Submitted by Charlene Uhl
Article appearing in the Washington Post, Dec. 18 2019
By Adrian Higgins Columnist
It is hard to overstate the value and cultural importance of the American chestnut tree for those who came before us.
The native hardwood was once so ubiquitous, it has been said, that a squirrel could travel from Maine to Georgia in the chestnut canopy. The largest trees, spreading 100 feet or more, dropped 10 bushels of nuts, and in the fall the ground was covered with a nut blanket four inches deep, writes sociologist Donald E. Davis in a 2005 paper.
The bears and turkeys feasted, the farmer’s hogs feasted, and the people who lived in chestnut territory feasted — on that sweetened Appalachian ham but also on the economic value of the trees and their nuts. The chestnut’s arrow-straight timber was valued for its size and rot resistance and today endures in the posts and beams of old farmhouses and barns.
For us city folk, the chestnut evokes everything that is nostalgic about yuletide season, the notion of a vendor plying hot roasted chestnuts on a street corner. The aroma, the warmth in the hand, the nutty flavor all conjure one of the more cuddly images of a Dickensian world.
, this diminished holiday custom is carried on with nuts from Asia and Europe, which are bigger but less sweet.
The American chestnut was killed off by the arrival of a blight in 1904 that within a few decades had virtually wiped out an entire, dominant species. In modern parlance the fungus, Cryphonectria parasitica, went viral.
This environmental catastrophe is widely known. Not so broadly understood is that we are closer than ever to returning the American chestnut to its old haunts — or something akin to it. This resurrection has been several decades in the making and has taken two parallel tracks. The first is in the slow, methodical work of traditional hybridization, attempting with each successive generation a tree that will be naturally resistant to the fungus. This has been led by the American Chestnut Foundation, based in Asheville, N.C. The second is by way of genetic modification, undertaken by scientists at the State University of New York in partnership with the foundation. In a world wary of organism-mixing in the lab, this has proved more controversial.
Naturally resistant trees can reach nut-bearing age before the blight knocks them back. This tree is in western North Carolina. (American Chestnut Foundation) The winter garden is full of promise and productivity.
The conventional breeding began by crossing the blight-tolerant Chinese chestnut with some surviving American chestnut individuals that had proved resistant to the fungus, if only to die back to the roots after reaching nut-bearing age.
The foundation was created in 1983 by plant scientists and others who saw the potential of systematic development of a blight-resistant tree through a series of “backcrosses” in which successive generations of American-Chinese hybrids could be bred with resistant American chestnuts. Once these crosses produced trees that were carrying chiefly the American chestnut genome — as much as 90 percent — they were crossed with each other. The challenge has been to select seedlings with enough Chinese blood in them to ward off the disease and yet still look like the American chestnut. At maturity, the American tree is tall and spreading with a thick, straight trunk. The Chinese species is shorter and more branching.
Most of this work goes on at a research station in southwest Virginia named Meadowview Research Farms. The foundation is supported by 5,000 members and chapters in 16 states.
Jared Westbrook, the foundation’s science director, said that of 60,000 seedlings planted and evaluated, 4,000 have made the cut so far. That number will be reduced to 2,000 in the coming months, and a final cut will leave 600 trees by 2021 as the culmination of the breeding program. These will be used to re-populate the Appalachian forest — though earlier-generation trees produced at Meadowview have already been planted on 40 private, state and national sites in the chestnut’s historical range. Westbrook is using a technique called genomic selection to pick the finalists — by analyzing their DNA he can identify individuals with the desired traits.
This is not to be confused with genetic modification, which is the tack employed by William Powell and his colleagues at SUNY’s College of Environmental Science and Forestry. They have used a wheat gene to counter the effects of the disease and have asked the Agriculture Department to sign off on its release. Also, Powell said, the Environmental Protection Agency will decide whether the antifungal properties constitute a fungicide, which would require pesticide registration. In addition, the Food and Drug Administration will determine whether the nuts are safe to eat.
The foundation is working with the researchers. “If it gets through the review process, the American Chestnut Foundation would breed that gene into a diverse population,” Westbrook said. “We are using all the tools available to us.”
The genetically engineered or transgenic chestnut is facing opposition from an alliance of environmental groups named StopGEtrees, which claims its release into the wild would be “a massive and irreversible experiment” and pave the way for other forest tree species to be genetically engineered and released.
