MISSOULA – A new study authored by the University of Montana’s Bureau of Business and Economic Research and the U.S. Forest Service Rocky Mountain Research Station examines the impact of the mountain pine beetle on costs, operations and timber product value related to harvesting, processing, transporting and sawmilling trees killed by the beetle in Montana.

The study authors are BBER’s Dan Loeffler and the research station’s Nate Anderson.

Over the past 15 years, the mountain pine beetle has caused considerable pine tree mortality across Montana, affecting more than 9 million acres of forest. The beetles are widely acknowledged as having negative impacts on wood supply by reducing log quality and recoverable volume, as well as negatively impacting operability in the forest and at the sawmill.

Loeffler and Anderson found that trees in the red or gray stage of mountain pine beetle mortality comprised about one-quarter of Montana sawmill log supply from 2010 to 2014, but dropped to 5.8 percent of sawmill log supply by 2015. Sawmills reported that the majority of their log supply was not composed of trees killed by the mountain pine beetle, but many did process trees in the red or gray stage of mountain pine beetle mortality.

The authors found that for a typical lodgepole pine stand, the volume suitable for lumber declined 15 percent between the green and red stages and declined another 50 percent between the red and gray stages. Cracking in the logs, occurring mostly in the red stage of mortality, has the highest negative impact on log value. Increased mill residue and log breakage during handling impacted sawmilling operations.

Loeffler and Anderson also found that logging, loading, hauling and sawmilling costs increase 15 to 18 percent from green to red stage, and an additional 28 to 31 percent from the red to gray stage. Total average cost increases from green to gray for logging, loading, hauling, and sawmilling were 43 to 46 percent.

Because of the low moisture and sap content in standing dead wood, saws and chippers do not perform as well when working with green timber. Logs from beetle-killed trees result in lower-grade lumber and the byproduct, wood chips from milling, also may be less desirable due to the blue stain fungus carried by the beetles. Dust control was cited as a problem in sawmilling as well.

Loeffler and Anderson conclude that increased costs and lower recovery of valuable grades of lumber combine to make beetle-killed timber less economical the longer the trees remain unharvested. They found if a stand is determined to be economically and environmentally suitable for salvage harvesting, there is substantial financial risk in delaying harvesting.


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