Off of yesterday's POST regarding how Beetle infested forests impact browsers and carnivores, wanted to explore how these western North American native insects impact forest succession(tree composition)...........What tree species will step forth and "frontier" the dead pines and spruces?...........The USDA, U.S. Forest Service and Colorado Parks & Wildlife say the following---"Mountain pine beetles are likely to create multi-aged forest stands by removing large-diameter trees, reducing stand densities, and providing growing space for other canopy trees and below the main canopy"................."As an example, in the Yellowstone Area after a beetle outbreak in the ‘60 & ‘70s, about 40-70% of the overstory trees died, with surviving trees increasing in growth by 2-3 fold for two decades"........."Pine recruitment(% of forest cover) has been at least equal to previous decades"..........."Pine beetle killed stands recover to pre-MPB stand structure in a century with Logger uncut & partial cut stands dominated by fir and clear Logger cut stands similar in composition to pre-MPB stands dominated by pine"..........."While that has been the path in Yellowstone post beetle outbreak, it is recognized tha regenerating forests can take many different paths, depending on various factors including local climate and the presence of other trees such as aspen, spruce, and fir"..............."Some beetle-killed forests may grow back with more natural diversity than exists today, and others may regenerate back to pure single-aged lodgepole pine".........."Future dominance of species will vary from site to site depending on factors such as site quality, established regeneration, moisture, elevation, and cardinal direction of stands".............

https://www.fs.usda.gov/Internet/FSE_DOCUMENTS/stelprdb5359293.pdf

https://www.motherjones.com/environment/2015/03/bark-pine-beetles-climate-change-diana-six/

Bark Beetles Are Decimating Our Forests. That Might Actually Be a Good Thing.

They gobble up trees and send politicians into a frenzy. But do the bugs know more about climate change than we do?

Maddie Oatman/May/June 2015

There is an eerie feel to this grove of lodgepole pines that I can’t quite put my finger on as entomologist Diana Six tromps ahead of me, hatchet in hand, scanning the southwestern Montana woods for her target. But as she digs the blade into a towering trunk, it finally hits me: the smell. There’s no scent of pine needles, no sharp, minty note wafting through the brisk fall air.

Six hacks away hunks of bark until she reveals an inner layer riddled with wormy passageways. “Hey, looky!” she exclaims, poking at a small black form. “Are you dead? Yeah, you’re dead.” She extends her hand, holding a tiny oval, maybe a quarter of an inch long. Scientists often compare this insect to a grain of rice, but Six prefers mouse dropping: “Beetle in one hand, mouse turd in another. You can’t tell them apart.” She turns to the next few trees in search of more traces. Pill-size holes pock their ashen trunks—a sign, along with the missing pine scent, of a forest reeling from an invasion.

These tiny winged beetles have long been culling sickly trees in North American forests. But in recent years, they’ve been working overtime. Prolonged droughts and shorter winters have spurred bark beetles to kill billions of trees in what’s likely the largest forest insect outbreak ever recorded, about 10 times the size of past eruptions. “A doubling would have been remarkable,” Six says. “Ten times screams that something is really going wrong.”

Mountain pine, spruce, piñon ips, and other kinds of bark beetles have chomped 46 million of the country’s 850 million acres of forested land, from the Yukon down the spine of the Rocky Mountains all the way to Mexico. Yellowstone’s grizzly bears have run out of pinecones to eat because of the beetles. Skiers and backpackers have watched their brushy green playgrounds fade as trees fall down, sometimes at a rate of 100,000 trunks a day. Real estate agents have seen home prices plummet from “viewshed contamination” in areas ransacked by the bugs. And the devastation isn’t likely to let up anytime soon. As climate change warms the North American woods, we can expect these bugs to continue to proliferate and thrive in higher elevations—meaning more beetles in the coming century, preying on bigger chunks of the country.

BEETLEMANIA

From 2000 to 2014, bark beetles destroyed large swaths of forests in the American West—and they’re not done yet.

In hopes of staving off complete catastrophe, the United States Forest Service, which oversees 80 percent of the country’s woodlands, has launched a beetle offensive, chopping down trees to prevent future infestations. The USFS believes this strategy reduces trees’ competition for resources, allowing the few that remain to better resist invading bugs. This theory just so happens to also benefit loggers, who are more than willing to help thin the forests. Politicians, too, have jumped on board, often on behalf of the timber industry: More than 50 bills introduced since 2001 in Congress proposed increasing timber harvests in part to help deal with beetle outbreaks.

