Timber harvest methods
Forests require disturbance to regenerate. How, what, when and why can be management decisions with a purpose, or they can be subject to random natural events.
Michigan forests represent a mind-boggling range of diversity. Levels of diversity vary in time and across the landscape. Disturbance is a crucial component of diversity, and timber harvest provides a measure of control of where and how disturbance occurs.
Given the diversity of Michigan forest types, it is not surprising that a range of forest management and timber harvest systems have been developed that employ inherent ecological characteristics of those forest types as guidelines.
There are three major groups of timber harvest practices; clearcutting, shelterwood and selection systems. While each are different and are applied to specific forest types, they have three things in common:
- They provide wood fiber for thousands of every-day products.
- They establish environmental conditions that encourage the natural regeneration of the forest.
- They enhance the ecological, economic and social values of the future forest.
Selection harvesting may be the most misunderstood system and is certainly the most complex. When stands of trees become overly dense, forest health risks increase. Removing the higher-risk trees and leaving the trees with higher potential improves the quality and character of the forest. The partially-opened canopy allows enough light to accelerate individual tree health and vigor, and allows seedlings to grow. The young trees eventually replace the older trees as the older trees either die or are harvested.
The “catch” with the selection system lies in the ability of tree seedlings to tolerate shade conditions on the forest floor. Given the diversity of Michigan’s forest, it should be no wonder that some tree species will grow in the shade and others will not. For those shade-tolerant tree species, forms of selection management work well.
The “dark side” of selection management is when the wrong trees are “selected” for harvest. High-grading, diameter-limit cutting, and other unscrupulous practices can do serious damage to a forest. Secondly, selectively harvesting a forest type that cannot regenerate under the residual shady conditions can also inflict damage.
Clearcutting is the solution to forest types whose seedlings or sprouts require full sunlight. Seeds and buds respond well to the warmed ground. The abundance of light produces excellent growth, some of the fastest we have. Species such as aspen, paper birch and jack pine require full sunlight.
The “catch” with clearcutting is appreciating how nature did clearcutting before there were people to wield chainsaws and harvest processors. Wildfire, wind, insect outbreaks and floods were common ways nature employed to level large tracts of Michigan forest in order to allow sun-loving forests to regenerate.
With our tremendous dependency upon forests, the losses from these natural events are typically regarded as negative and something to avoid, if possible. Clearcutting is an economical and ecologically viable way to reduce the negative effects of natural catastrophes at the same time accommodating the ecological requirements of these kinds of forest types.
The shelterwood system lies somewhere in between the visual extremes of clearcutting and selection management. The parent forest is removed in several stages, with each stage successively establishing optimum environmental conditions for tree regeneration and then nursing the regeneration along to a point where the remaining parent forest can be harvested. Red oaks and white pine stands will often benefit from shelterwood harvesting.
Forest management and timber harvest systems utilize a very deep reservoir of forest research and experience. Practices are well-grounded in the applied ecological sciences, despite how some might appear to the casual observer.
The notion that tree cutting is “bad” has become a culturally ingrained misconception. Wood is a renewable natural resource, providing an edge over any other raw material. The harvesting and processing of wood products also incurs the least amount of negative environmental impact, by any measure.
All trees die. Using some of them to supply our needs is a good thing. In the USA, each person uses about 9-10 pounds of wood per day. Yet, in Michigan, we have huge amounts of forest growth, among the greatest accumulation in the nation. Forest-based industries provide markets for wood products, which expand forest management opportunities. These industries have become especially important in our rural areas.
Managed forests provide for healthier forests and produce more of all the values we want from forests. Many environmentally-conscious groups somehow twist forest harvest into a negative enterprise. There are many great environmental causes to choose from these days, but opposing tree cutting is just not one of them.
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