Health of Forests May Depend on Fate of Fungi

Joyce Eberhart knelt on the forest floor, using a short-handled rake to probe the damp decomposing twigs, leaves and needles for living hidden treasures--truffles and mushrooms.

“Found one!” the Oregon State University research assistant said, holding it up for Forest Service soil scientist Mike Amaranthus to see.

” Rhizopogan parsii ,” he said, reciting the truffle’s genus and species.

Eberhart put it in a paper sample bag and logged its location, entering another piece of data in the start of a 200-year study to map the secrets of the forest that lie underground.

“I feel like the people who designed the cathedrals and never saw them actually built,” Amaranthus said. “We want to have some good base-line data so someone else can make good evaluations in the future.”

Mycologists have known for 100 years and foresters for perhaps 30 years that fungi that produce the mushrooms and truffles known as mycorrhizae have evolved a partnership with trees without which neither can live.

Meanwhile, high prices for wild mushrooms have drawn crowds of commercial pickers into the Northwest woods for a harvest reported at $60 million last year in Oregon alone by the state Department of Agriculture.

That leaves people like Amaranthus wondering whether the mushroom rush ultimately could threaten the entire forest, where mushrooms and truffles make it possible for trees to weather drought and draw nutrients from the soil.

“There is no good information,” Amaranthus said. “The only thing we have is the European experience, which is a severe decline in the population of wild edible mushrooms.”

To find out, he has researchers mapping fungi in forest sites from Alaska to southern Oregon, which will be visited periodically to see how they fare after logging and fire. It is part of an effort to gain a deeper understanding of how the forest as a whole works.

“It seems like all this should have been done before, it’s so fundamental,” Amaranthus lamented.

In 35 years of studying mushrooms, Jim Trappe, professor of forest science at Oregon State University, has never enjoyed abundant funding.

And so little work has been done on truffles, which fruit underneath the duff on the forest floor, that new species are popping up all the time. The North American Truffling Society in Corvallis has at least 50 species in its herbarium waiting to be described and named.

“I think we are talking about many, many hundreds of species yet to be discovered,” Trappe said.

What is known is that 95% of all plant life depends on mycorrhizal fungi to draw water and nutrients from the soil. The fungi attach to the roots of a Douglas fir, for example, and spread their long hair-like hyphae throughout the soil. There, they link up with other trees, rain-soaked logs and even rocks to pump water and nutrients to the host. In return, the fungi draw sugars from the tree.

“The great evolutionary leap of plants was due to this,” Amaranthus said. “It allowed them to colonize a great hostile environment.”

Amaranthus collects truffles and uses the billions of spores in each one to inoculate tree seedlings in nurseries, giving them a head start on life in the woods.

The relationship is complex. Trees draw on different fungi in the various seasons of the year and at progressive stages of their lives. A single thimbleful of soil can contain miles of fungal filaments. After a forest is clear-cut, the fungi die out within several months.

What is not known is what happens after many years of pickers armed with rakes and leaf blowers scour the woods for mushrooms, particularly the matsutake, or pine mushroom.

A prime specimen can bring $100 in Japan, where they are revered. Good pickers can earn hundreds of dollars a day. The Crescent Ranger District on the Deschutes National Forest reported $15 million worth of matsutake exports in 1989.

The boom started about 10 years ago, corresponding with the decline in wild mushrooms in the forests of Europe.

“Acid rain, other forms of air pollution, replacement of the native mixed hardwood-pine forests with Norway spruce, shortened rotations, repeated logging--all these may be involved” in the European decline, Trappe said. “In Japan, the same things have been going on.”

Members of the Oregon Mycological Society often talk of returning to a favorite hunting ground, only to find it picked clean. Prime spots are kept secret, like favorite fishing holes.

Is this just like plucking an apple off a tree, doing no harm to the tree? Or can intense raking and digging to discover the most valuable mushrooms, which have not yet popped out of the ground, permanently damage the fungi, threatening the health of the trees as well?

No one knows for sure.

Lorelie Norvell, a graduate student in mycology at the University of Washington, started studying the issue three years ago with plots of chanterelles.

Two years of data seem to suggest that chanterelle production may actually benefit slightly from picking. Evidence from Europe seems to suggest that mycorrhizal mushrooms, those that attach to plants, also may benefit.

But Norvell would like to know what happens after 25 or 30 years. She also wonders whether removing so many mushrooms, and not allowing them to drop their spores on the ground, may affect the survival of the fungi.

Trappe says most pickers would act responsibly if someone could tell them what was best for the mushrooms.

“But all we can do is guess,” he said.