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Pacific Northwest Research Station
Integrating science and experience into silvicultural prescriptions and forest research
Summary of June 14-15, 2007, workshop
Rachel White, Science Writer
The Central Cascades Adaptive Management Partnership, which includes the Eugene Bureau of Land Management, Willamette National Forest, PNW Research Station, Oregon State University, and the H.J. Andrews Experimental Forest, has a history of bringing together researchers, communities, and resource managers to improve the development and transfer of forestry knowledge. This partnership between science and management concentrates on identifying knowledge gaps where science could help solve management problems, leading to our ultimate goal of creating science that is relevant to the needs of on-the-ground practitioners.
With this intention in mind, we convened a workshop in mid-June 2007 to explore current and emerging issues related to silviculturethe basic foundation of many types of forestry management activities. Today, devising silvicultural prescriptions in the larger context of multiple land uses and reduction of wildfire risk creates a difficult decision space for land managersa situation made even more difficult when high-quality science is not available. Furthermore, finding ways to accomplish silvicultural goals that are financially viable as well as socially acceptable is crucial, because even the most scientifically advanced management plan is useless if we cannot implement it.
The purpose of our workshop then, was for managers to bring discussions of current issues in silviculture to the scientists who might be able to inform them through existing studies, models, and management tools, or through future research. The 2-day workshop was deliberately structured to be practitioner-led, with scientists as the audience, so that the scientists could listen to the problems faced by those in the field. On day one, six silviculturists presented their prescriptions, highlighting the constraints they were under, the assumptions they used, the science that guided them, and any tools that helped them succeed. This allowed practitioners to share ideas with each other, and gave scientists a chance to consider how their work could meet the needs of those in the field. Each presentation was followed by a facilitated discussion with the audience of questions raised. Day two provided a chance to reflect on each project through more indepth discussion. For each project, a researcher and a senior silviculturist were assigned to lead a conversation with the group about possible sources of information and tools, current knowledge gaps, and potential roles for practitioners and researchers in developing a base of knowledge and tools to meet local or regional needs. The goal of the second day was to produce a list of researchable questions that would help fill current information needs.
Summaries of the six presented prescriptions
1. Cat Creek Thinning (Gifford Pinchot National Forest, Cowlitz Ranger District), presented by Andrew Larson from University of Washington, and Derek Churchill of Conservation Northwest (Click on the slideshow title to view this presentation in PDF format.)
This 45-acre prescription, originating from a local stewardship group called the Pinchot Partners, was designed as a demonstration stewardship project. The goal was to accelerate late-successional conditions (large trees with complex crowns, decadence, a diverse plant community, multiple canopy layers, and horizontal heterogeneity). The site was in the western hemlock/Oregon grape plant association with moderate site productivity. It had been clearcut in 1957 and then broadcast burned and planted. Pretreatment conditions were Douglas-fir dominated, with lots of big coarse wood, quite a few legacies, residual cedars, and root rot beginning to create gapsoverall, a pretty diverse stand. The design focused on increasing crown class differentiation, accelerating growth and establishment of advanced regeneration and understory, and preventing loss of species and structural diversity.
The prescription was to thin proportionally from the middle, taking mostly Douglas-fir. They did not take anything larger than 15 inches d.b.h. (diameter at breast height, 4.5 feet above the ground); up to 25 percent of the "small stuff" was left. They put in skips and gaps around biodiversity hotspots, and also included additional skips and gaps that were approved by the sale administrator. To retain existing heterogeneity, they removed 50 percent of the trees between 7 and 15 inches d.b.h. in a proportional thinning. They used the following pairing method to select trees: within each pair, they chose the one that was not a wildlife tree, or they chose the smaller tree. Since modeling variable-density thinning is difficult, they went with averages (and used good stand data).
This was an "unusual" and complex contract, which could not be done through the standard Forest Service contracting process. The contract did not sell the first time they put it up for bid. After the cover letter was improved to make it clearer, it sold.
2. Curran Junetta Thinning (Umpqua National Forest, Cottage Grove Ranger District), presented by Suzanne Schindler, District Silviculturist (Click on the slideshow title to view this presentation in PDF format.)
This project included 21 units in a planning area of 7,000 acres. All were 50-year-old managed stands that had been clearcut in the 1950s. The objective was to reduce tree density in second-growth timber (to reduce fire risk). The prescription was for commercial thinning of 1,236 acres using helicopter, ground-based, and skyline logging. Gaps were located based on the following criteria: ¼-acre gaps were dispersed in 11 of the units, and ½-acre gaps were dispersed in 4 of the units. These ½-acre gaps were also located at the limits of access where skyline yarding was prescribed. The silviculturist reviewed marking guides, and used designation by description (DxD) with the presale crew prior to marking.
3. Late-Successional Reserve (LSR) Thinning (Eugene Bureau of Land Management), presented by Rich Kelly, Silviculturist (Click on the slideshow title to view this presentation in PDF format.)
