Hexbyte Glen Cove Trees found to reduce land surface area temperatures in cities up to 12°C

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Credit: Unsplash/CC0 Public Domain

A team of researchers with the Institute for Atmospheric and Climate Science, ETH Zurich, has found evidence that indicates that stands of trees can reduce land surface area temperatures in cities up to 12°C. In their paper published in the journal Nature Communications, the group describes how they analyzed satellite imagery for hundreds of cities across Europe and what they learned.

Prior research has suggested that adding to cities can help reduce high air temperatures during the warm months—cities are typically hotter than surrounding areas due to the huge expanses of asphalt and cement that absorb heat. In this new effort, the researchers looked at possible impacts on land surface areas instead of air temperatures. Such temperatures are not felt as keenly as air temperatures by people in the vicinity because it is below their feet rather than surrounding them.

The work by the team involved analyzing data from satellites equipped with land surface temperature sensors. In all, the researchers poured over data from 293 cities across Europe, comparing land surface temperatures in parts of cities that were covered with trees with similar nearby urban areas that were not covered with trees. For comparison purposes, they did the same for rural settings covered in pastures and farmland.

They found urban areas with trees typically had land surface temperatures that were two to four times cooler than similar areas nearby that had no tree cover. Such differences translated to approximately 0 to 4 K lower than surrounding areas in parts of Southern Europe—in other regions, such as Central Europe, the differences were as high as 8 to 12 K. Interestingly, the researchers found no such differences in rural areas. And they found no differences for other types of vegetation in the cities.

The researchers note that trees are able keep the ground cooler due to the shade they provide, which suggests they help reduce building surface temperatures in similar ways. Their work highlights the impact that adding tree cover to can have.

More information:
Jonas Schwaab et al, The role of urban trees in reducing land surface temperatures in European cities, Nature Communications (2021). DOI: 10.1038/s41467-021-26768-w

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Trees found to reduce land surface area temperatures in cities up to 12°C (2021, November 26)
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Hexbyte Glen Cove Researchers identify new threat to American chestnut trees

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Emily Dobry, a graduate student conducting research at the Lake Erie Regional Grape Research and Extension Center, has identified a new fungal threat to the American chestnut tree. Credit: Penn State Behrend

For lumber companies, the American chestnut was a nearly perfect tree—tall, straight, rot-resistant and easy to split. It also was prolific, sending up new shoots that grew quickly.

In the early 1900s, the species made up a substantial portion of eastern hardwood forests. There were nearly four billion American chestnut trees in the United States, each growing up to 100 feet, with trunks four to seven feet thick. Healthy trees lived for 400 to 600 years, producing several bushels of nuts every year.

Today, however, it can be difficult to find a healthy American chestnut. A fungal pathogen on trees imported from Japan and China wiped the species out in less than 40 years. That loss is considered to be the greatest ecological disaster to ever strike the world’s forests.

“The pathogen is native to Chinese and Japanese chestnuts, so the two co-evolved,” said Emily Dobry, a Penn State Behrend graduate now in Penn State’s plant sciences horticulture master’s-degree program. She is doing research work at the University’s Lake Erie Regional Grape Research and Extension Center (LERGREC) in North East. “The American chestnut had never been exposed to it before, however, so it had little natural resistance. Think of it as smallpox for trees.”

Today, there are fewer than 1,000 American chestnut trees, largely in isolated areas outside of the tree’s historical range in the eastern half of the United States, along the Appalachian mountain ridge and throughout New England.

A few can be found at LERGREC, where researchers have been conducting a trial since 2013 with 15 chestnut trees—five each of the American, Chinese, and American-Chinese hybrid species developed by scientists, all planted in one long row.

“The idea was to plant American and Chinese chestnuts side by side with some of the hybrids that have been developed, and to allow them to be challenged with chestnut blight over the years,” said Bryan Hed, a plant pathologist at LERGREC.

“Most of the trees have suffered dieback from disease, insects or weather and have had to be cut back and renewed,” he said. “The hybrid trees are notable exceptions: Three of them are currently 17 to 21 feet in height.”

