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Abstract

Economics and environmental effects of fuel reduction at Limber Jim [ Tech Note No. 10 (PDF, 585k) ]

by J. McIver

Cooperating Scientists:

• James Doyal, Mark Taratoot, Paul Adams, Loren Kellogg (OSU)
• Eric Drews, Bruce Hartsough (UC Davis)
• Roger Ottmar, Bob Vihnanek (PNW Station)

Cooperating Managers (La Grande Ranger District):

• Thomas Burry: Project Coordination, Timber Sale Administrator
• Annette Pepin, James Barrett: Silviculture
• Thomas Wordell, Tracy Kissire, Brenda Younker: Fuel Surveys
• Gabbi Bosch: Traversing
• Bob Rainville: District Ranger

Contractor:

• Andy Munsey (Masonite Corp.)

Fuel reduction by mechanical thinning and removal was studied in mixed-conifer stands on Limber Jim Ridge, La Grande District, Wallowa-Whitman National Forest, between 1995 and 1997. Mixed-conifer stands on this ridge had some of the highest fuel loads on La Grande District, up to 80 tons per acre. A single-grip harvester was coupled with either a skyline yarder or a forwarder, and fuel reduction, soil disturbance, and operational economics were measured in three replicate stands.

The two retrieval systems achieved nearly identical patterns of fuel and standing stem reduction, with 53% of fuel and 36% of stems left after harvest in all units. In forwarder units, more total material was removed per acre compared to skyline units (57.1 tons v. 48.1 tons), though this difference was not statistically significant. About 80% of the total material removed was dead. The only difference in pattern of fuel reduction was for the 9.1-20" size class, where skyline retrieval left 45% of pre-treatment fuel, compared to 74% for the forwarder.

Soil disturbance was statistically identical for the two retrieval systems, with 6.0% area disturbed for the forwarder, and 7.3% for the skyline yarder; both retrieval methods were well within the 15% Region 6 standard, assuming 5% disturbance for existing roads. However, the pattern of soil disturbance was different for the two systems, with the forwarder causing signficantly more compaction than the skyline yarder (1.7% v. 0.2%; P=0.03); there was a trend toward less displacement with the use of the forwarder (4.3% v. 7.0%; P=0.13).

Overall, the entire project was a narrow economic success, at just over $10/ton profit. Revenue in skyline units was slightly higher than forwarder units ($63/ton v. $61/ton); this difference was due to the slightly greater harvest of sawlog material in the skyline units. However, operational cost was $71/ton in the skyline units, and $42/ton in the fowarder units. This difference resulted in a net revenue loss of $10/ton in the skyline units, and in a net revenue gain of $19/ton in the forwarder units. Relatively flat ground and small-diameter/low-value material clearly favored the fowarding machine at Limber Jim; a larger average stem size and greater slope deflection would likely favor the skyline system. These results are discussed in the context of adaptive management, in which operational experiments provide information that allows the manager to assess economic/ environmental tradeoffs inherent in management decisions.