Oregon forest has an ancient unseen killer: ‘Humongous Fungus’

By Jacob Jones
Atop a low ridge in the heart of Oregon’s Blue Mountains, Michael McWilliams pushes through brittle branches and scrambles over toppled logs and decay. Bare trunks tower overhead, but the U.S. Forest Service pathologist focuses low. He’s searching for something that lurks underfoot, hidden despite its immense size.

A sickly fir tree is where he finally stops and kneels. He begins raking at its roots with the curved adz blade of his wood-handled Pulaski. The tool clinks and scrapes, revealing a cream-colored film beneath the bark. It’s an inches-long glimpse of what is likely to be the world’s largest single living organism, a fungus thousands of years old yet still capable of strangling an entire forest.

“Yeah, baby,” McWilliams says, scraping away. “This is a tree killer.”

Dubbed the “Humongous Fungus,” the honey mushroom officially classified as Armillaria ostoyae spreads underground through trees’ root systems. It fruits an edible honey-brown cap just a few weeks each year, typically after the first fall rains. The rest of the year it’s elusive, its presence subterranean.

But what a presence that is: Researchers estimate that the colony here covers 3.7 square miles and may weigh a collective 35,000 tons.

“If you can expand your perception of what a mushroom is,” McWilliams says, “you can see it everywhere.”

Another Forest Service scientist first noticed the widespread die-off of local tree stands in 1988. Greg Whipple linked the problem to armillaria, then worked with others to map samples across hundreds of acres. The teams eventually confirmed that many shared the same DNA.

Whipple, now retired, remembers how his early attempts to limit the damage by clearing out infected areas drew death threats. Timber wars were raging between loggers and environmentalists, upending federal forest management in the Pacific Northwest.

“It was my lesson into politics,” he says.

Decades later, the killer fungus carries on, growing 1 to 3 feet a year. In satellite images of the Malheur National Forest in Eastern Oregon, rusty streaks of dead canopy and the pale, crisscrossed skeletons of downed trees now litter the infestation areas.

Researchers believe part of the colony could date to 6600 B.C. “It’s one of those things that makes you realize mankind is pretty insignificant,” Whipple says. “You realize just how small of a blip we are on the landscape.”

Root disease kills more trees in this region than bugs or beetles, but it moves slowly, picking winners and losers over generations. The fungus remakes the forest as it expands, choking off fir or pine while sparing more tolerant larch. Stunted saplings turn orange as the fungus takes hold. Trees often keel over to reveal roots completely eaten away.

Source: Oregon forest has an ancient unseen killer: ‘Humongous Fungus’ – The Bulletin, 2019-09-01

Kauri trees share roots with other trees, AUT research shows

A bizarre insight from our kauri means we should view forests as ‘super-organisms’.

Kiwi scientists have been astonished to find how kauri stumps can keep themselves alive by feeding off water from neighbouring trees.

The AUT researchers behind the ground-breaking discovery say it should mean we view trees not as individuals, but members of a forest ecosystem that’s essentially a “super-organism”.

Further, their findings could have big implications for tackling the disease killing kauri across the upper North Island.

In the new study, published in iScience this week, AUT’s Dr Martin Bader and Associate Professor Sebastian Leuzinger described how trees surrounding kauri stumps offer them a form of life support, possibly in exchange for access to larger root systems.

It was an insight the pair stumbled across while hiking in West Auckland, and spotting an unusual-looking stump.

“It was odd, because even though the stump didn’t have any foliage, it was alive,” Leuzinger said.

They decided to investigate how the nearby trees were keeping the tree stump alive by measuring water flow in both the stump and the surrounding trees belonging to the same species.

They found that the water movement in the tree stump was strongly negatively correlated with that in the other trees.

These measurements suggest the roots of the stump and surrounding conspecific trees were grafted together, Leuzinger said.

Root grafts can form between trees once a tree recognises that a nearby root tissue, although genetically different, is similar enough to allow for the exchange of resources.

“This is different from how normal trees operate, where the water flow is driven by the water potential of the atmosphere,” Leuzinger said.