But Six believes that the blitz on the bugs could backfire in a big way. For starters, she says, cutting trees “quite often removes more trees than the beetles would”—effectively outbeetling the beetles. But more importantly, intriguing evidence suggests that the bugs might be on the forest’s side. Six and other scientists are beginning to wonder: What if the insects that have wrought this devastation actually know more than we do about adapting to a changing climate?

A BUG’S LIFE

An adult mountain pine beetle lays her eggs under the bark. On her way, she disperses fungi that turn the trees’ tissue into food for her babies, eventually killing the tree.

Though they’re often described as pesky invaders, bark beetles have been a key part of conifer ecosystems for ages, ensuring that groves don’t get overcrowded. When a female mountain pine beetle locates a frail tree, she emits a chemical signal to her friends, who swarm to her by the hundreds. Together they chew through the bark until they reach the phloem, a cushy resinous layer between the outer bark and the sapwood that carries sugars through the tree. There, they lay their eggs in tunnels, and eventually a new generation of beetles hatches, grows up, and flies away. But before they do, the mature beetles also spread a special fungus in the center of the trunk. And that’s where things get really interesting.

Pine Beetles

Six focuses on the “evolutionary marriage” of beetle and fungi at her four-person lab at the University of Montana, where she is the chair of the department of ecosystems and conservation sciences. Structures in bark beetles’ mouths have evolved to carry certain types of fungi that convert the tree’s tissue into nutrientsfor the bug. The fungi have “figured out how to hail the beetle that will get them to the center of the tree,” Six says. “It’s like getting a taxi.” The fungi leave blue-gray streaks in the trees they kill; “blue-stain pine” has become a specialty product, used to make everything from cabins to coffins to iPod cases.

A healthy tree can usually beat back invading beetles by deploying chemical defenses and flooding them out with sticky resin. But just as dehydration makes humans weaker, heat and drought impede a tree’s ability to fight back—less watermeans less resin. In some areas of the Rocky Mountain West, the mid-2000s was the driest, hottest stretch in 800 years. From 2000 to 2012, bark beetles killed enough trees to cover the entire state of Colorado. “Insects reflect their environment,” explains renowned entomologist Ken Raffa—they serve as a barometer of vast changes taking place in an ecosystem.

Spruce Beetle

Typically, beetle swells subside when they either run out of trees or when long, cold winters freeze them off (though some larvae typically survive, since they produce antifreeze that can keep them safe down to 30 below). But in warm weather the bugs thrive. In 2008, a team of biologists at the University of Colorado observed pine beetles flying and attacking trees in June, a month earlier than previously recorded. With warmer springs, the beetle flight season had doubled, meaning they could mature and lay eggs—and then their babies could mature and lay eggs—all within one summer.

That’s not the only big change. Even as the mountain pine beetles run out of lodgepole pines to devour in the United States, in 2011 the insects made their first jump into a new species of tree, the jack pine, in Alberta. “Those trees don’t have evolved defenses,” Six says, “and they’re not fighting back.” The ability to invade a new species means the insects could begin a trek east across Canada’s boreal forest, then head south into the jack, red, and white pines of Minnesota and the Great Lakes region, and on to the woods of the East Coast. Similarly, last year, the reddish-black spruce beetle infested five times as many acres in Colorado as it did in 2009. And in the last decade, scientists spotted the southern pine beetle north of the Mason-Dixon Line for the first time on record, in New Jersey and later on Long Island. As investigative journalist Andrew Nikiforuk put it in his 2011 book on the outbreaks, we now belong to the “empire of the beetle.”

In a weird way, all of this is exciting news for Six: She is not only one of the world’s foremost experts in beetle-fungi symbiosis, but proud to be “one of the few people in Montana that thinks bark beetles are cute.” (She’s even brewed her own beer from beetle fungi.) As a child, she filled her bedroom in Upland, California, with jars of insects and her fungus collection. But as a teenager, she got into drugs, quit high school, and started living on the streets. Nine years later, she attended night school, where teachers urged her to become the first in her family to go to college. And when she finally did, she couldn’t get enough: classes in microbiology and integrated pest management led to a master’s degree in veterinary entomology, then a Ph.D. in entomology and mycology and a postdoc in chemical ecology, focused on insect pheromones.