Forest regeneration is the process by which new tree seedlings become established after forest trees have been harvested or have died from fire, insects, or disease. Regeneration is key to sustainable forestry and can be accomplished through two basic approaches:
- natural regeneration, which occurs when new seedlings or sprouts are produced by trees left on or near the site (as with aspen)
- artificial regeneration, more commonly known as tree planting
Timing is important in the regeneration process. Prompt reforestation can be critical if a landowner’s objective is timber production or a forested habitat. Every year that a forest is understocked means a loss in timber growth. Moreover, delaying regeneration can allow brush, grass, or other undesired vegetation to take over a site, making the process of establishing desired trees difficult and expensive. Also, many states’ forest-practice laws require reforestation within a few years of a timber harvest.
Determining whether to renew a forest through natural regeneration or tree planting depends in part on the section of the country in which a forest is located. Landowners in the eastern United States often prefer to establish new timber stands by promoting natural regeneration rather than by intentionally planting specific trees. Through natural regeneration, existing trees reproduce themselves and develop into a natural community based on the site conditions. Rural property owners can create conditions to promote natural regeneration of desired species. Often, creating such conditions is a more practical option than developing an artificial plantation of hardwoods. Natural regeneration is usually less expensive to initiate, uses trees that are proven to grow in the native soils, and can be established in high densities that produce straight, high-quality stems.
In the western United States, the decision to rely on natural regeneration or plant trees depends on how a forest owner is managing a stand. Most landowners who use the clear-cut silvicultural system follow a harvest with prompt tree planting. Landowners using the seed-tree silvicultural system also often end up doing some planting, at least on a supplemental basis, particularly when natural regeneration is not as successful as anticipated. By contrast, landowners who use the selection silvicultural system or the shelterwood silvicultural system tend to rely on natural regeneration, though they may undertake some supplemental tree planting, particularly to establish desired species not currently present on the site.
Whether a landowner decides to rely on natural regeneration or plant trees, it is important to monitor the results of that decision. Measuring forest regeneration success by assessing the stocking rates of sample plots is critical. If acceptable numbers of new tree seedlings are not established promptly, the switch to planting or the act of planting additional trees becomes progressively more expensive.
The following articles provide more information about forest regeneration options:
- Forest Renewal through Natural Regeneration
- Evaluating Forest Regeneration Methods for the Northeastern United States
- Tree Planting for Forest Regeneration in the Eastern United States
- Tree Planting for Forest Regeneration in the Western United States
Chris Schnepf, University of Idaho
Kristi Sullivan, Cornell University