Questions Frequently Asked About the ATC Study
What is the study?
This study is a joint effort of the USDA Forest Service's Alaska Region and the Pacific Northwest Research Station. The study has an experimental component and a retrospective component. The experimental study will apply nine different silvicultural treatments to large (40-60 acre) units and the set of nine treatments will be repeated in several areas on the Tongass National Forest. Because results from the experimental study will not be available for some time, a retrospective study of past partial cutting and its effects is also planned. Results from this study will be available to guide managers within 3-5 years.
What is the purpose of the study?
The study is being done to see if harvest methods other than clearcutting can be effectively and economically done in southeast Alaska. The study is being undertaken in response to the 1992 direction by the Chief of the Forest Service to reduce the amount of clearcutting and to address the concerns of some groups who feel clearcutting reduces wildlife habitat, damages fish habitat, and is visually undesirable.
What are the objectives of the study?
The effects of these harvest treatments on a number of resources will be studied. Included are: damage to the residual trees, amount of soil disturbance, effects on soil stability, ground water, stream sedimentation, wildlife, birds (mainly migratory birds that only utilize the Tongass for a part of the year), economics, spread of insects and diseases, and the public's perception of the different harvest methods.
Of great concern is the damage to the residual trees because the trees in southeast are thin-barked and easily damaged by logging activities. These residual trees are the ones we are counting on to provide specific conditions or structure in the future. If these trees get damaged and infected with disease, they may not live as long as hoped for and our objectives won't be met. There are also several diseases that can be transmitted from the residual trees to the new trees that will come in after harvest. The rate and intensity of this disease spread is also of concern.
What are the treatments?
A total of nine harvest units at least 40 acres in size make up a study block. Each harvest unit will receive a different harvest treatment. Initially, there will be three study blocks located across the Tongass - one each on the Ketchikan, Stikine, and Chatham areas.
The nine harvest treatments are:
- No harvest.
- Clearcut.
- Leave 5% of the trees equally spaced across the unit.
- Leave 25% of the trees more or less equally spaced across the unit.
- Leave 75% of the trees more or less equally spaced across the unit.
- Leave 25% of the trees in small group ranging in size from 1/2 to 2 acres in size. Harvest all of the trees between these groups.
- Harvest small groups ranging in size from 1/2 to 2 acres in size. All trees will be harvested in these groups. In between these groups, leave 1/3 of the trees more or less equally spaced. The net result is leaving 25% of the total number of trees in the unit.
- Harvest 25% of the total trees. Create small gaps ranging in size from 1/2 to 2 acres in size. Cut all trees in these gaps. Do not harvest any trees between the gaps. The net result will be to leave 75% of the total number of trees in the unit.
- Harvest 25% of the total trees. Leave small unharvested groups ranging in size from 1/2 to 2 acres in size. In between these unharvested groups, remove 1/3 of the trees more or less equally spaced across the unit. The net result will be to leave 75% of the total number of trees in the unit.
Why include a clearcut treatment? Aren't there enough existing clearcuts to study?
In order to accurately determine changes resulting from timber harvesting, we need to know the conditions on a site prior to treatment. We don't have the detailed pretreatment information necessary on existing clearcuts. Also, in order for an experiment to be statistically valid, treatments must be assigned to the units at random, prior to treatment.
Why were these particular treatments chosen?
The chosen treatments emulate stand structures that occur in native forests in southeast Alaska. These patterns result from a variety of disturbance events, ranging from the death of a single tree from fungal attack to large-scale blowdown during violent windstorms. Medium-scale disturbances often leave patches of trees unaffected or may only remove a small group of trees. The treatments vary in both disturbance intensity and disturbance pattern.
Why use helicopters to yard when cable systems are more commonly used in southeast Alaska?
Some of the study treatments could be easily harvested with common cable yarding systems. A few of the treatments are possible only with helicopters or tractors. In an experiment such as this, all treatments must be harvested the same way, otherwise it is impossible to determine what caused the observed response--the treatment or the harvest method. We aren't suggesting that helicopters are the only suitable method for partial cutting, just that they are the only system that can accomplish all of our treatments.
Are similar studies underway elsewhere, or have they been tried in the past? The DEMO study in Oregon and Washington has similar objectives and treatments, but it focuses on Douglas-fir/western hemlock forests and will not be applicable to our region.