“This would be the first one to be released into nature,” said Rachel Smolker, co-author of a report critical of the plan. The restoration of the American chestnut is such an appealing idea that the proponents of genetic engineering are using it to win acceptance of the broader biotechnology, she says. “It’s about winning public support for genetically engineered trees, which has met with tremendous public resistance,” she said. “It’s a very deliberate strategy. A tree engineered for biofuels doesn’t win over the public in the same way.”
Powell says the bacterium he used to carry the wheat gene into the chestnut chromosome is already found, naturally, in the DNA of some tree species, including the walnut. “Walnut is a natural GMO,” he said. The biotechnology “can be applied to other trees,” he says. “But it’s a good thing, it can save more trees.”
This fall, residents of the Lyon Park neighborhood of Arlington County gathered in their community park to plant two non-transgenic saplings from the chestnut foundation to mark Lyon Park’s centennial. They are just a few inches tall, but they are latent giants. “We are protecting them and doing the best we can,” said resident Gray Handley. A hundred years after the demise of the American chestnut, there is hope that future generations will witness something denied ours, the return of the big old American chestnut.
Seeing a ton of acorns on the ground? It must be a ‘mast’ year for oaks.
By Emily Moran, Washington Post 11.26.19
(submitted by Charlene Uhl, Class X)
If you have oak trees in your neighborhood, perhaps you’ve noticed that some years the ground is carpeted with their acorns, and some years there are hardly any. Biologists call this pattern, in which all the oak trees for miles around make either lots of acorns or almost none, “masting.”
In New England, naturalists have declared this fall a mast year for oaks: All the trees are making tons of acorns all at the same time. Many other types of trees, from familiar North American species such as pines and hickories to the massive dipterocarps of Southeast Asian rainforests, show similar synchronization in seed production. But why and how do trees do it?
Every seed contains a packet of energy-rich starch to feed the baby tree that lies dormant inside. This makes them a tasty prize for all sorts of animals, from beetles to squirrels to wild boar.
If trees coordinate their seed production, these seed-eating animals are likely to get full long before they eat all the seeds produced in a mast year, leaving the rest to sprout.
For trees like oaks that depend on having their seeds carried away from the parent tree and buried by animals like squirrels, a mast year has an extra benefit. When there are lots of nuts, squirrels bury more of them instead of eating them immediately, spreading oaks across the landscape.
Getting in sync
It’s still something of a mystery how trees synchronize their seed production to get these benefits, but several elements seem to be important. First, producing a big crop of seeds takes a lot of energy. Trees make their food through photosynthesis: using energy from the sun to turn carbon dioxide into sugars and starch. There’s only so many resources to go around, though. Once trees make a big batch of seeds, they may need to switch back to making new leaves and wood for a while, or take a year or two to replenish stored starches, before another mast.
But how do individual trees decide when that mast year should be? Weather appears to be important, especially spring weather. If there’s a cold snap that freezes the flowers of the tree — and yes, oaks do have flowers, they’re just extremely small — then the tree cannot produce many seeds the following fall.
A drought in the summer could also kill developing seeds. Trees will often shut the pores in their leaves to save water, which also reduces their ability to take in carbon dioxide for photosynthesis.
Because all the trees within a local area are experiencing essentially the same weather, these environmental cues can help coordinate their seed production, acting like a reset button they’ve all pushed at the same time.
A third intriguing possibility that researchers are still investigating is that trees are “talking” to one another via chemical signals. Scientists know that when a plant is damaged by insects, it often releases chemicals into the air that signal to its other branches and to neighboring plants that they should turn on their defenses. Similar signals could potentially help trees coordinate seed production.
Investigation of tree-to-tree communication is still in its infancy, however. For instance, ecologists recently found that chemicals released from the roots of the leafy vegetable mizuna can affect the flowering time of neighboring plants. While this sort of communication is unlikely to account for the rough synchronization of seed production over dozens or even hundreds of miles, it could be important for syncing up a local area.
Masting and the food web
Whatever the causes, masting has consequences that flow up and down the food chain. For instance, rodent populations often boom in response to high seed production. This in turn results in more food for rodent-eating predators such as hawks and foxes; lower nesting success for songbirds, if rodents eat their eggs; and potentially higher risk of transmission of diseases such as hantavirus to people. If the low seed year that follows causes the rodent population to collapse, the effects are reversed.
The seeds of masting trees have also historically been important for feeding human populations, either directly or as food for livestock. Acorns were a staple in the diet of Native Americans in California, with families carefully tending particular oaks and storing the nuts for winter. In Spain, the most prized form of ham still comes from pigs that roam through the oak forests, eating up to 20 pounds of acorns each day.