Trees are renewed using sucker growth from the original rootstock.

“The American chestnut is now designated as ‘functionally extinct,'” which means that although the species still technically survives, it cannot reproduce,” Dobry said. “The shoots rarely grow large enough to produce nuts, and therefore, future generations.”

The most promising hope for the American chestnut now is probably transgenic—the development of a genetically modified tree. Scientists are trying to engineer a tree that is as close to an American chestnut as possible, with just enough genetic material from the Chinese chestnut to resist the blight.

“Researchers have developed partially blight-resistant transgenic American chestnuts that are capable of surviving infection from the pathogen that causes blight,” Dobry said. “It doesn’t kill the pathogen; it’s still present, but it doesn’t destroy the tree.”

The current balance of species in U.S. forests could pose another problem as scientists try to reintroduce the American chestnut: The oak tree has risen to fill its place.

“It will be a challenge for the American chestnut to establish itself into the forest ecosystem again, “Dobry said.

The American chestnut could bring other problems to the forest. In 2018, while working as an undergraduate researcher at LERGREC, Dobry discovered a fungus that was atypical for the American chestnut species.

“Initially, we assumed this was an unusual presentation of chestnut blight infection,” she said, “but after taking samples and doing research, we did not find , but a pathogen commonly known as chestnut brown rot. At the time, there had been no published report of this fungus in our hemisphere.”

Dobry continues to study the domestically isolated strain, examining whether it may be harmful to species of trees closely related to the chestnut, such as oaks.

“If this proves pathogenic to oak, it could be another blow to dynamics,” she said. “That’s why the chestnut project and others like it are so important to protect the diversity and future of our forests.”

Researchers identify new threat to American chestnut trees (2021, October 25)
retrieved 25 October 202

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Hexbyte Glen Cove Lemon trees showed less response to citrus greening disease pathogen than orange trees thumbnail

Hexbyte Glen Cove Lemon trees showed less response to citrus greening disease pathogen than orange trees

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Credit: CC0 Public Domain

Citrus greening disease was first discovered in Florida in 2005. Since then, production of oranges in the United States for processing has declined by 72 percent between the 2007-2008 growing season and the 2017-2018 growing season, primarily in Florida. The disease was discovered in California in 2012, and now the state is beginning to see a rapid increase of citrus greening disease.

As there is currently no cure for citrus greening disease, many growers are concerned about its rapid spread and many plant pathologists are focused on learning more about the complicated nature of this disease. To add to this growing body of knowledge about citrus greening disease, a group of scientists working in California, New York, and Washington compared the early responses of two , Lisbon lemon and Washington navel orange trees, to infection by Liberibacter asiaticus, the pathogen that causes citrus greening disease.

These scientists conducted a comprehensive molecular analysis that showed that Lisbon lemon trees had less of a molecular response to the pathogen than Washington navel orange trees. In part, this might be because leaves of infected lemons tended to accumulate micronutrients, which led to less of an impact on photosynthesis. Additionally, , important for plant defense, were upregulated in lemons.

“These results may be important for developing varieties of citrus that are more tolerant or perhaps resistant to the HLB pathogen,” said Carolyn Slupsky, a UC Davis-based systems biologist involved with the research. “Our research highlights some key features that differentiate more tolerant from more susceptible varieties of citrus and may be used to develop new cultivars that are resistant to the effects of this pathogen.”

This study is the first to analyze the impact of the pathogen on citrus metabolism prior to symptom development. “Understanding early response is important,” added Slupsky. “As it may also help in developing technologies to detect the disease earlier.”

