By Krissy Waite
For the past nine years, Paula Turkon, assistant professor in the Department of Environmental Studies and Sciences at Ithaca College, has been working on creating a timeline that can be used to date environmental and cultural changes in Northwestern Mexico using trees.
“The work that we’re doing is still preliminary,” Turkon said. “We’re building what we call a master sequence, and that can then be used to interpret things, but the construction of it is slow work because we don’t have anything to compare it to.”
Turkon’s research, “Chronology, Climate, and Culture in Prehispanic Mesoamerica: Contribution of Tree-Ring Studies,” aims to understand climate events — like droughts and heavy rainfall periods — and cultural changes in Northwestern Mexico using dendrochronology, or the study of tree rings. She said she became interested in this region when she was invited by her graduate school adviser to work there. Once there, she said, she wondered how people lived and produced food in such a dry environment.
The research is funded through a grant from the National Science Foundation. Turkon also works through Cornell University’s Tree-Ring Laboratory. She also works closely with colleagues at the National Institute of Forestry, Agricultural and Livestock Research and the National Institute of Anthropology and History in Mexico.
Turkon said her original research focused on understanding the degree to which people in this region were dependent on agriculture, which correlates with the amount of rainfall in the desert. She said she had trouble answering questions related to how agricultural and cultural changes happened because the data she had to reference were food remains, which are hard to put a date on. She said she also wondered if the variability of rainfall in the arid area was a factor in the past. She said she thought she could answer both questions using dendrochronology.
Dendrochronology is a technique in which the annual growth rings in trees, commonly known as tree rings, are studied to date events and environmental changes. Turkon said rainfall is the biggest factor that generally affects tree growth in the areas in Mexico where she takes samples. This means that a bigger, thicker tree ring could indicate a good rainfall year and a thinner tree ring could indicate a bad rainfall year. In Northern Mexico, it rains between 9.2 and 26.2 inches per year. Other factors, like the tree’s species, can also affect tree ring growth. Turkon said this technique has not been applied in this region of Mexico before.
By Alissa Walker
On Dallas’s hottest summer days, Matt Grubisich would dispatch his colleagues at the Texas Trees Foundation to take manual air temperature readings across the city. “You think the number to go by is the weather station out at the airport,” he says, pointing to Dallas’s Love Field, five miles northwest of the city center. “But then we’d go to a parking lot downtown where it was 6 degrees warmer.”
As the director of operations and urban forestry for the Texas Trees Foundation, Grubisich was trying to demonstrate that Dallas needed to make major design changes to fortify itself against epic heat waves. “It’s easy to explain to people why they park under a tree when they drive to the grocery store,” he says. Getting local leaders and the population at large to take action to bring more trees to the city was a tougher sell.
Thanks to the city’s 2015 effort to map its urban forest, Grubisich and his team already knew that the city’s trees were not evenly distributed. Almost half of Dallas’s trees were located within the Great Trinity Forest, a 6,000-acre nature preserve. That didn’t leave a lot of trees for the rest of the city, where some neighborhoods only had tree canopy over 10 percent of their communities.
To make the case for rethinking the city’s approach to trees, Grubisich and the Texas Trees Foundation turned to data on a larger scale. The organization’s comprehensive urban heat study, released in 2017, showed that one-third of the city was suffering from a phenomenon called urban heat island effect. A full 35 percent of the city was covered by impermeable surfaces, like parking lots, roads, and buildings, which absorb sunlight and end up heating up the air around them.
“I knew we would have a rather robust urban heat island,” says Grubisich. “That number, that was the most alarming part. That was the catalyst.”
Dallas’s heat island was more than robust: Parts of the city were up to 15 degrees Fahrenheit warmer than their rural counterparts. The urban heat island was expanding so rapidly that the ninth-largest city in the country was warming faster than any other large U.S. city except Phoenix.
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.”
After a record low winter run-off, some water experts are now calling this Arizona’s worst mega-drought in recorded history, even when compared to tree-ring data that goes all the way back to the 1300s.
By Scott Miller
New insights into the impact forests have on surface temperature will provide a valuable tool in efforts to mitigate climate change, according to a new research paper co-authored by Clemson University scientist Thomas O’Halloran.
For the first time, scientists have created a global map measuring the cooling effect forests have by regulating the exchange of water and energy between the Earth’s surface and the atmosphere. In many locations, this cooling effect works in concert with forests’ absorption of carbon dioxide. By coupling information from satellites with local data from sensors mounted to research towers extending high above tree canopies, O’Halloran and his collaborators throughout the world have given a much more complete, diagnostic view of the roles forests play in regulating climate.
Their findings have important implications for how and where different types of land cover can be used to mitigate climate change with forest protection programs and data-driven land-use policies. Results of their study were recently published in the journal Nature Climate Change.
Rudy Boonstra has been doing field research in Canada’s north for more than 40 years.
Working mostly out of the Arctic Institute’s Kluane Lake Research Station in Yukon, the U of T Scarborough Biology Professor has become intimately familiar with Canada’s vast and unique boreal forest ecosystem.But it was during a trip to Finland in the mid-1990s to help a colleague with field research that he began to think long and hard about why the boreal forest there differed so dramatically from its Canadian cousin. This difference was crystallized by follow-up trips to Norway.”Superficially they look the same. Both are dominated by coniferous trees with similar low density deciduous trees like aspen. But that’s where the similarities end,” he says.The real differences are most obvious on the ground, notes Boonstra. In Canada, the ground is dominated by tall shrubs like willow and birch but in the Northwestern European forests found in Norway, Finland and Sweden the ground is dominated by dwarf shrubs like bilberry.
Major forest die-offs due to drought, heat and beetle infestations or deforestation could have consequences far beyond the local landscape.
Wiping out an entire forest can have significant effects on global climate patterns and alter vegetation on the other side of the world, according to a study led by the University of Washington and published Nov. 16 in PLOS ONE.
“When trees die in one place, it can be good or bad for plants elsewhere, because it causes changes in one place that can ricochet to shift climate in another place,” said lead author Elizabeth Garcia, a UW postdoctoral researcher in atmospheric sciences. “The atmosphere provides the connection.”
Read more at: http://phys.org/news/2016-11-large-forest-die-offs-effects-ricochet.html#jCp