So the next time you take an autumn walk, check out the ground under your local oak tree — you might just see the evidence of this amazing process.
Emily Moran is assistant professor of Life and Environmental Sciences at the University of California at Merced. This report was originally published on theconversation.com.
Washington Post 11.26.19
Article from NPR Website
October 16, 2019 12:08 PM ET
Forest biologist Patricia Maloney is raising 10,000 sugar pine seedlings descended from trees that survived California's historic drought.
When California's historic five-year drought finally relented a few years ago the tally of dead trees in the Sierra Nevada was higher than almost anyone expected: 129 million. Most are still standing, the dry patches dotting the mountainsides.
But some trees did survive the test of heat and drought. Now, scientists are racing to collect them, and other species around the globe, in the hope that these "climate survivors" have a natural advantage that will allow them to better cope with a warming world.
On the north shore of Lake Tahoe, Patricia Maloney, a UC Davis forest and conservation biologist, hunts for these survivors. Most people focus on the dead trees, their brown pine needles obvious against the glittering blue of the lake. But Maloney tends not to notice them. "I look for the good," she says. "Like in people, you look for the good, not the bad. I do the same in forest systems."
Maloney studies sugar pines, a tree John Muir once called the "king" of conifers. "They have these huge, beautiful cones," she says. "They're stunning trees." The sugar pines on these slopes endured some of the worst water stress in the region. Winter snowpack melts fastest on south-facing slopes, leaving the trees with little soil moisture over the summer. That opens the door for the trees' tiny nemesis, which would deal the fatal blow.
Here you have some really good mountain pine beetle galleries," Maloney says, as she peels the bark off a dead sugar pine to show winding channels eaten into the wood. "Like little beetle highways." Pine beetle outbreaks are a normal occurrence in the Sierra. As the beetles try to bore into the bark, pine trees can usually fight them off by spewing a sticky, gummy resin, entrapping the insects. But trees need water to make resin.
During the drought, "the tank ran dry, and they weren't able to mobilize any sort of resin," Maloney says.
Evolution is a tool that we can bring to bear in helping us get through this future.
But next to this dead tree, Maloney points to one towering above, the same exact species, that has healthy green pine needles. Somehow, it was able to fight the beetles off and survive the drought. As she's found more and more of these survivors, Maloney has studied them, trying to figure out their secret. "What we found is that the ones that were green, like this one, were more water-use efficient than their dead counterparts," she says. In other words, the survivors had an innate ability to do more with less. Individual members of any species can vary dramatically, something tied to genetic differences. That diversity comes in handy when environmental conditions change.
The drought, heat and beetle outbreaks in recent years put extreme pressure on sugar pines, creating a natural experiment that weeded out all but the toughest. "I think what we're seeing is contemporary natural selection," Maloney says. Now, she's trying to ensure their descendants survive.
Inside a greenhouse at her Tahoe City field station, Maloney shows off a sea of young green trees in their own containers. These 10,000 sugar pine seedlings grew from seeds Maloney and her team collected from 100 of the surviving sugar pines. Over the next year, these young trees will be replanted around Lake Tahoe, both on national forest and private land. The hope is the trees, due to their genetics, will be better able to handle a warming climate, more extreme droughts and more frequent beetle outbreaks. "These survivors matter," Maloney says. She plans to study the genetics of these trees as they grow, research that could help in other climate-threatened forests.
And Maloney's not alone in searching for species that can handle the warming climate. "Evolution is a tool that we can bring to bear in helping us get through this future," says Steve Palumbi, a biology professor at Stanford University, who has been looking for coral that can handle heat. Coral reefs are bleaching and dying as oceans warm, so Palumbi is growing surviving corals in the hope they can build new reefs full of "super corals." Reefs aren't just tourist attractions, he says. They're also biodiversity hotspots that protect coastlines from flooding by absorbing wave energy. "If it gives us another decade, if it gives us another two generations, that'll be good, we'll take it," he says. "I see these next 80 years as the time where we have to save as much as possible."
But beyond that, it gets trickier, given the rate the climate is changing. "The question in the future is: When the environment changes and it changes really fast, can these populations keep up?" he asks. "How fast can they adapt? How much help will they give us in keeping those ecosystems going?" Ultimately, Palumbi says, the best solution for these species is for humans to curb emissions of heat-trapping gases. In the meantime, scientists are trying to buy them a little more time.
© 2019 npr
See also: The Tree Canopy Biota video
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