This prescription was developed for a planning area of 24,400 acres consisting of 20- to 30-year-old stands that were not commercial, but in need of thinning. The objectives were to reduce density and develop snags and coarse woody debris. As this project was concerned with young stands, it did not rely on traditional silvicultural practices. The idea was to increase variability of tree spacing in 75 percent of stands, so tree densities would range from 40 to 110 trees per acre within 10 years. The actions taken were: thin approximately 1/3 of the stands to an average residual density of 40 to 60 Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) trees per acre, thin approximately 1/3 of the stands to an average of 60 to 80 Douglas-fir trees per acre, and thin approximately 1/3 of the stands to an average of 80 to 110 Douglas-fir trees per acre. This was implemented using tree girdling to achieve a variable-width spacing for the Douglas-fir. They did not take larger trees (over 16 inches d.b.h.), or trees less than 6 inches d.b.h. They did not girdle species other than Douglas-fir, trees with green limbs to the ground, trees that were leaning, or trees with broken tops. In 1 to 2 years, the girdled trees will die and will break and fall in 5 to 10 years. This type of nontraditional approach can be controversial, and did raise some questions, such as "What differentiates commercial from noncommercial? Are single entries better than multiple entries? How can we create coarse woody debris, and what type of longevity will it have?"
4. The Nature Conservancy (TNC) Project (Ellsworth Forest Preserve and Willapa Bay National Wildlife Refuge, Washington), presented by Bill Lecture, TNC (Click on the slideshow title to view this presentation in PDF format.)
This project involves large-scale forest restoration in the coastal Sitka spruce forest zone. The 7,400-acre Ellsworth Creek drainage was managed primarily as an industrial forest prior to being purchased by TNC. The goal is to put the Ellsworth Creek Preserve on a developmental pathway toward late-successional forest. One major concern is to help the forest develop wind resistance. Other desired conditions include ecosystem resilience, spatial and temporal variability, functional landscape linkages, and habitat for late-successional forest species. With wind being the dominant disturbance factor, the recommendation was to thin lightly and frequently. Six thousand acres of the Ellsworth Creek Preserve are available for active management after setting aside ecological reserves, limited-entry buffers, marbled murrelet (Brachyramphus marmoratus) habitat, and riparian buffers. Current challenges include: cost effectiveness, differing objectives among landowners, considerations of climate change, and finding a way to incorporate natural processes into restoration. To improve resiliency, they are encouraging Douglas-fir. They have found there is nothing they can do to keep hemlock (Tsuga spp.) out.
5. Railsiding Thinning (Sol Duc Valley, Olympia National Forest), presented by Verne Farrell, Silviculturist (Click on the slideshow title to view this presentation in PDF format.)
In this project, the goals were to develop terrestrial habitat, to demonstrate management of hemlock (Tsuga spp.) "carpets," to allow retention of full crowns and encourage diameter, to open up the understory and reintroduce herbs and shrubs, and to develop a stand with three canopy layers. The pretreatment stand condition was a variable understory, with 5,000 to 20,000 trees per acre. The prescription was to thin to an average spacing of 16 feet, from below. The assumptions were that once hemlock is established it can be thinned mechanically, that two canopy layers plus an understory would be able to prevent a second pulse of hemlock, that thinned understory hemlock would be able to thrive without lots of "wet noodling," and that herbs and shrubs would be able to flourish in thins. The area was thinned in two stages, first in 2001, then in 2004. Potential problems included the contractors not understanding the prescription (inadvertently cutting shrubs, etc.), slash, and wet noodling. Overall results of the treatment were the elimination of the hemlock carpet, a few midstory hemlocks and vine maples (Acer circinatium Pursh), a few wet noodles, no pulse of hemlock regeneration, and much more ground vegetation.
6. 700 Road Thinning (Cedar River Municipal Watershed, Washington), presented by Rolf Gersonde, Seattle Public Utilities (Click on the slideshow title to view this presentation in PDF format.)
The Cedar River watershed is part of the water supply for the city of Seattle, and also includes habitat for threatened salmon. Important objectives for this prescription therefore included safe and secure drinking water, and conservation of important fish habitat. Pretreatment forest was a 65-year-old cohort of western hemlock (Tsuga heterophylla (Raf.) Sarg.), with densities of 200 to 400 square feet of basal area per acre. The project was designed with stakeholder involvement, including local tribes, conservation groups, oversight committees for the watershed, and local citizens. After a public involvement workshop, the project took a year to design. Public comments pushed for yarding fewer trees, creating more gaps, thinning conservatively, and not cutting big trees. In the end, 230 acres were thinned. Yarding corridors created gaps, and smaller skips and gaps were located by the operators. Operator certification was done beforehand to ensure that operators could "read the fine print," and fully understood the prescription. Only one successful bidder could implement downhill yarding. The project designers used a light model to create variability, and the Topex model to calculate topographic exposure and effect of tree position relative to gap edges on diameter growth and average crown width. They found that creating gaps had a greater effect on creating large trees than thinning.
US Forest Service - Pacific Northwest Research Station