he lush coastal rain forests of the temperate climate zones rank among the rarest and richest forests on earth. Although remnants survive along the west coasts of Norway, Chile, Tasmania, and New Zealand's South Island, more than half of the world's remaining temperate rain forests stretch along the Pacific coast of North America from southeast Alaska down through British Columbia, Washington, and Oregon to northern California.1 Cathedral groves of centuries-old Douglas firs still soar 15-30 stories high in places, creating damp twilight worlds where layers of cedar and hemlock, mosses and lichens, shrubs and spongy rotting logs succor mushrooms, salamanders, squirrels, birds, and bears.
Foresters who focused solely on timber production once pronounced such ancient conifer forests "over-mature," in need of cutting and rejuvenation. By the time ecologists began to challenge that view and reveal the vitality and complexity of old-growth forests, it was becoming apparent that these giants were being cut faster than anyone had realized. Nearly 90 percent of the temperate rain forests had been felled by 1990, reflecting a deforestation rate far greater than that in the better publicized and more extensive rain forests of the tropics.2 A variety of economic, social, and scientific factors were converging, however, to bring a halt to rampant logging of Pacific Northwest old growth, from the needs of the endangered northern spotted owl to public protests and international boycotts of British Columbia timber.3 Many public agency and corporate timber managers have now committed to reducing the cut and embracing a kinder, gentler ecosystem-based approach to logging called "new forestry."4 This new approach recognizes, among other things, the need to protect forest soil communities, especially the vast underground web of mycorrhizal fungi that serves as an indispensable lifeline between forests past and future.
To the uninitiated, site C1500 on the east side of Vancouver Island looks no kinder or gentler than thousands of other clearcuts pocking the region. C1500 lies only 30 miles northwest of downtown Victoria, the capital of British Columbia, yet it takes nearly 2 hours for forestry technician Bob Ferris to negotiate a roundabout maze of rugged logging roads and pull his truck to a halt at this site in the Koksilah River valley. I climb out of the truck with Canadian Forest Service soil ecology research scientist Tony Trofymow and biologist Renata Outerbridge into a cold late October wind at the edge of a cutover hillside. This 160-acre site—about 1/4-mile square—is one of a half dozen on southern Vancouver Island that the Canadian Forest Service researchers have been studying to see how mycorrhizal fungi are faring under a partial-harvesting practice called "variable retention." This site had been blanketed by old-growth Douglas firs until 1999 when it was harvested by the timber company that owned it, MacMillan-Bloedel Ltd. That was the year after the company had pledged to phase out clearcutting in favor of variable retention. That commitment was later taken up by Weyerhaeuser's Coastal British Columbia Group, which took over MacMillan-Bloedel in late 1999 to become Canada's largest timber company. As we walk to the edge of the clearing, Trofymow begins to point out why, aesthetics aside, what we're looking at is not a classic clearcut.
One clue is a remnant patch of old growth rising from a rocky outcrop just upslope from the truck. The key to the new forestry, it turns out, is not just what's been taken away but also what remains. In variable retention, loggers cut at a range of intensities across a forested landscape, sparing patches or individual trees. On this site, Trofymow tells me, the crews left behind blocks of trees amounting to 15 percent (24 acres) of the original forest. Green trees are only the beginning, however. In the jargon of new forestry, what should remain amid the forest patches is a messy clearcut full of complex "biological legacies" from the old forest to help "lifeboat" the creatures, habitats, and processes that will enhance the recovery of tomorrow's forest. Legacies aboveground include not only live trees but also standing dead ones, downed logs, limbs, and shrubs. Equally vital are the legacies underground: roots, seeds, complex soil communities, and stocks of nutrients and organic matter.5 I'm reminded of the "legacy carbon" that helps sustain life in the soils of the Antarctic Dry Valleys between wet seasons.
The legacies that foresters call "structure" are hard to miss as we walk upslope toward the patch of ancient trees above us, clambering over downed logs and other woody debris and pushing through low, dense salal shrubs, wild rose, and the serrated, pants-grabbing leaves of Oregon grape. The glossy oval leaves of salal are popular in flower arrangements, and Vancouver Island has become a prime area for pickers who sell salal branches to the florist trade. In the past, logging crews would have sprayed weed-killer on the salal and other shrubs and wildflowers to reduce competition with the replanted fir seedlings that dot the clearing below. Similarly, loggers once would have removed the slash or woody debris by burning the entire site. That practice has been abandoned here as much because of smoke and air-quality regulations as the need to retain downed wood and avoid scorching the thin forest floors on many of these slopes, Trofymow says.