“In this case, the stump has to follow what the rest of the trees do or else use osmotic pressure to drive water flow, because since it lacks transpiring leaves, it escapes the atmospheric pull.”

But while root grafts are common between living trees of the same species, the pair were interested in why a living kauri tree would want to keep a nearby stump alive.

“For the stump, the advantages are obvious— it would be dead without the grafts, because it doesn’t have any green tissue of its own,” Leuzinger said.

“But why would the green trees keep their grandpa tree alive on the forest floor while it doesn’t seem to provide anything for its host trees?”

One explanation, Leuzinger said, is that the root grafts formed before one of the trees lost its leaves and became a stump.

The grafted roots expand the root systems of the trees, allowing them to access more resources such as water and nutrients.

They also increased the stability of the trees on the steep forest slope.

Source: Kauri trees share roots with other trees, AUT research shows – NZ Herald, 2019-08-05

Trees talk to each other and scientists have mapped the network

By Robert Dalheim
Scientists discovered that trees talk to each other through the Wood Wide Web. And now, they’ve mapped it.

Do trees actually talk to each other? And if so, how do they do it?

Just over 20 years ago, ecologist Suzanne Simard discovered that trees do communicate with each other, and it’s through a fungal network scientists have nicknamed the Wood Wide Web.

And now, an international team of scientists has created the first global map of the vast underground network. They did this by creating a computer algorithm to analyze a database from the Global Forest Inititiave, which includes 1.2 million trees in more than 70 countries.

The algorithm takes into account the different fungal species that associate with each tree species. It also takes into account local climate factors – which the scientists say has the biggest role to play.

“It’s the first time that we’ve been able to understand the world beneath our feet, but at a global scale,” Thomas Crowther, an author of the study from ETH Zurich, told the BBC. “Just like an MRI scan of the brain helps us to understand how the brain works, this global map of the fungi beneath the soil helps us to understand how global ecosystems work.

“What we find is that certain types of microorganisms live in certain parts of the world, and by understanding that we can figure out how to restore different types of ecosystems and also how the climate is changing,” he said.

Source: Trees talk to each other and scientists have mapped the network – Woodworking News, 2019-05-16

Eastern forests shaped more by Native Americans’ burning than climate change

By Jeff Mulhollem
Native Americans’ use of fire to manage vegetation in what is now the Eastern United States was more profound than previously believed, according to a Penn State researcher who determined that forest composition change in the region was caused more by land use than climate change.

“I believe Native Americans were excellent vegetation managers and we can learn a lot from them about how to best manage forests of the U.S.,” said Marc Abrams, professor of forest ecology and physiology in the College of Agricultural Sciences. “Native Americans knew that to regenerate plant species that they wanted for food, and to feed game animals they relied on, they needed to burn the forest understory regularly.”

Over the last 2,000 years at least, according to Abrams — who for three decades has been studying past and present qualities of eastern U.S. forests — frequent and widespread human-caused fire resulted in the predominance of fire-adapted tree species. And in the time since burning has been curtailed, forests are changing, with species such as oak, hickory and pine losing ground.

“The debate about whether forest composition has been largely determined by land use or climate continues, but a new study strongly suggests anthropogenic fire has been the major driver of forest change in the East,” said Abrams. “That is important to know because climate change is taking on an ever larger proportion of scientific endeavor.”

Source: Eastern forests shaped more by Native Americans’ burning than climate change – Penn State University, 2019-05-21

Resilience of Yellowstone’s forests tested by unprecedented fire

By Kelly April Tyrrell, University of Wisconsin
In August 2016, areas of Yellowstone National Park that burned in 1988 burned again. Shortly after, in October 2016, ecologist Monica Turner and her team of graduate students visited the park to begin to assess the landscape.

“We saw these areas where everything was combusted and we hadn’t seen that previously,” says Turner, a professor of integrative biology at the University of Wisconsin–Madison who has closely studied Yellowstone’s response to fire since 1988. “That was surprising.”

