CORVALLIS - The near disappearance of old growth timber harvests in the Pacific Northwest has caused resurging interest in a lost art - pruning.
With the demand for clear, blemish-free wood near an all-time high just as the supply of this wood dries up, Oregon State University forestry Extension specialists say that everyone from timber companies to the small woodland owner is reconsidering the merits of pruning to improve log quality.
It now appears that pruning may not only be cost effective, the researchers said, but can create new jobs while improving the appearance, health, fire resistance and vegetative diversity of the forest.
"The end result," said Rick Fletcher, a Benton County forestry Extension agent, "may be that timber workers who used to head into the woods with a chain saw will now take along a ladder and pruning shears."
The Japanese have paid almost five times as much for clear, old growth Douglas-fir as for a 50-year-old, non-pruned tree, Fletcher said.
"There's a huge premium for clear wood and there just is not much of it available anymore," he said. "The pruning trend is real and will grow."
Older forests "self-prune" themselves as their lower limbs decay and fall off, producing significant amounts of clear wood by about 120 years of age. But the dramatic decline of old-growth harvesting and move toward younger second-growth rotations has forced a situation where humans must intervene if they want clear lumber, Fletcher said.
One recent cost-benefit analysis has shown that pruning now has a higher economic payback than fertilization or thinning.
Other benefits include:
- Pruning can decrease fire danger by removing "fuel ladders"
- Access to dense stands and overall appearance can be improved
-Thinning and pruning combined can bring more light to the forest understory, enhancing vegetation which benefits wildlife and livestock
- Pruning may lessen the impact of some plant pathogens and infections
To re-discover the value and techniques of pruning, Fletcher said, he and other OSU scientists have been exchanging information with scientists in New Zealand, where pruning of fast-growing radiata pine has been done for decades and developed into a near art form.
"They've tried practically every type of pruning in New Zealand and know all about when to prune, how, and with what equipment," Fletcher said. "They've used everything from saws to hand loppers and a robotic pruner that spirals around the tree while it climbs and prunes limbs."
A favored system in New Zealand involves a specially designed hand-powered lopping shear and several fixed height ladders. Use of a "pneumatic pruner" that works from an air compressor also shows considerable promise.
Commercial forestry pruning must be done properly, Fletcher said.
At the wrong time of year it can invite insect attack. Cutting off too many live limbs at once can slow tree growth, but also has the most potential impact to improve wood quality, so an optimal balance must be sought. Exposing thin bark on juvenile tress can lead to sun scalding and tree scarring.
Pruning is catching on quickly with smaller private landowners, Fletcher said, who see it as a fulfilling job they can do at their convenience and with little cost. Some major forest product companies, such as Weyerhauser, are also committed to pruning significant acreage, he said.
"Not all of the large industries are yet convinced about the payoff," Fletcher said. "At about $8 a tree and pruning 100 trees per acre, that's a major investment of $800 per acre when the payoff could be 30-40 years away."
Forestry investments of that caliber, he said, also call for a stable business climate that's not prevalent at the moment, he said.
But despite the costs and concerns, pruning is a growing industry, Fletcher said, and shows signs of expanding. Pruning crews that didn't exist five years ago are now working in Oregon forests.
The need to learn more about the fine points of tree pruning, Fletcher said, attracted an overflow crowd to an OSU College of Forestry pruning conference last fall.
A new Extension workbook on the topic was also just completed, titled "Pruning to Enhance Tree and Stand Value." It can be obtained for $1.50 by writing Publications Orders, OSU Extension and Experiment Station Communications, 422 Administrative Services, Corvallis, OR 97331-2119; or by calling (541) 737-2513.