Continuing upward, we enter a remnant stand dominated by tall, straight Douglas firs, their lowest branches well beyond our reach, and a few stately western hemlocks topped by droopy spires. The un-derstory is sparse here, the rocky ground covered thinly with soil and expanses of reindeer moss. Despite its name, reindeer moss is actually lichen, Outerbridge points out, a symbiotic pairing of fungi and algae.
The trunks of the ancient firs around us are festooned with many other types of lichens as well as true mosses and liverworts, all denizens of the cool, damp forest interior. Will they survive here and help to recolonize the future forest despite the drying winds and sunlight that now intrude at the cut edges of this stand? New forestry is still as much art as science, and questions about how to monitor success are what have brought us to this site.
Outerbridge brings me a stick with bird's nest fungus growing on it, one of the same fungi I saw in the Smokies. A saprotroph—an organism that feeds on dead and decaying matter—this fungus absorbs its nourishment from decaying wood. She pokes around in the duff and holds up a small, thin-stalked Mycena mushroom, the fruiting body of one of the most common wood and litter decay fungi in this forest. Literally thousands of fungal species help to run these temperate rain forests by breaking down and decomposing wood and other recalcitrant debris, influencing community structure by attacking trees, or forming mutually beneficial partnerships as lichens, my-corrhizae, or endophytes. Endophytes make their homes unseen inside plant tissues and sometimes help protect their hosts from insects or disease. The Douglas firs all around us, for instance, harbor tiny fungal endophytes within their needles that produce chemicals noxious or toxic to grazing insects. And fungi also play vital roles in forest food webs. Many small rodents such as squirrels and voles eagerly consume truffles and other underground fruiting bodies, later depositing feces loaded with fungal spores and unwittingly helping to spread mycorrhizal fungi.6
It's those buried truffles and large fleshy mushrooms—and more important, the underground cooperative network of mycorrhizae that produce them—that most interest Outerbridge and Trofymow, and Weyerhaeuser as well. These are the fungi I've come to Vancouver Island to learn about. Their aboveground manifestations are one of the most sought-after commodities in these forests. Even now, mushroom buyers are stationed at Cowichan Lake another 20 miles west of here to purchase chanterelles from commercial foragers. These yellow-gold delicacies fetch a higher price per pound on the international market than timber, salal, or other natural goods harvested from the coastal temperate rain forests.7 Outerbridge, who recently earned her doctorate studying the mushroom communities under various types of tree plantations, has a plastic bag of chanterelles, along with a few similarly prized matsutakes or pine mushrooms, sitting in her home refrigerator, the rewards of a weekend foray to Cowichan Lake. Tro-fymow, who earned his stripes as a soil ecologist probing how various assemblages of soil creatures affect decomposition and other processes in grassland soils, began collecting forest mushrooms to eat and taking his children on weekend mushroom-collecting forays years before his research for Canadian Forestry drew his attention to mycor-rhizae. But gathering mushrooms is now merely a savory side benefit to their interest in these fungi.
Chanterelles, matsutakes, morels, porcinis, boletes, and many less tasty mushrooms are the reproductive parts—sporocarps or fruiting bodies—of mycorrhizal fungi—specifically, ectomycorrhizal (EM) fungi. Forest ecologists and managers alike now recognize that without the support of a rich legacy of EM fungi, no new forest would grow on this cutover site.
EM fungi are one of the three most common groups of mycor-rhizal fungi. Their hyphae form a sheath called a "mantle" around a rootlet and deploy a network of silklike threads into the spaces between root cells. Like other mycorrhizal fungi, they project other hyphae far out into the soil, gathering and sharing water and nutrients such as nitrogen and phosphorus with their hosts in exchange for a share of the sugars the plant makes through photosynthesis. EM fungi are the ones that partner with the roots of firs, pines, and other conifers, as well as many other trees. Second among the common groups of mycorrhizal fungi are the arbuscular mycorrhizal (AM) fungi, whose hyphae actually penetrate the root cells of their host plants and do not form mushrooms. This is the most ancient and widespread group of mycorrhizal symbionts, and their hosts include most grasses and wildflowers, many of our most valuable crop plants, most tropical trees, and even the western red cedars of the Pacific Northwest forests. Third are the ericoid mycorrhizae that form on the roots of many forest shrubs such
Chanterelles and other highly prized edible mushrooms are the visible manifestations of vast underground networks of ectomycorrhizal fungi that form sheaths around rootlets and use their microscopic hyphae to extend the nutrient-gathering reach of tree roots. These fungal partners are essential for the growth of Douglas firs.