In a study published this week [May 20, 2019] in the Proceedings of the National Academy of Sciences, Turner and her team describe what happens when Yellowstone — adapted to recurring fires every 100 to 300 years — instead burns twice in fewer than 30 years. Yellowstone as we know it faces an uncertain future, the researchers say, and one of the big questions they hope to answer is whether the forests can recover.

“We were essentially able to reconstruct what the forest looked like before the fire happened, how many trees there were and how big they would have been,” Braziunas says. “Because we also measured nearby stands (of trees) that didn’t burn, we could compare what happens after the reburns and game out the scenarios in the model.”

The estimate, she and Turner say, represents a best-case, conservative scenario. With a warming climate and increased frequency of drought, the forests are likely to burn again in short intervals.

However, the forest has long shown itself to be resilient.

“The landscapes are going to look different than they have in the past,” says Turner, “but that doesn’t mean they won’t be beautiful. There will be species that benefit and species that see their ranges contract.”

“Change is going to happen and change is going to happen more quickly than we thought it would,” she adds. “We are learning how the system responds, but we don’t know to what degree it will be resilient or adapt in the future. But I am not ready to write it off. We have been surprised in the past.”

Source: Resilience of Yellowstone’s forests tested by unprecedented fire – Wildfire Today, 2019-05-21

Researchers map symbiotic relationships between trees and microbes worldwide

by Taylor Kubota, Stanford University
In and around the tangled roots of the forest floor, fungi and bacteria grow with trees, exchanging nutrients for carbon in a vast, global marketplace. A new effort to map the most abundant of these symbiotic relationships—involving more than 1.1 million forest sites and 28,000 tree species—has revealed factors that determine where different types of symbionts will flourish. The work could help scientists understand how symbiotic partnerships structure the world’s forests and how they could be affected by a warming climate.

In and around the tangled roots of the forest floor, fungi and bacteria grow with trees, exchanging nutrients for carbon in a vast, global marketplace. A new effort to map the most abundant of these symbiotic relationships—involving more than 1.1 million forest sites and 28,000 tree species—has revealed factors that determine where different types of symbionts will flourish. The work could help scientists understand how symbiotic partnerships structure the world’s forests and how they could be affected by a warming climate.

Source: Researchers map symbiotic relationships between trees and microbes worldwide – Phys.org, 2019-05-15

Can Humans Help Trees Outrun Climate Change?

By Moises Velasquez-Manoff
A dark synergy of extreme weather and emboldened pests could imperil vast stretches of woodland. Foresters are only starting to wrestle with solutions.

Foresters began noticing the patches of dying pines and denuded oaks, and grew concerned. Warmer winters and drier summers had sent invasive insects and diseases marching northward, killing the trees.

If the dieback continued, some woodlands could become shrub land.

Most trees can migrate only as fast as their seeds disperse — and if current warming trends hold, the climate this century will change 10 times faster than many tree species can move, according to one estimate. Rhode Island is already seeing more heat and drought, shifting precipitation and the intensification of plagues such as the red pine scale, a nearly invisible insect carried by wind that can kill a tree in just a few years.

The dark synergy of extreme weather and emboldened pests could imperil vast stretches of woodland.

So foresters in Rhode Island and elsewhere have launched ambitious experiments to test how people can help forests adapt, something that might take decades to occur naturally. One controversial idea, known as assisted migration, involves deliberately moving trees northward. But trees can live centuries, and environments are changing so fast in some places that species planted today may be ill-suited to conditions in 50 years, let alone 100. No one knows the best way to make forests more resilient to climatic upheaval.

These great uncertainties can prompt “analysis paralysis,” said Maria Janowiak, deputy director of the Forest Service’s Northern Institute of Applied Climate Science, or N.I.A.C.S. But, she added, “We can’t keep waiting until we know everything.”

Source: Can Humans Help Trees Outrun Climate Change? – New York Times, 2019-04-25

Hidden giants in forest soils

Only a fraction of the microbes residing in, on and around soils have been identified through efforts to understand their contributions to global nutrient cycles. Soils are also home to countless viruses that can infect microbes, impacting their ability to regulate these global cycles. In Nature Communications, giant virus genomes have been discovered for the first time in a forest soil ecosystem by researchers from the DOE Joint Genome Institute and the University of Massachusetts-Amherst.

