Timber harvesting is often a controversial issue. A forest provides many different benefits, and preferences for its use vary from person to person. Controversy about timber harvesting often escalates because most people (forest landowners and the general public) know little about the process and its role in maintaining sustainable forests.
With proper planning and careful management, timber harvesting can be very beneficial by helping to maintain a vigorous, healthy and productive forest. However, it is essential when planning a timber harvest to consider potential consequences such as the species mix and the quality of the trees left, and avoid negative impacts such as erosion.
Harvesting timber is correctly done when it focuses on the what is left after the harvest, rather than the timber which is removed.
There are several different harvesting methods, including:
Clearcut – a harvesting and regeneration technique that removes all trees, regardless of size, on an area in one operation. In Pennsylvania, a clearcut can be an effective tool to regenerate a new forest of shade intolerant species like black cherry, aspen or yellow poplar.
Croptree – a thinning directed solely at those trees identified as crop trees, trees which one wishes to encourage. Only those trees competing directly with a crop tree are removed, improving the growth of the crop trees.
Group Selection – removes trees in 0.1 to 1.0 acre areas to create openings in the forest canopy; this mimics the opening of the canopy by the death of individual trees in an old growth forest.
Improvement thinning – cutting poorer quality and defective trees to foster growth in quality residual trees.
Shelterwood – removes both small and some large trees. The trees left serve as a seed source and the harvest favors tree species that require less than full sunlight to regenerate.
Thinning From Above – a diameter-based thinning reduces the stock to about 60% by removing all trees larger than a calculated diameter. It is also called high-grading. In an even-aged forest (which includes most of our forested land), this resembles eliminating the best specimens from a litter of dogs and breeding only the runts.
Some additional harvest systems may be demonstrated including removing trees to achieve specific densities relative to the initial undisturbed stand, and thinning from Below or the Middle by removing specific diameter classes.
The term, “selection — or selective — cutting” doesn’t really describe a method of cutting, but rather that someone has designated trees for harvest. Often the term is used to ‘sell’ the concept of harvesting to reluctant owners who usually then discover that only the best trees were ‘selected’ leaving undesirable trees in its wake.
Across Pennsylvania there are at least six Timber Harvesting Demonstration Areas whose purpose is to introduce landowners and the general public to the different methods of timber harvesting along with the benefits and consequences. Initial data collected before harvest and just after the harvest provides information on plant and animal species diversity, residual forest conditions, mortality, and economic value of each treatment. Efforts to monitor and document long-term impacts of each treatment are on-going. Each demonstration site has signage, brochures, and scheduled tours available to help you understand different harvesting strategies and the results.
The demonstration sites provide 4 to 6 examples of a number of different methods of harvesting woods. Each also has a Control Area, an untreated area used as a standard for comparison against the results of treatments on the other blocs. Many demonstration sites also have a Deer Exclusion Fence adjacent to the cutting treatments. This 20 foot square area is designed to demonstrate the effect of uncontrolled white-tailed deer browsing outside the fenced area.