as salal and rhododendrons. All told, 90 percent of the plants in the world form cooperative partnerships with one or more species of my-corrhizal fungi. Some plant species can take the marriage or leave it, but Douglas firs must have fungal partners to thrive.8
Mycorrhizal fungi are mostly touted for their role in helping plants obtain water and nutrients, but these beasts provide a much wider array of services that helps to shape both the plant community and the soil community. (I say "beasts" with some justification because genetic evidence shows fungi are closer kin to animals than plants.9 Although they appear "rooted" and immobile like plants, fungi don't photosynthesize or make their own food as plants do. And they stiffen their cell walls with chitin, the same material from which arthropods such as lobsters and beetles form their shells [external skeletons].) Mycorrhizae can form a maze of underground links between plants, using this hyphal conduit to share carbon and nutrients among them—for instance, doling out sugars provided by Douglas firs to hemlocks and other species growing in the shade below. Hyphae also exude some of these sugars into the soil, enhancing soil structure by binding particles into aggregates. Microbes feed on the exuded materials and on the hyphae themselves. Some mycorrhizal hyphae secrete enzymes that help decompose organic matter and even "mine" rock for mineral nutrients. Others produce antibiotics that protect plants from pathogens.10
We scramble down to the edge of the remnant old-growth stand where the trunk of a large Douglas fir has been ringed with blue tape and spray painted with an orange "T2." This tree marks the start of one of several transects that Outerbridge and Trofymow have marked, running from the forest edge out into the cut. Every 15 feet along these transects out to 150 feet from the cut edge, they have planted fir seedlings as "bait" to capture EM fungi that persist or are dispersed in the soil at various distances from the edge of the remnant forest. We work our way through the shrubs and debris well out into the clearing. Ferris helps Outerbridge dig up a foot-high fir seedling and bag its roots in clear plastic. We'll have to wait until we get back to the lab in Victoria and examine these roots under a dissecting microscope to learn the abundance and diversity of mycorrhizae that have colonized them.
Trofymow points out that this site was an early effort at variable retention, and it probably would not pass muster with company planners today. Retained patches are supposed to reflect the characteristic structure of the former forest. Yet the trees on the rocky ground above where their transect begins are probably smaller than the ones that grew on the deeper soil of the open hillslope, and thus not representative of the preharvest site. More old-growth patches should have been left standing on the productive soil of the slope, he believes. Neither cutting pattern would be likely to please those who want to see untouched forests here. But for Weyerhaeuser and others who plan to continue cutting trees, the main concern is not how the site looks but whether the patterns and practices applied here will sustain a rich array of forest dwellers, ensuring both the preservation of forest biodiversity and the success of forest recovery. One way to gauge the effectiveness of their practices is to monitor whether cutover sites retain the range of habitats, tree types and ages, and standing dead and downed logs found in old-growth forests. Another is to monitor how key plants and animals—sentinel organisms or bioindicators—respond to various harvest practices. Mycorrhizal fungi are obvious candidates, both because of their value to tomorrow's trees and also as part of the inherent biological diversity of these forests. What's more, my-corrhizae don't fare well in classic clearcuts, especially those stripped of debris and sterilized by fire and herbicides, because these fungi rely on aboveground greenery to supply them with energy.
A day earlier, I had gotten a glimpse of how the mycorrhizae are faring in this and the other Variable Retention Ectomycorrhizae Study (VRES) sites when I joined Trofymow, Outerbridge, and 20 other scientists in Nanaimo, a town 70 miles up the east coast of Vancouver Island from Victoria, for a meeting of Weyerhaeuser's Adaptive Management Working Group.
