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CORVALLIS - A study by forestry researchers at Oregon State University has confirmed that careless harvesting of American matsutake mushrooms, a significant private enterprise on public lands in the central Oregon Cascade Range, can reduce subsequent harvests by up to 90 percent.

This devastating impact on the sustainability of this valuable forest crop can be avoided by use of "best management" practices recommended by forest management agencies, in which hand picking, sometimes aided by a small prying tool, is used to carefully pop single mushrooms out of the ground with minimal disturbance of nearby soils.

Proper awareness and use of these techniques can be invaluable in protecting a cottage industry that in peak years has yielded millions of dollars in mushroom crops, hundreds of thousands of dollars in permit fees and considerable income for local merchants, said Dan Luoma, an OSU assistant professor of forest science and one of the nation's leading experts on mushroom ecology.

"This study clearly confirms that regulations to control the way in which matsutake mushrooms are harvested are essential to maintaining the long-term health of the resource," Luoma said. "What we have found so far is that use of the best possible harvesting techniques has the same impact on future numbers of mushrooms as no harvesting at all. Only long-term monitoring will determine if that trend can be expected to continue."

The primary concern, Luoma said, has been pickers who deeply rake the soil to uncover the matsutakes, which often lie barely beneath the ground's surface at their young, and most valuable stage of development. But the mushroom itself is only the fruit of an underground fungal colony, and disturbing the roots and spread of that colony may interfere with its growth in later years.

In a site near Diamond Lake, Ore., OSU scientists, Forest Service personnel and other volunteers studied the effect of a deep raking, in which soil and other tailings were left scattered about; a shallow, more careful raking in which tailings were carefully replaced; the use of best management practices to harvest individual mushrooms; and no harvest at all. The research, now in its 10th year, aims to enable sound, sustainable management of the matsutake resource.

They found that no harvesting or best management practices caused virtually no drop-off in future harvests.

A single, shallow raking and soil replacement had only a very minor impact. But a shallow rake without tailing replacement caused future mushroom numbers to drop 75 percent, and a single deep raking caused a 90 percent drop in mushroom numbers.

"There may be only a small minority of irresponsible pickers who have done deep raking in the past, but clearly it wouldn't take much of that to cause a real problem," Luoma said. "And from a management perspective, it's very difficult to enforce or monitor any type of soil replacement after raking. The best approach to ensure future harvests for all pickers will be to leave raking out of the harvest altogether."

Luoma teaches workshops on mushroom ecology to forest managers, helping them to understand how these fungi grow, reproduce, are involved in the forest food web, and can be sustainably managed.

"Actually, the last few years for matsutake harvests have been fairly poor in Oregon, nothing like the banner year we had in 1997," Luoma said. "These mushrooms like a drier spring and more moisture in late summer or early fall, which we don't often get."

The matsutake is prized as a delicacy in Japan, where almost all of the Pacific Northwest harvest ends up. In Oregon, the dry, sandy soils of the Winema and Deschutes National Forest are the hub of matsutake harvests and one of the world's key harvesting regions, by some estimates accounting for 8 percent or more of the world supply. The region in some years has attracted 1,500 or more pickers who seek this prized species that can bring $6 to $30 a pound, depending on quality and market forces.

The matsutake harvesting season begins in late summer and ends in November, and is often driven by nomadic hunters who follow the season south from British Columbia to California, trying to spot the hidden matsutake at the base of pine trees by a puffy rise in the soil and needles.

The discovery of the value of this mushroom harvest in the 1990s in Oregon has clearly had economic impacts on the region, and last year 1,873 permits were sold at a value of $171,000. The market value of the harvested mushrooms varies wildly, but is probably in the millions every year, and has become one staple of the "special" forest products that are helping to provide value from Pacific Northwest forests during a time of dwindling timber harvests.

Matsutake mushrooms have been used by the Japanese for more than a millennium and represent even more than a delicacy food item - they are also a symbol of fertility, good fortune and happiness, OSU experts say. The importation of American matsutakes has soared while harvests of a similar species in Japan have dropped dramatically, partly as a result of insect infestations that have taken a toll on pine forests in Japan.