By Molly Day
Phoenix Correspondent
August 22, 2007 06:48 pm
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The role of trees and forests in daily life is invisible to most of us even though we have heard that trees clean the air, cool the Earth’s surface, contribute to ecological processes and beautify our communities.
For some forestry professionals, the role of trees and their health is a cause and a passion.
“I’m studying the anthropological effects on our forests,” said Ryan DeSantis, a Ph.D. student at Oklahoma State University. “There are plenty of unanswered ecological questions whose answers may be fundamental to humans living sustainably in the future.”
According to Dr. Steve Hallgren, an associate professor in the Department of Natural Resource Ecology and Management at Oklahoma State University in Stillwater, the field of forest ecology includes approximately 15,000 scientists and teachers worldwide who specialize in community, plant or landscape ecology. Hallgren is one of around 3,000 working in the United States.
Forests provide carbon cycling required for life on earth and forest ecologists, including DeSantis, are working to study the role of forests in order to preserve that critical function.
“Early in the life of a tree, its growth rings appear quite wide,” DeSantis said. “As a tree ages, its growth rings generally get more narrow, as it focuses more energy on other things.”
He said that according to some unpublished research, instead of becoming smaller, growth rings in mature trees have actually gotten wider. This could be attributed to increasing carbon dioxide levels in the environment, which is more evidence of anthropogenically-induced global climate change, or “global warming,” as the popular but incorrect phrase goes.
“Making slight changes in our lifestyle can go a long way toward building a more efficient society,” DeSantis said. “It’s exciting that we’re realizing these changes which can ultimately make the world a better place.”
DeSantis’ project focuses on the effects of fire exclusion and climate change on Oklahoma Cross Timbers forests. The Cross Timbers area is made up of tallgrass prairie, oak savanna, and oak forest, and is dominated by post oak and blackjack oak trees. (For a map of the Cross Timbers area go to: http://www.uark.edu/misc/xtimber/map/)
“In general, while fire frequency has fluctuated, more intense fires seem to be less frequent today,” DeSantis said. “And that has had an effect on vegetation. Just as some conifers are fire adapted, certain grasses and trees in the prairies and forests of Oklahoma need fire and have always had fire. When you take that fire away or even alter the historical intensity or frequency of that fire, it can make significant ecological changes.”
In Oklahoma forests DeSantis is studying the possible decline of blackjack oak. Previous studies indicate that decades ago, Oklahoma may have had a greater proportion of blackjack oak. While blackjack oak is less hardy than post oak, it may reproduce (through sprouting) much more prolifically than post oak following fire. Take away the fire and you may have less blackjack oak.
Native Americans traditionally burned large parts of the state but that doesn’t necessarily mean that there used to be more blackjack, simply that over the past two to three centuries, blackjack oak appears to have been more abundant.
“I am looking into whether more frequent fires stimulate blackjack oak to sprout more,” DeSantis said. “Fire exclusion may ultimately suppress blackjack oak and encourage post oak.”
In the 1950s, Elroy Rice and William Penfound completed a survey of Oklahoma’s upland forests. DeSantis is relocating Rice and Penfound’s research areas and resurveying them. While the study is not yet complete it appears that Oklahoma’s Cross Timbers forests have more red cedar and post oak and less blackjack than they did more than 50 years ago.
DeSantis also said some conifers have dead branches as an adaptation to fire. Their dead branches serve as ladder fuels, which carry fire into the tree canopy. Those retained dead branches also fall off eventually and provide fuel for ground fires.
“Blackjack oak is the only deciduous tree I’ve ever seen that exhibits that same trait of retaining dead branches to that extent,” DeSantis said.
“Red cedar is expanding into rangelands as well as forests because of fire exclusion,” DeSantis said. “Also, when you do not have fire, dead material accumulates in forests and trees like blackjack oak die because they cannot out-compete other species. In effect, if blackjack oak does sprout prolifically following fire, fire could be blackjack oak’s only real competitive advantage.”
We know that trees remove carbon dioxide from the air through photosynthesis and we know that more CO2 is going into the environment due to increased car emissions.
“Animals also exhale CO2,” he said. “It is important to understand the process and how we are impacting the natural balance of the Earth’s atmosphere. By looking at tree rings, we can draw conclusions as to what effect our automobiles could have on this planet.”
After earning a bachelor’s degree, DeSantis served as a U.S. Peace Corps ecological volunteer for two years in Bulgaria where he worked with a local branch of Bulgaria’s forest service to help plant trees in the town he lived in.
“Local goats were left to wander and ate the young trees,” DeSantis said. “The next year we worked harder at the project and put wire mesh around the trees after they were planted. First the wire was stolen and then the goats ate the trees. It was frustrating at the time but I can’t help but laugh when I think about it now.”
After the Peace Corps, DeSantis earned a master’s degree in applied ecology in Michigan, worked at Cape Cod National Seashore and Grand Teton National Park. When he finishes his doctoral project, he hopes to teach and work at making our world a better place for future generations.
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