New forestry owes a great deal to the eruption of Mount St. Helens in 1980. The cataclysm scorched and leveled 230 square miles of for est in southwest Washington, leaving a visual wasteland of charred logs, volcanic rock, and ash covering the mountain slopes. Yet within 3 years, University of Washington ecologist Jerry Franklin and his colleagues were able to locate 90 percent of the plant species from the pre-blast communities surviving somewhere on those messy slopes.11 Not just plants but also small burrowing animals, insects, soil denizens, and other creatures emerged from the destruction and set to work putting the system back on its feet. These findings, combined with several decades of research on the complex ecology of old-growth forests and the impacts of other natural disturbances such as fires and windstorms, convinced Franklin and others of the critical importance of biological legacies in ecosystem recovery.12
This realization, in turn, began to undercut a long-standing rationale that foresters had used to justify clearcutting: that it mimicked wildfires and other natural disasters. Unlike fires or even volcanic blasts, however, clearcuts simplify and homogenize landscapes, sweeping away most legacies, fragmenting the sites with roads, and replacing complex forests with the equivalent of tree farms. At a significant number of high-elevation clearcuts in the Pacific Northwest, in fact, foresters have not been able to get any trees to grow despite repeated plantings.13
It was Franklin who began to pull this information together in the late 1980s and publicize its implications under the catchy and controversial label of "new forestry."14 He declared that timber production must no longer be the driving force in forestry. Instead, forested landscapes should be managed to mimic the complexity of natural forests and supply us not only with wood products but also biodiversity, wildlife habitat, productive fisheries, healthy watersheds, and not least, future forests.
But that is a philosophy, not a prescription. The devil, as usual, is in the details: What fraction of the trees should the chainsaws spare, how far apart, in what pattern, and in what habitats on any given landscape? Weyerhaeuser's Coast Forest Strategy, for instance, now zones its forests into three categories—timber, habitat, and old growth— depending on the values that will be emphasized.15 The zoning determines the intensity of timber cutting allowed on a specific tract, as well as the proportion of the area available for harvest. Virtually all of Weyerhaeuser's privately owned land, such as C1500, is zoned as timberlands. Most of the land zoned for habitat or old growth is "crown" land leased long term from the provincial government. Besides its own decision to manage for nontimber values, the company must abide by a provincial forestry practices code that calls for special protections for streams, wetlands, some old growth, and other sensitive habitats. The result is that at the landscape level, a minimum of 20 percent of the forest in the timber zone, 30 percent in the habitat zone, and 66 percent in the old-growth zone will be retained.
Because new forestry is literally new, and because it can take 60 years or more to regenerate a mature forest—and at least 250 years to get old growth—no one applying these novel practices today will live to see whether they succeed. Thus, Franklin recommends treating each forest management practice as "a working hypothesis whose outcome is not entirely predictable."16 That means employing what ecol-ogists call "adaptive management"—a formal system for learning from the consequences of your actions. Learning requires monitoring consequences, and in this case that means keeping an eye on how sensitive groups of plants and animals are faring in various zones.
During the drive to Nanaimo, Trofymow had described one fundamental working hypothesis of new forestry that bears on the fate of life underground.
"One of the hypotheses used in planning cuts is that you shouldn't leave more than two tree lengths between retained trees or patches," he explained. "That's based on some research involving seed rain and dispersal of tree seeds. But are two tree lengths appropriate for all the other ecological values you're trying to sustain? What if you need no more than one tree length between patches for lichens? Or less than one length for some important soil organism or process? That's what this adaptive management effort and all the research is about. And if monitoring shows important functions and biodiversity aren't being sustained at two tree lengths, the idea is that they'll modify their practices and see if that helps."
But, I wonder aloud, will a timber company really want to change its harvest practices if snails or fungi or even birds don't seem happy?
"That's the $64 million question," Trofymow acknowledged.
One of Weyerhaeuser's stated goals has been to obtain third-party certification for its sustainable forestry practices in coastal British Columbia.17 That seal of approval, in turn, should help it reap any marketplace rewards that come with being a "green" timber company. So in 1999, the company began submitting its plans and practices to annual reviews by an independent panel that has included Franklin and other prominent ecologists as well as representatives of major environmental groups. And Weyerhaeuser began developing what Franklin and others viewed as an innovative adaptive management effort.
The picturesque harbor town of Nanaimo got its start shipping out coal and logs from nearby mines and mills. Although it draws a growing parade of tourists, it still serves as headquarters for Weyer-haeuser's coastal timberlands, forest supply companies, and regional offices for provincial forestry and environment ministries. Many of the scientists attending the adaptive management workshop had spent season after season in the forests and cutover lands of Vancouver Island, listening for songbirds such as Townsend's warblers and golden-crowned kinglets, waylaying red-legged frogs and long-toed salamanders, searching damp places for tightcoil snails and jumping slugs, digging pitfall traps to census predatory carabid or ground beetles, mapping lichens and greenery, and examining tens of thousands of root tips for mycorrhizae. In the darkened room in Nanaimo, however, their findings were projected on screen as data points on charts and graphs, all configured to try to address tricky questions: What does 15 percent or 40 percent retention in patches "look like" to a snail, a bird, a beetle, or a fungus? Do any of them "care"? What does their presence or absence, abundance or diversity tell us about specific timber cutting practices? And what might we expect from them as the new forest grows and matures?18
Glen Dunsworth, then overseeing the adaptive management program for Weyerhaeuser, explained that the goal is to gather enough information on indicator species or groups to develop "species response curves"—that is, a graph that plots each creature's abundance or diversity or some other attribute against tree retention levels. "We want to know, is higher retention always better for a species, or do the returns level out at some point, so that, say, 25 percent doesn't do much more than 20 percent for the abundance of a certain species?" he told me during a lunch break. "And how do species attributes or abundances change as the matrix [the cutover site] ages?"