More information:
Elizabeth L. Chin et al, Multi-omics Comparison Reveals Landscape of Citrus limon and Citrus sinensis Response to ‘Candidatus Liberibacter asiaticus’, PhytoFrontiers (2021). DOI: 10.1094/PHYTOFR-09-20-0018-R

Provided by
American Phytopathological Society

Lemon trees showed less response to citrus greening disease pathogen than orange trees (2021, May 12)
retrieved 13 May 2021
from https://phys.org/news/2021-05-lemon-trees-response-citrus-greening.html

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Hexbyte Glen Cove More trees do not always create a cooler planet, geographer finds thumbnail

Hexbyte Glen Cove More trees do not always create a cooler planet, geographer finds

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Forest conversion from 1986 to 2000. Percentage of forest pixels converted, mapped at a 990 m x 990 m resolution. All cities with a population greater than 250,000 are displayed as black dots. Credit: Clark University Professor Christopher A. Williams

New research by Christopher A. Williams, an environmental scientist and professor in Clark University’s Graduate School of Geography, reveals that deforestation in the U.S. does not always cause planetary warming, as is commonly assumed; instead, in some places, it actually cools the planet. A peer-reviewed study by Williams and his team, “Climate Impacts of U.S. Forest Loss Span Net Warming to Net Cooling,” published today (Feb. 12) in Science Advances. The team’s discovery has important implications for policy and management efforts that are turning to forests to mitigate climate change.

It is well established that forests soak up from the air and store it in wood and soils, slowing the accumulation of greenhouse gases in the atmosphere; however, that is not their only effect on . Forests also tend to be darker than other surfaces, said Professor Williams, causing them to absorb more sunlight and retain heat, a process known as “the albedo effect.”

“We found that in some parts of the country like the Intermountain West, more forest actually leads to a hotter planet when we consider the full climate impacts from both and albedo effects,” said Professor Williams. It is important to consider the albedo effect of forests alongside their well-known carbon storage when aiming to cool the planet, he adds.

The research was funded by two grants from NASA’s Carbon Monitoring System. Williams and his research team—comprising data scientist Huan Gu, Ph.D. from The Climate Corporation and Tong Jiao, Ph.D.—found that for approximately one quarter of the country, forest loss causes a persistent net cooling because the albedo effect outweighs the carbon effect. They also discovered that loss of forests east of the Mississippi River and in Pacific Coast states caused planetary warming, while forest loss in the Intermountain and Rocky Mountain West tended to lead to a net cooling.

According to Professor Williams, scientists have known for some time that expanding forest cover cannot be assumed to cool the planet or to mitigate global warming. However, this has not always been appreciated broadly.

“If we fail to consider both the carbon and the albedo effects, large-scale tree-planting initiatives, such as Canada’s 2Billion Trees Initiative and The Nature Conservancy’s Plant a Billion Trees campaign, could end up placing trees in locations that are counterproductive for cooling the climate system,” said Professor Williams.

“It is all about putting the right trees in the right place,” said Williams, “and studies like ours can help identify where the potential for cooling is greatest.”

Every year, approximately one million acres of forest are being converted to non-forest areas across the lower 48 states of the U.S.; this is largely due to suburban and exurban expansion and development. Professor Williams’ team found that the net climate impact of a full 15 years of forest losses amounts to about 17% of a single year of U.S. fossil fuel emissions.

Clark University Professor Christopher A. Williams. Credit: Photographer Steven King

Williams’ research team used state-of-the-art satellite remote sensing to bring a detailed, observational perspective to examine this problem that had previously been assessed mostly with computer models. The three researchers pinpointed the locations of forest loss and identified what those sites became—urban, agricultural, grassland, shrubland, pasture, or something else. They then quantified how much biomass carbon was released to the atmosphere, and how much additional sunlight was reflected out to space. By comparing these two effects they measured the net impact of deforestation on the climate system.

The new datasets and methods used in Professor Williams’ study show that the tools are available to take the albedo effect into account. The Clark team hopes to generate actionable datasets to share with land managers and policymakers worldwide within the next one or two years, to help ensure that their tree-planting efforts focus on the right places and have the intended effects.

More information:
“Climate impacts of U.S. forest loss span net warming to net cooling” Science Advances (2021). advances.sciencemag.org/lookup … .1126/sciadv.aax8859

Provided by
Clark University

More trees do not always create a cooler planet, geographer finds (2021, February 12)
retrieved 14 February 2021
from https://phys.org/news/2021-02-trees-cooler-planet-geographer.html

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