Minnesota’s northern hardwoods forest type

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.

Mel is the Extension Forestry program leader. He’s based on the St Paul campus.

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7 Comments

    1. Finding seed may be difficult, but you may be able to find seedling stock grown from source-certified seed. I know that the MN state forest nurseries offer source-certified seed and my understanding is that with the coming nursery closure, some commercial nurseries may begin to do so (if they don’t already) as well. I suggest contacting the MN Nursery and Landscape Association for a list of nurseries in your area that have the seed you’re looking for. MNLA’s contact info is at http://www.mnla.biz/content.asp?pl=146&contentid=146
      -eli

  1. I have a northern hardwoods forest that is predominantly mature sugar maple and basswood in the overstory, with some red oak and aspen also in the overstory. The mix is approximately 60% sugar maple, 30% basswood, 10% red oak/aspen. This stand is in the Grand Rapids, MN area. The sugar maple is of poor quality with many frost cracks.

    I would like to convert the composition to 30% sugar maple, 30% basswood, 20% red oak, 20% aspen for wildlife purposes. I realize it will take a long time to do this. Any recommendations?

    1. Great question Jim. You may want to consider different strategies to regenerate oak and aspen in this stand. Oaks can tolerate moderate shade, especially as seedlings. To regenerate oaks you may want to remove a portion of the canopy around Sommer large-crowned, mature oaks. This will allow enough light to penetrate to allow establishment of the oak to expand it as a component of the stand, while reducing establishment of less shade-tolerant species like aspen, which could outcompete it. To determine how much oak to remove and what site prep may be needed to promote natural regeneration (from seed), you should have a forester walk the stand.

      For aspen the approach is similar in the sense that you focus on areas around existing aspen, but you would harvest all trees to form relatively large, open gaps because aspen will not grow well under shade.

      These are general strategies, but I would suggest having a forester walk the stand with you. The success of either of these treatments, and details of their implementation, will vary with the native plant community, soils, current stocking, and many other factors. You can find a forester on or site at http://z.umn.edu/stewmap.
      Hope this helps.
      -eli

  2. I have never been able to get aspen to grow except in close to full sun. I’ll get lots of volunteers after cutting, but they get about 4-8 feet tall, and the leaves get a white fungus on them. The next year they try again, but soon after they are a stick.

    I manage 15 acres of mixed poplar/spruce bush for firewood. Intially I took out only the mature and senescent trees, but I wasn’t getting any young poplar even in areas with 50% blue sky. So now I ‘clear cut’ a clearing that is roughly an acre. This provides 2-3 season’s wood.

    Here, the normal succession is grassland, poplar, spruce, fire. Poplar groves grow into grassland by suckering. As they die, they are replace by spruce, which need the shade when small. Poplar woods are often damp enough that they don’t burn well, but the understory of a spruce wood is full of dry kindling, and ‘fire ladders’ up the dead twigs on the lower trunks.

    One thing I’ve found in setting out seedlings: The survival rate is a lot higher if you plant a stick with each tree. You can spend money on survey stakes, or if you are cheap like me, you can take apart pallets and run the boards through the table saw.

    Sticks do several things for you:

    1. It reduces the number that get stepped on.

    2. It seems to reduce the number that get eaten by deer.

    3. It allows you to better evaluate the survival.

    4. When you are planting it makes it easier to check your spacing.

  3. Thanks for the information, Eli and Sherwood. I like the clearcutting strategy for the aspen. That makes sense.

    Follow up question. Let’s say I want to continually increase the area occupied by aspen. Would I do a follow up clearcut after 10-15 years in the aspen and also increase the area cut from 1 acre to 2 acres (for example)? I get what Sherwood is saying. The aspen will shoot up but if they’re not getting enough light, they’ll die in a few years. If I keep removing the border trees that are intercepting sunlight, do you think that would help the aspen get established?

    1. Yes. Go find an abandoned farm with an aspen grove on one edge. You will often see a whole bunch of saplings in a band about 20-50 feet wide on the field edge of the grove. It will happen on the north side of a grove too, but even with the light of the north half of the sky, they don’t grow quickly

      If you have a mix of woodland and cleared land, and that cleared land is next to an aspen grove, you can encourage this behaviour by using a plough and cutting the roots 20 feet away from the existing trees Root injuries encourage suckering.

      If you want to do this as a reforestation technique, I’d suggest doing a 300 foot wide clearcut, starting from the north end, and moving south by 100 feet a year. (This would be cutting about 1.5 acres a year. You could do 600 x 60 feet instead.

      You may want to leave a few outstanding trees as seed trees for the next generation after the aspen.

      Another tree that is becoming more common here and loved by the birds are mountain ash. (Genus sorbus, no relation to green ashes genus fraxinus) It’s moderately shade tolerant. You may want to look at planting 5 needle pines. Most of them are shade tolerant. Swiss Stone Pine and Korean pine produce edible nuts. Eastern White Pine is one of the fastest growing conifers.

      If you replant by hand (not usually necessary with aspen) cut your stumps on a slope to the east, and plant your seedlings on the east side of the stump. This gives it good light and just a touch of shade during the hottest part of the day. The stump directs water toward the little tree, and protects it from getting stepped on. As the stump decays, nutrients are available to the seedling.

      Look around you. Find an area that is a few degrees warmer, and a bit drier. Local climate change prediction is a game of blind man’s bluff, but warmer and drier is the way to guess. Go see what grows there, but doesn’t where you are. Look for small changes 2 degrees warmer 10% more precipitation.

      In general what grows on the south side of a hill will move up, and possibly over the top.

      Plant a mix. Diverse econsystems are more resiliant.