That afternoon, Outerbridge told the group that she had dug up 264 little fir trees along the VRES experimental transects since 2000. Back in the lab, she had clipped off a measured number of root tips from each fir—more than 40,000 root tips altogether—and examined them for the assorted colors and shapes assumed by ectomycorrhizae. Across all six VRES sites, Outerbridge had found 51 types of EM fungi. The seedlings planted in former old-growth sites such as C1500 had higher levels of root colonization and hosted a greater diversity of EM types than those planted in second-growth forest sites. Perhaps more important, the closer the seedlings were planted to the edge of a remnant forest patch, the greater the diversity of EM fungi on their roots and the higher the percentage of their roots that were colonized. That is what ecologists call a strong "edge effect."19
But the edge the fungi responded to turned out to be farther out into the clearing than the one I see as we pack up the freshly dug seedling at C1500 the day after the Nanaimo meeting. Outerbridge had found that the greatest declines in colonization and diversity actually occurred 50-150 feet out from the visible forest edge.
The key, Trofymow explains as we return to the truck, is that the roots of the old trees are extending out underground at least 16 feet or more into the clearing. It is another of the many unseen legacies that web this site.
"Those old trees we see at the edge of the stand have a root system that would be extending out, and then you have young trees whose roots would come in contact and become colonized with my-corrhizae through root-to-root contact," he explains. "And the roots of the young trees would then extend on and colonize other trees and so on in stepping-stone fashion," forming a vast nurturing network underground.
Some indication of what Trofymow and Outerbridge are likely to find in their research on how EM fungi fare at various levels of tree retention comes from a large-scale study in Washington and Oregon— the Demonstration of Ecosystem Management Options or DEMO project set up by the U.S. Forest Service to test new forestry concepts.20 Oregon State University ecologist Daniel Luoma and his colleagues found that both EM fungal diversity and mushroom production improved dramatically from a clearcut to 15 percent tree retention to 40 percent retention. They were surprised to find in the 15 percent retention sites that mushrooms disappeared from under the retained green trees as well as from the clearing.
"The mycorrhizae were still there, totally intact, in the uncut patches," Luoma told me. "So the organism did not go away, but it stopped reproducing in the patches that were left behind." He speculates this was the result of a sudden change in wind, temperature, or moisture at the patch edges.21 How long does it take for that shock to fade away? Studies like those at VRES and DEMO as yet provide only snapshots taken immediately after a harvest. "The dynamics of the recovery process are really the critical issue," Luoma said.
Trofymow also believes that the critical information is how the fungal community will recover over time: "We saw strong edge effects, but how long do they last? How long before the mycorrhizae colonize these clearings?" One way to get a glimpse of the answer without waiting for decades is to compare how fungi and other creatures are faring in forest sites of different ages. That's what Trofymow and his colleagues in the Canadian Forest Service had in mind in 1992 when they established a project called the Coastal Forest Chronose-quence on Vancouver Island.
Years before timber companies and government agencies began to embrace new forestry techniques, ecologists working in the coastal rain forests of British Columbia had begun to wonder what else was being lost along with the old-growth forests and how long it might take for biodiversity and ecological processes to recover—if ever—in second-growth forests. By 1989, 40 percent of the land on Vancouver Island—including more than half of the mature old growth—had been clearcut and converted to "managed forests" of even-aged firs.22 Within another decade, nearly one-fourth of the virgin forests along the entire British Columbia coast had been logged, creating 7.4 million acres (3 million hectares) of second-growth forest. Trofymow and other researchers have dubbed it, somewhat wryly, "our 3-million-hectare experiment on the coast"—an unfortunate test of what happens when an entire stage of forest development is eliminated.23 The chrono-sequence project was set up to learn from that impromptu experiment.
