 2 inches diameter within three weeks of cutting. Slash can be destroyed by piling and burning, by chipping, or by burying. Avoid wounding residual trees during thinning. If trees are damaged by fire, storms, or logging, harvest them, remove the logs from the woodland, and destroy the slash within three weeks. For more information on bark beetle management see DNR pine bark beetle management.

Sawflies are common defoliators on white pine, but usually do not cause serious damage. If control is needed, chemical sprays will be required, since microbial insecticides are ineffective. For more information on pine sawflies got see the forest service pine sawfly fact sheet.

Deer will often browse the buds of young white pine in the winter. This often results in non linear growth of the tree, reducing the financial value of the tree. Bud capping is a simple solution to winter deer browsing, see the link to the DNR field tip on how to bud cap.

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

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