Natural regeneration: Growing a new stand from natural seedlings

April 28, 2007 at 7:26 pm Leave a comment

Red oak seedlingA stand should be regenerated when most of its trees are economically mature, when it is stocked with undesirable tree species or poor quality trees, or when it is greatly understocked. Tree stands may be reproduced through natural or artificial means (planting) or by a combination of the two. The choice of how best to reproduce a stand depends on the tree species involved, financial considerations, and management objectives.

Natural regeneration

Depending on the species, trees may reproduce naturally by seeds, root suckers, stump sprouts, or layering.

Seeds

When regenerating stands by natural seeding, it is important that you know how the species you wish to encourage disperses seed, how far its seed travels, how abundantly it produces seed, and what type of seedbed is needed for germination. This information will affect how you harvest and prepare the site.

Tree seeds are dispersed in a variety of ways. Aspen and cottonwood seeds are covered with a cottonlike down and may be carried several miles by the wind. Maple and pine seeds have wings allowing them to glide in the wind. Cherry seeds frequently are dispersed by birds that eat the cherries and drop the seeds far from parent trees. Walnuts, acorns, and pinecones often are carried away and buried by squirrels. Seeds from willows and other shoreline species may be dispersed by water.

Jack pine seedling and cones near Baudette MN

esagor photo. Click for original.

Very few of the seeds produced grow into seedlings. A number of conditions must be met for natural seeding to be successful. In addition to an adequate supply of viable seed, there must be a receptive seedbed. For most species, this means that mineral soil must be exposed so the seed can get enough moisture to germinate and grow. Soil temperatures must be high enough so seeds will germinate, but not so high that the seedlings will be killed. Rodent predation of seed, available moisture, and vegetative competition also affect success or failure.

 

Most hardwood species reproduce easily from seed when conditions are favorable. However, natural reproduction of conifers from seed often is erratic and unpredictable. Jack pine and black spruce can successfully regenerate from seed when seedbed, moisture, and temperature conditions are right. These two species often store seed in cones on the tree for many years until heat, as from a fire, opens the cones and releases the seed. For other conifers such as red (Norway) pine, white pine, white spruce, and tamarack, viable seed crops are unpredictable and successful stand establishment does not always occur.

Root Suckers

illustartion of root suckersSome hardwoods (e.g., aspen and black locust) regenerate from root suckers as well as from seed. A tree that grows from a root sucker is genetically identical to the parent tree and is called a clone. Suckers usually develop after a parent tree has been cut down. A single parent tree may produce several hundred suckers, creating a dense new stand. The number of suckers may be reduced if the parent tree is in poor health or if timber harvesting causes root system damage or soil compaction.

Stump Sprouts

illustration of stump sproutsOther hardwoods, including oak, basswood, birch, and maple, sprout from stumps as well as grow from seeds. Relatively young stumps, cut close to the ground in late fall or winter when there are food reserves stored in the roots, sprout the best. Stumps often send up numerous sprouts, but these usually thin naturally to two or three main stems. You can speed up this process and encourage the strongest stump sprouts by cutting the others when the sprouts are five to ten years old.

Layering

illustration of layering

Layering occurs when a buried branch takes root and develops into a new tree. The lower limbs of black spruce, balsam fir, and northern white-cedar sometimes touch the ground and become covered with organic matter. Layering is not an important reproduction method in forests, but can provide additional northern white-cedar for deer browse on suitable sites.

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

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