Minnesota’s jack pine forest type

April 20, 2007 at 5:49 pm Leave a comment

Products and Uses

Jack pine is used mainly for pulpwood, but also for poles and small sawlogs. It is moderately useful for deer food. Young trees may be heavily browsed where deer populations are high. Dense, young stands provide cover for snowshoe hares. Dense sapling and poletimber stands offer some wildlife shelter, but not as much as most other conifers. Older jack pine stands usually are less dense than other conifer stands, permitting the growth of understory shrubs and herbaceous plants offering wildlife food and cover.

Growing Conditions

Declining jack pine, Brainerd MN. Click for a better viewJack pine grows in extensive pure stands, but frequently is mixed with red and white pine, aspen, paper birch, and oak; less often it is mixed with black spruce, white spruce, and balsam fir. It grows best on well-drained loamy sands where the midsummer water table is 4 to 6 feet deep, but it is more common on dry sandy soils where it grows poorly, but better than most other species. It also is found on glacial eskers, sand dunes, and rocky soils. Jack pine does well on moderately acidic soils, but it will tolerate slightly alkaline conditions. It grows poorly in areas of shallow bedrock and heavy clay soil. A shade-tolerant species, jack pine is a pioneer species that typically colonizes burned areas and bare mineral soil. It usually is succeeded by more shade-tolerant species on all but dry, sandy soil.

Regeneration

Although jack pine is short-lived, stands sometimes survive up to 100 years. Individual trees may live for 200 years on good sites. Commercial rotations generally are 40 to 70 years. Mature trees in these stands range from 8 to 12 inches diameter at breast height (DBH).

On all but dry sandy soils, species other than jack pine are more productive and valuable for wood products. If your management goal is timber production, stand conversion to alternate species is recommended on these sites. In mixed species stands sufficiently stocked with more desirable species,Jack pine conesyou can make the conversion by harvesting the jack pine in several cuts. If desirable species are not well-stocked, convert the stand by clearcutting and planting alternate species.

Jack pine cones in parts of the range are serotinous: they remain closed at maturity and open only when exposed to intense heat (such as heat from a fire), but persist on the trees for years resulting in large accumulations of seed.

map showing range of jack pine
Range of jack pine.

In the southern part of the range, cones typically open as soon as they mature. Good seed crops occur at 3- to 4-year intervals starting about age 20, but the best seed production occurs on trees 40 to 50 years old.

Jack pine seedlings require full sunlight. Clearcutting creates the best conditions for regeneration, but seed tree or shelterwood systems may be appropriate depending on stand and site conditions. Clearcutting is recommended where a new stand will be established by planting improved seedlings, direct seeding, or scattering serotinous cones from high-quality trees. After clearcutting, branches bearing serotinous cones can be scattered on bare mineral soil. The sun’s heat near the ground surface will open the cones and release the seed. If the mature stand is not a suitable seed source, burn the site to destroy slash and plant or seed the area using a desirable seed source.

Jack pine savanna restoration site, Brainerd MNThe seed-tree system is a possible alternative for stands that have ten well-distributed, desirable quality seed trees per acre with an abundant supply of nonserotinous cones. After the harvest, burn the area to consume slash, kill competition, and prepare a favorable seedbed. Burn slash as soon as possible after harvest to minimize the risk of seed trees windthrowing before they cast seed. Jack pine slash requires a month of warm, dry weather to cure sufficiently to burn. Early spring fires permit seeding during the most favorable season, but late fall burning and seeding may be almost as effective if rodent populations are low.

Direct seeding may be successful where the water table is within a few feet of the surface or there is frequent precipitation during germination and early seedling development. Coat the seed with bird and rodent repellents and sow it at the rate of 20,000 viable seeds per acre. It’s best to seed in early spring to take advantage of snowmelt waters and spring rains.

You may need to plant where direct seeding failed or on deep, dry sandy soils. Bare-root seedlings should be planted only in spring, but container-grown stock can be planted into early summer. A 6- to 8-foot spacing usually is recommended.

Intermediate Treatments

Most natural jack pine stands are understocked; however, dense seedling or sapling stands may develop that will stagnate if not thinned. In very dense seedling stands (e.g., 10,000 trees per acre) it’s less expensive to mechanically clear strips about 8 feet wide and leave strips about 2 feet wide than to thin to produce 800 to 1,000 uniformly spaced crop trees per acre. Thin pole-sized stands if poles or sawtimber are desired. Because pulpwood is the main crop, pruning is not recommended.

Pests

Common insect pests of jack pine include bark beetles and jack pine budworm. Heart rot and shoestring root rot are important diseases.

To reduce losses, harvest stands by 50 years of age. Do not reproduce jack pine where the site index is less than 55. To maintain vigorous stands on good sites, thin regularly, removing suppressed and low-vigor trees while avoiding damage to residual trees. This reduces flower production and helps control both budworms and bark beetles.

To minimize budworm buildup, avoid open stands, open-grown wolf trees, and stands with suppressed trees. If budworms kill the tree tops, harvest the stand within a few years to avoid loss due to heart rot. Minimize bark beetle damage by maintaining vigorous stands, avoiding tree damage, and managing slash as described for eastern white pine. There is no treatment for shoestring root rot.

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Minnesota’s black spruce forest type Minnesota’s red pine forest type

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

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