Characterizing the diversity of microbial cells in a handful of soil is so complex it was considered impossible. To date, only a small fraction of the microbes residing in, on and around soils have been identified as part of efforts to understand their contributions to the global carbon cycle, and to other nutrient cycles. Soils are also home to countless viruses that can infect microbes, impacting their ability to regulate these global cycles.

Reported November 19, 2018, in Nature Communications, giant virus genomes have been discovered for the first time in a forest soil ecosystem by researchers from the U.S. Department of Energy (DOE) Joint Genome Institute (JGI), a DOE Office of Science User Facility, and the University of Massachusetts-Amherst (UMass Amherst). As the name implies, giant viruses are characterized by disproportionately large genomes and virions that house the viruses’ genetic material. They have been frequently found within protists and algae, and thus they are believed to have a significant impact on their hosts’ population dynamics and the planet’s biogeochemical cycles.

Source: Hidden giants in forest soils – EurekAlert, 2018-11-19

Take a Look at How Quickly a Forest Can Recover From Fire

By Andy Newman
Though it appears destructive, fire in the New Jersey Pinelands is a force of renewal.
On April 22, a spring wildfire roared through Penn State Forest in the New Jersey Pine Barrens, sending 100-foot flames shooting from the crowns of the pitch pines. The fire consumed half a square mile in 40 minutes and could be seen from space. By the time the New Jersey Forest Fire Service got it under control, it had burned 843 acres, an area the size of Central Park.

A week later, even as ash still swirled through air heavy with the creosote scent of burned resin and a cedar log smoldered at the edge of a swamp, the forest was being reborn. Pine cones that open only under extreme heat had released their seeds. Though the trees themselves were charred, almost all survived the fire. Where chest-high blueberry and huckleberry had burned down to pointy stubs, tufts of grass were sprouting.

Destructive fires in the West dominated the news this summer, but for eons fire has been not just an inevitable feature of the landscape, but essential to the forest’s health and continuity. In the vast wilderness of the Pine Barrens, the forest regenerates so fast that scientists studying the physics of fire use it as a laboratory.

Eleven weeks after the fire in Penn State Forest, at the height of summer’s greening, new blueberry bushes were already shin high. A grass that flowers only after fire had put forth purple-brown seeds. And scattered all through the fire site, bursts of bright-green pitch-pine needles grew straight out of scorched trunks.

Source: Take a Look at How Quickly a Forest Can Recover From Fire – New York Times, 2018-09-25

Scientists thought they had created the perfect tree. But it became a nightmare.

By Adrian Higgins
A pear seedling selection named Bradford was cloned by the gazillion to become the ubiquitous street tree of America’s postwar suburban expansion. Then it turned invasive.

Carole Bergmann pulls her small parks department SUV into an aging 1980s subdivision in Germantown, Md., and takes me to the edge of an expansive meadow. A dense screen of charcoal-gray trees stands between the open ground and the backyards of several houses. The trees are callery pears, the escaped offspring of landscape specimens and street trees from the neighborhood. With no gardener to guide them, the spindly wildlings form an impenetrable thicket of dark twigs with three-inch thorns.

Bergmann, a field botanist for the Montgomery County Parks Department, extricates herself from the thicket and in the meadow shows me that what I take to be blades of grass are actually shoots of trees, mowed to a few inches high. There are countless thousands, hiding in plain sight in Great Seneca Stream Valley Park. If it were not cut back once a year, the meadow would become like the adjacent screen, wall upon wall, acre upon acre of black-limbed, armored trees worthy of Sleeping Beauty’s castle.

“You can’t mow this once and walk away,” said Bergmann, who began her 25-year career in the department as a forest ecologist but has been consumed by an ever-pressing need to address the escape of the Bradford pear and other variants of callery pear, a species that originated in China, along with other invasive exotics.

Source: Scientists thought they had created the perfect tree. But it became a nightmare. – The Washington Post, 2018-09-17