Researchers picked eight sites on Vancouver Island for intensive study. Within an area no larger than 2 square miles, each site contains forest stands of four distinct ages: regenerating stands that were then 3-8 years old, immature stands 25-45 years old, mature stands 65-85 years old, and old-growth stands greater than 200 years old. For 5 years, teams of researchers haunted the sites, collecting detailed information on earthworms, carabid beetles, ground-dwelling spiders, EM fungi and mushrooms, nematodes, springtails, salamanders, lichens, and plants, as well as soil carbon and nutrient stocks. Their work would later help guide the design of Weyerhaeuser's adaptive management program.
The upshot of all this research is that even after 80-plus years, differences in biological richness persist between mature second-growth stands and old growth. A specialist looking at lichens on the trees and springtails and nematodes in the soil, for instance, will see a difference. And it is not certain whether the maturing stands, left uncut, will ever match all the characteristics of the old-growth stands nearby.24
For EM fungi, however, the result was different. Trofymow and then graduate student Doug Goodman found that the abundance and diversity of EM fungi in the mature and old-growth forests were quite similar, meaning that sometime after the first half-century or so, the EM fungi in the second-growth forests appear to have recovered.25
There are potential lessons for new forestry in that result: the mature stands used in the chronosequence EM fungi study were created by fire and early logging methods that inadvertently left some in dividual trees. Thus, the sites retained some of the legacies of the old-growth forests that had been cut and burned—hoary "veteran" firs still standing and large stumps and logs littering the floor, as well as rich stocks of organic matter and nutrients in the soil. More importantly, these disturbed forests sit alongside surviving stands of old growth from which EM fungi could disperse.26
Like C1500, the chronosequence site where much of the fungal work took place lies in the Koksilah Valley. After a half-hour on winding dirt roads Ferris pulls the truck to a stop at another dead end. We're still on timber company land, but there are no clearings in sight. To our right is a lush looking fir forest that Trofymow tells us was largely destroyed by wildfire about 90 years ago. On our left is old growth. Both are part of the Koksilah chronosequence.
Trofymow climbs out of the truck and charges into the dense un-derstory of the mature forest, eager to locate the stakes and flagging that demarcate the now overgrown study plots. Outerbridge and I, both seeing the place for the first time and delighted by the contrast with C1500, follow more slowly into the green twilight. The wind sways the canopy far above us, but we cannot feel any stirring. Thick salal and woody deadfall cover the damp, spongy ground.
"Oh wow, look at him," I say, spotting a red mushroom.
"Russula," Outerbridge says.
"Yes, the whole genus is ectomycorrhizal. There are lots of species in the genus and some of them are good edibles. This one, no. It's not poisonous, but not good."
On a bank above a small tumbling creek we spot a whole cluster of little mushrooms. "This one looks like Hebeloma crustulini-forme, the poison pie," she says, crouching down for a closer look.
Mycorrhizal? I ask again.
"Yes, it is," she says, working her way down the soggy slope.
"There's reason to expect about 30 percent of mushrooms are ectomycorrhizal," Outerbridge explains. "A lot of it is circumstantial evidence based on where mushrooms are always found. But then we don't know, is it always under that tree because it's ectomycorrhizal on the roots or because it likes to eat that kind of litter?"
It's exceedingly difficult to dig around a mushroom or a buried truffle and track the hyphal threads back to their origin to see whether the parent fungus makes its living decomposing wood or eating sugars exuded by plant roots.
Traditionally, the taxonomy of fungi has been based primarily on the mushrooms or other reproductive structures. However, many EM fungi have not been linked to their corresponding mushrooms, so another taxonomy has been developed that uses the characteristic anatomical features and DNA profiles of the EM fungal mantle—the sheath formed around a rootlet—on a specific host. It's a bit like classifying fruit trees without linking them to the apples, pears, or other fruit they bear. Trofymow and others are trying to rectify that through an online database aimed at linking up DNA profiles, names, and descriptions of mushrooms with DNA profiles, names, and descriptions of the same fungal species forming ectomycorrhizae.27
At the creek edge, on the ragged end of a mossy, rotting log we find a clump of nondescript brown mushrooms. Outerbridge says they are one of several species of Armillaria, the honey mushroom, one of which causes shoestring root rot disease. This fungus attacks tree roots and sends ropelike bundles of hyphae known as rhizomorphs stretching across vast acreages in its quest for nutrients and new tree roots to parasitize. (These are the same "humongous fungus" mentioned in chapter 1 that may qualify as the largest and oldest organisms on earth.)
