Silvicultural Alternatives to Clearcutting Study

IN 1994, the Alaska Region of the USDA Forest Service and the Pacific Northwest Re-search Station (PNW) began a long-term study entitled "Silvicultural Alternatives to Clearcutting in the Old-Growth Forests of Southeast Alaska." This study was started in response to then Chief of the Forest Service Dale Robertson's Ecosystem Manage-ment initiative and his direction to reduce the amount of clearcutting on national Forest System Lands. Cooperators include Oregon State University and Humboldt State University.

Past research efforts have focused on the effects and economics of clearcutting but there is very little research on, or experience with, alternative silvicultural sys-tems in southeast Alaska such as seed tree, shelterwood, overstory removal, and se-lection. Results from this study will help fill this information need and assist natural resource managers in choosing management alternatives by providing essential information on the costs and benefits of adopting these alternative systems.

This study includes an experimental test of eight silvicultural systems ranging from even-aged management with clearcutting to uneven-aged systems employing single-tree or group selection. A total of three blocks have been located across the Tongass, a block being one replicate of the eight silvicultural systems being studied. The eight systems used in this study does not mean that they are the only systems being considered for use on the Tongass. Rather, the eight systems will create a broad range of conditions that could occur following timber harvest or any other distur-bance event such as windthrow, landslides, or mortality from insect or disease out-breaks. Effects to, and response of residual trees, understory vegetation, ground-water, slope stability, birds, and headwater streams will be measured for a number of years following timber harvest.

The Hanus Bay site is the first of these three blocks. Hanus Bay is on the Sitka Ranger District near the northeast corner of Baranof Island. The sale was completed in 1997.

The second treatment block is on the Petersburg Ranger District of the Stikine Area, on Kupreanof Island. It is planned for harvest in 1999 or 2000. The third treat-ment block is located on the Craig Ranger District of the Ketchikan Area, on Prince of Wales Island and is planned for harvest in 2000 or 2001.

Due to the nature of the experimental portion of this study, preliminary results won't start becoming available until several years after timber harvest and will continue for many years into the future. In the interim, the Alaska Region continues to consider and utilize alternative silvicultural systems and apply the system that will best meet management objectives and create the desired future conditions.

Study Plan Summary

Introduction
The USFS has committed to the concept of ecosystem management and has vowed to reduce the use of clearcutting. Rese mandates have created an information crisis: much is known about the ecological effects, economics, and social impacts of clearcutting, but there is little documented experience with other silvicultural systems in southeast Alaska. Alternative silvicultural systems hold the promise of sustained timber production with superior protection of associated resources, but this promise needs rigorous testing.

In a joint effort, the Pacific Northwest Research Station and the Alaska Region of the USFS are establishing an interdisciplinary study of ecosystem and social responses to alternative silvicultural systems. The project has two parts: a short-term retrospective study and a longer-term, operational-scale, experimental study. Results from the experimental study will be definitive and reliable, but we recognize that it will not yield quick answers to all of our questions. To provide interim guidance to land managers, we will extend the experimental study with retrospective studies of forest ecosystem responses to natural or human-caused disturbances.

Ecosystem and social responses to be evaluated include: stand dynamics, understory plant diversity and productivity, tree damage agents, deer habitat quality, avian diversity and abundance, stream ecology and biogeochemistry, slope stability, snow accumulation and persistence, economics, landscape aesthetic qualities, and recreational values. All of these responses can be addressed in the experimental study, but the retrospective approach is limited and will be most useful for quickly answering questions about changing ecological conditions and resources, stand dynamics, understory vegetation response, and pest and pathogen dynamics.

This integrated set of studies is meant to supply information needed to select appropriate systems for managing late-successional stands on commercial forest land in southeast Alaska. This project aims to fill gaps in our knowledge about the application and effects of alternatives to clearcutting. The principal users of this information will be USFS personnel managing the hemlock-spruce forests of southeast Alaska and interested members of the public.

