Western Juniper Harvest Systems Comparisons Project

by Larry Swan, USDA Forest Service, Winema National Forest
from the Western Juniper Newsletter, Vol. 2, No. 2, Winter 1998.

One of the biggest barriers to commercial use of western juniper is harvest costs. Among factors contributing to high costs are numerous and large limbs, significantly less volume per acre than current commercial species, rocky terrain, and primitive road systems.

The purpose of the Western Juniper Harvest Systems Comparisons Project was to identify and assess harvest systems which already have been tried in western juniper woodlands, what might work which has not been tried, and conduct harvest trials with the best available systems identified. Harvest trial results were evaluated in terms of direct site impacts, production, and production costs.

Harvest trials were conducted on property owned by the Lost River Ranch, Bonanza, Oregon. Total project area was about 15 acres.

The project site was considered "average" for juniper stands with commercial potential: Average tree height was 33.4 feet, average age at stump height was 89 years, and average diameter at breast height was 12.6 inches. Tree density ranged from 25 to 160 per acre. Tree canopy prior to harvest ranged from less than 10% in the least dense area to over 60% in the densest area. Groundcover consisted of a thick carpet of cheat grass.

What's Been Tried and What Might Work?

Seven individuals with commercial western juniper harvest experience, as well as a university harvest systems researcher, were interviewed to determine what has been tried, what worked, what did not work, and what has not been tried that might work. Based on their input, 10 different options involving all phases of a juniper harvest operation were considered for field trials. The two options which appeared most promising for reducing harvest costs were pull-through delimbers and forwarders. A forwarder could not be tested due to insufficient volume and equipment availability.

How Were the Harvest Trials Conducted?

The harvest operation was broken-down into phases and data gathered on each phase: 1) Limbing prior to falling (a technique used in juniper to reduce cost and risk to fallers); 2) Falling with chainsaws; 3) Delimbing with chainsaws; 4) Mechanical delimbing; and 5) Skidding. Three different pull-through delimbers were examined in the mechanical delimbing phase. A rubber-tired skidder equipped with a grapple was used for all skidding.

Two variables were used to evaluate direct site impacts of the harvest systems investigated - soil bulk density change and ability to distribute slash (limbs and other logging debris) evenly about the site. Soil bulk density is an indicator of soil compaction, while slash is often used to provide shade for seedlings, reduce soil temperature variation, reduce grazing pressure on seedlings, add organic matter and nutrients to top soil, and reduce risk of soil erosion. A third variable, success of grass seeding, could not be evaluated due to project and report timelines.

A total of 398 trees were removed, which represented roughly two-thirds of the total standing before harvest (average 82 trees/acre pre-harvest and 27 trees/acre post-harvest).

Results

There was no significant production difference between a harvest system which used chainsaws to delimb juniper and a system which used a pull-through delimber, based on the data gathered the week of the field trials. Both systems averaged about 1.7 tons of juniper per hour at an estimated cost of $27-$29 per green ton.

Performance of the three pull-through delimbers used in these trials differed substantially. The skidder pull-through delimber was least effective with juniper. Limb size and length hindered proper loading and actuation of the hydraulic knives.

There were various reasons why one shovel pull-through delimber performed better with juniper than the other. These included: 1) Larger, heavier, and taller platform; 2) Longer knives; and 3) Self-centering head. All three pull-through delimbers appeared suitable and capable of delimbing trees with smaller limb diameters and lengths.

There was very little difference in bulk densities before and after harvest operations, even though post-harvest sampling was biased towards high impact areas, such as landings and skid trails. Surface organic matter actually increased due to needles shed during whole tree skidding and redistribution of mechanically-delimbed slash from a central landing.

Slash was better distributed in the area that was delimbed with chainsaws (average cover 65%) than those areas where trees were whole-tree skidded to a central landing, mechanically-delimbed, and slash redistributed back out into the unit (average cover less than 15%).

Interpretation and Implications

Harvest Costs - Western juniper harvest is currently expensive, but there are indications that costs will decrease as companies gain experience and try different approaches. For example, according to the logging contractor for the project, production with the pull-through delimber has increased 40% since it was tried for the first time during the harvest trials. Other potential improvements are expected to bring down costs to between $15-$20 per green ton. Although still not competitive with common commercial species, such progress is significant (potential 30% drop in costs within 12 months).

Slash Dispersal - The ability to evenly disperse juniper slash is critical to meet the goal of improving rangeland habitat through commercial harvest. This is difficult to effectively and economically accomplish with a rubber-tired skidder and grapple. Several methods were tried to improve slash dispersion, none of which worked well.

Options to improve slash dispersal were discussed with various government personnel and private industry. Analysis suggests that more limbs can be left on-site without major modification of systems already in use, or a significant negative impact on costs and production.

Mechanical Harvest Impacts on Soils - Some concern has been expressed about the impacts of mechanical harvest on soil types found in western juniper woodlands. Based on the results of this project, minimal impacts are expected on dry clay loam and clay soils. These soil conditions are encountered most frequently in the late summer and early fall, when soil moisture is historically at a minimum.

Harvest Equipment Specifically Designed for Juniper - A number of individuals from private industry believe harvest equipment can be specifically designed for juniper and fabricated for costs approximating the capital investment needed for a used shovel/new pull-through delimber set-up ($75-$80,000). Such equipment would have to reduce harvest costs, improve personal safety, and improve slash dispersal. Efforts are underway by the Western Juniper Commercialization Steering Committee to find funding to sponsor a competitive process to design and field test two prototypes.

For More Information: Larry Swan, USDA Forest Service, Winema National Forest (541) 883-6714.

The full report is available on-line at http://juniper.orst.edu/hvst.htm