We cross the creek one at a time on rocks slick with green fuzz and walk up the far slope. Trofymow finds the center of one of the chronosequence plots, marked by a piece of rebar amid the shrubs. "Okay, this is Goodman's rebar here," he says, pushing the thick shrubs aside. "We didn't find any differences in terms of diversity of ectomycorrhizal fungi in this particular stand compared with the old-growth stand across the road," he recaps. He calls our attention to the tree trunks, all crusted gray with lichens. "This is where we found that the abundance and diversity of arboreal lichens increased from this site to the old-growth site across the road." For whatever reason, lichens either have not taken or cannot take full advantage of their proximity to a colonization source.
As we start down toward the creek again, Outerbridge finds Xy-laria, a wood-decay fungus known as dead man's fingers. The name is apt. I see what look like puffy black fingers poking up from the duff. Before we reach the road she offers me a mushroom that smells like bleach, another that reeks sharply of garlic, and an edible Russala that smells faintly of herring.
When we enter the old-growth stand across the road, the sun is breaking through the clouds. I notice immediately that this forest is much more open, with a sparser but taller canopy of giant Douglas firs and tall hemlocks. When I remark on it, Trofymow consults his chart of stand characteristics. Everything on this site, it seems, has been quantified. Trofymow knows exactly how old this forest was when the chronosequence project began—288 years according to the cores he and his colleagues extracted from the biggest trees. Mean height here is 69 feet, and maximum is 118 feet, compared to a mean of 42 feet and a maximum of 90 feet across the road. Mean density of trees here is 193 per acre compared to 1,357 per acre across the road. A more open forest indeed.
When we arrive back at the Canadian Forest Service Pacific Forestry Centre in Victoria in late afternoon, Outerbridge gives me my first close-up look at the EM fungi I've been hearing about for 2 days. On a laboratory counter she pulls the fir seedling dug up at site C1500 from its plastic bag, plops the ball of roots and dirt into a white plastic tray, and begins gently separating the roots from the soil.
"See these white threads here?" she asks, pointing to what look like masses of spider webs lacing the dark soil. "Those are hyphae." They break up quickly as she works.
Outerbridge cuts off the ends of a dozen roots, rinses them in a sieve, and puts them in a tray of water under a binocular microscope. Peering into the eyepiece, I spot what look like bits of fuzzy white yarn around the orangey root tips.
"That's Pseudotsugaerhiza baculifera. It's sort of a tentative name," she says. "It just means 'Douglas fir mycorrhizae' and indicates a descriptive feature 'bearing small twigs,' probably referring to the needlelike crystals on its hyphae."
At least that creature has a name of sorts. Most of the EM fungi found on her seedlings remain unidentified. She creates descriptions and photographs and refers to them as: "felty translucent white," "chocolate-brown metallic," "pink," "purple blue," "Tomentella-like," or "reddish brown, pubescent, monopodial pinnate to pyramidal in one plane."
What looks like cottony yarn is a fungal mantle; the fuzz is a fan of hyphae.
"Even the finest root hairs of most plants are fatter than most fungal hyphae, and they are fewer in numbers and shorter, so overall they have less surface area," Outerbridge points out. "The idea is to increase the surface area of the root tip for better nutrient absorption." The hyphae can also explore and exploit the tiniest nooks and crannies of the soil where root hairs cannot penetrate.
She projects the microscope view onto a computer screen so that we can both see the next one, a black, tuberous-looking bump that she identifies as Cenococcum geophilum. This is one of the two most common EM fungi she has found on the young firs. "In this sample I'll probably find 40 percent of the root tips occupied by Cenococ-cum," she says.
"I'm surprised I'm not seeing Rhizopogon in this sample because it's usually the most common." She keeps moving the tray slowly. "Oh, here it is."
The brown blobs? I ask.
"Yes, it's a blob because it's a tubercle type. Basically this whole fungal mantle you see is coating several root tips like a mitten over fingers." She cuts into the tubercles with forceps and we can see the root tips bundled inside.
On a nearby root she sees another EM type, a fuzzy yellow-brown ball that looks like a pinch of fiberglass insulation.
What we are seeing is a tiny sampling of EM fungal diversity. Re searchers have identified 2,000 species of EM fungi just from Douglas firs.28 A tree might partner with 10 or more EM types at any given time in its life.29 Some fungi may colonize only a specific tree species, or trees at certain stages of life. For example, Outerbridge has found no chanterelle fungi on any of her 40,000 seedling root tips.