Study Objectives
Biological:

• Determine how alternatives to clearcutting (ATC) affect the survival and growth of remaining overstory trees.
• Determine how ATCs affect new tree germination, establishment, and growth.
• Determine how ATCs affect understory plant diversity and abundance, understory productivity, and the nutritive quality of important wildlife forage species.
• Monitor tree damage that occurs during timber-harvesting.
• Monitor post-harvest tree damage due to wind, dwarf mistletoe, fungi, insets,and other agents.
• Measure the diversity, abundance, and reproductive success of breeding birds in different ATC treatments.
• Quantify the transport of food sources such as aquatic and terrestrial invertebrates and particulate organic matter from streams within ATC units to downstream fish-bearing stream reaches.
• Monitor changes in aquatic invertebrate community composition in headwater streams following ATC treatments.

Physical:

• Evaluate the impacts of clearcutting and alternative silvicultural systems on soil water levels, soil movement, sediment production, and slope stability.
• Determine ATC treatment effects on light availability and microclimate under forest canopies.

Social:

• Identify and document technical and operational problems encountered while implementing alternative silvicultural systems and develop management guidelines based on successful problem resolution or prevention.
• Determine the economic costs of planning, implementing, and monitoring ATC treatments.
• Evaluate the aesthetic effects of silvicultural alternatives.
• Determine the social acceptability of alternatives to clearcutting.

Experimental Study Design

Three favors and their interactions will be tested: the stand density retained after timber harvest, the spatial pattern of the retained trees (uniform vs. patchy), and the size of patches (gaps or uncut reserve areas). Stand density will be measured as total basal area per unit area and treatment levels will be defined in terms of the percentage of initial stand density retained after timber harvest. Post-treatment densities will range from 0 to 100% of the initial stand density (clearcut and uncut control, respectively), with three intermediate densities.

We will test three spatial patterns of the retained trees, holding the stand-level density constant. In one pattern, retained trees will be uniformly dispersed throughout the stand, another pattern will have circular, uncut patches or reserveswithin a uniform matrix, and the final pattern will have circular patches or gapscut into the uniform matrix. The matrix density will vary according to the desired stand-level density, but the number, size distribution, and total area of patches will be the same across all patch treatments. Three size classes of patches will be created with diameters equal to 1-, 2-, and 3-times the average height of the surrounding stand overstory. For an average tree height of 104 ft., this would yield patch sizes of 0.2, 0.8, and 1.8 acres.

This design yields nine treatments:

1. A conventional clearcut
2. A clearcut with 5% of the basal area reserved in isolated single trees
3. Individual tree selection retaining 25% of the basal area
4. Individual tree selection retaining 75% of the basal area
5. An uncut control
6. 25% of the stand retained in uncut patches, with clearcutting in the surrounding matrix (total retention 25%)
7. 25% of the stand retained in uncut patches, with individual tree selection (1/3 removal) in the surrounding matrix (total retention 75%)
8. A group selection cut of 25%, with additional individual tree sele*ion (2/3 removal) in the surrounding matrix (total retention 25%)
9. A group selection cut of 25% of the basal area, with no cutting between groups (total retention 75%)

Research Sites

In the initial phase, one block (replicated treatment set) of the experimental study will be established on each Area of the Tongass National Forest, for a tool of three blocks. Establishment of three additional blocks may be considered if funding becomes available.

We have identified approximately 200 potential retrospective study sites throughout southeast Alaska and additional sites continue to be found. Over the expected 3-year life of the retrospective study we will intensively examine 25-35 of the most promising sites.

Cooperators

The PNW Research Station Forestry Sciences Laboratory (Juneau), the USFS Alaska Region, and State and Private Forestry (Alaska Region) will cooperate in probe* planning and implementation. Scientists from the following PNW Station programs will form an interdisciplinary team to condu* this research: Resource Management and Productivity, Aquatic and Land Interactions, Social and Economic Values, and Managing Natural Disturbance. This team will work closely with their NFS counterparts at the Regional, Area, and Ranger Districts levels to plan and implement studies. University cooperators include Oregon State University, University of Montana, and Humboldt State University.

Questions frequently asked about Alternatives to Clearcutting

Home | What We Do