This raises the question of just how many mycorrhizal types a healthy forest needs. What is the threshold below which the integrity of the soil community and thus the health and productivity of the future forest is compromised?
I asked this of David Perry, an emeritus professor at Oregon State and a pioneer of old-growth forest ecology, who has taken part in the annual evaluations of Weyerhaeuser's Coast Forest Strategy. He laughed, then sighed.
"When you compare the soil of any retained forest with a clearcut, you always find differences," he said finally. "We just don't have enough research and experience yet to sort out what that means in the long term for timber production or even for biological diversity. It's pretty clear you can lose too much, but what is too much varies from site to site. We've got a lot of detective work to do to sort this out."
Perry's own work supplies clear cautionary tales from a number of harsh sites where some threshold was crossed and the soil lost its ability to grow a forest. At a fair number of droughty, high-elevation sites from Oregon to Montana, foresters have failed repeatedly in their efforts to get new trees established on clearcuts. The most intensively studied is Cedar Camp, a site in southwest Oregon where Perry and his students spent years trying to determine what triggered degradation so severe that the soil turned to beach sand.30 His first assumption was that the EM fungi had been lost, but it turned out to be more complicated.
"The ectomycorrhizal fungi were actually still there," he recounted. "But they had lost the ability to form mycorrhizae with the tree seedlings. We still don't fully understand that." Perry believes the trigger was probably the herbicide spraying of young shrubs and hardwoods that sprouted in the clearing. Shrubs and hardwoods not only serve as legacy plants that "lifeboat" some of the important mycor-rhizal fungi but also seem to suppress a common soil microbe, the actinomycete Streptomyces. Streptomyces, from which we got the antibiotic streptomycin, chemically suppresses many other microbes and plants, and its proliferation probably reduced root growth and formation of mycorrhizae on replanted fir seedlings. New plantings died year after year as seedlings apparently failed to gather enough nutrients and water to survive their first hot, dry summer. Without trees or shrubs to pump carbon-rich sugars into the soil, the underground food web that depends on that aboveground subsidy began to unravel. The EM fungi hunkered down and went dormant. Deprived of sugars, roots, and hyphae, soil structure deteriorated. The critters most devastated, apparently, were the grazers such as mites that devour microbes and release nitrogen that fertilizes plant growth.
Mike Amaranthus, at that time a Ph.D. student of Perry's, was finally able to break the cycle and get trees growing by planting seedlings in soil taken from an established forest—most likely, Perry believes, because the transplanted soil reintroduced grazers, and their munching of microbes jump-started the nutrient cycle again, allowing the seedlings to grow enough roots to finally take on mycorrhizal partners.31
The full story is much more intricate, as are most tales from life underground. But the clear caution to foresters and land managers is to avoid breaking the links and legacies that allow plants and soils to nurture one another. Ensuring the survival of a diverse soil food web is critical to the recovery of the forest.
It remains to be seen whether Weyerhaeuser and other timber companies and public agencies will continue to monitor the impacts of their new forestry practices and—more important—refine these practices based on the results. The outcome has meaning far beyond the future productivity of our forests. The integrity of forest soils affects a wide range of other aboveground processes, from release of carbon to the atmosphere to erosion, nutrient losses, and water quality, in the immediate watershed and also far downstream.32
The outcome of changes in forestry also has meaning for the biological diversity the forests harbor. Forest issues in British Columbia have attracted keen interest worldwide precisely because the rich plant and animal life of the province remains largely intact.33 Despite a century of intensive timber cutting, wolves, black bears, and cougars still inhabit Vancouver Island. Outerbridge has heard the howl of a wolf as she worked at C1500 in the Koksilah Valley. Will these large and charismatic creatures continue to find suitable forests to live in as second-growth forests on the eastern side of the island and old-growth forests on the west continue to be cut? Most of what little old-growth Douglas fir-dominated forest remains on eastern Vancouver Island exists on privately owned land that is unlikely to be turned into parks or preserves. Because of that, conserving the biodiversity and other values embodied in natural old-growth coastal rain forests in this region depends largely on the success of today's experiments in kinder, gentler forest management.34 Today's timber harvesting practices must be designed to protect life and processes both above and below the ground while the forest recovers, and only by monitoring the fate of key forest species and altering forest practices accordingly can we gauge whether we are succeeding. If we continue to pay attention to and learn from vital but long-overlooked creatures such as mycor-rhizal fungi—and act on what they're telling us—perhaps tomorrow's forests can be as complex, lively, and awe-inspiring as the forests we are cutting today.
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