Earth, Wind, and Fire
Last month was all about water, and in April we focus on the other three elements: Earth, wind and fire. Meet a scientist who is fascinated by the traces of past forests that remain on the landscape; learn about a study that delivered an unexpected lesson on fire ecology, and see why a partnership is recommending that some trees uprooted by wind should be left on the forest floor.
Last winter, while collecting field data, Research Ecologist Todd Hutchinson came across a tree species that he could not immediately identify. For a scientist, encountering a puzzling tree is like being handed a plate of birthday cake when it isn’t your birthday. The icing on that cake was that Hutchinson was able to identify the tree, and the tree was a healthy blue ash, making it potentially useful to a colleague’s work in breeding ash for resistance to emerald ash borer.
As a research ecologist, Hutchinson has many opportunities to be in the woods with projects exploring fire ecology, forest regeneration, and the complicated world of Ohio’s oak forests. One of Hutchinson’s favorite studies involved work that began in the 1990s and seemed to have unexciting results – low intensity prescribed fire resulted in oak seedlings sprouting, but they failed to grow into larger sized trees. What made the study exciting was the unexpected death of some large white oaks within the research plot, caused by caterpillar defoliation and other factors. In the resulting canopy gaps, oak seedlings grew quickly into larger sizes, a development that demonstrated that openings in the forest canopy, coupled with prescribed fire, can assist in oak regeneration success.
Hutchinson is fascinated by the glimpses of forests past that remain on the landscape. His research has included using “witness trees,” which were noted in original surveyor’s notes from more than 200 years ago. “Forests always make me think about what happened here in the past, why do we have this mix of species?” Hutchinson said.
Over the course of his career, technology has had a profound effect on research, Hutchinson said. Finding literature on topics he is studying no longer requires hours spent in a library, and computer processing has advanced, making it possible for scientists to conduct statistical analysis on large landscapes rather than just a single stand of trees.
Just as the technology he uses has evolved, Hutchinson’s perspective on forests has also evolved. “My ecological education focused on natural processes in forests, but I have learned that today’s forests almost always need active management to favor desired species and other conditions,” Hutchinson said.
More about Todd Hutchinson >>
1 fire, 2 trees
Following a prescribed fire on the Monongahela National Forest in West Virginia, trees both dead and alive were chosen for a demonstration of fire effects on large trees harvested for timber.
Prescribed fire is one tool used to clear the mid-story and litter layer in oak forests to encourage oak seedling growth, however landowners are concerned about damage to residual trees headed for the sawmill. Researchers used a portable sawmill to cut the logs into boards to see how far fire damage penetrated, if at all. A look at a chestnut oak and a northern red oak treated scientists to an impromptu lesson in fire ecology
In fire ecology terms, chestnut oaks have more fire-adapted traits than northern red oaks. These traits include thick bark to protect the living part of the trunk. But in this case, the chestnut oak died after the fire, and the northern red oak survived. In both trees penetration of fire damage was minimal, so the value of the timber was not reduced.
Closer examination of the two trees showed that the chestnut oak trunk was charred up to 10 feet high, while the northern red oak was only charred up to 3 feet. The crew that harvested the trees shared that the chestnut oak had been growing in a patch of tall, dense mountain laurel which has flammable evergreen leaves, while the northern red oak grew on a moister spot not surrounded by shrubs.
“Despite its fire adaptation, the chestnut oak was killed due to conditions in its immediate surroundings that caused a hotter fire,” said Melissa Thomas Van-Gundy, research forester based in Parsons, WV. “Species are adapted to a fire regime, rather than a particular fire. In this case the chestnut oak lost out.”
Leaving It Messy: How Tip-Up Mounds Promote Tree Species Diversity
If a tree falls in a forest and no one is around to hear it, does it make a sound? While this question may be left to the philosophers, Northern Research Station (NRS) scientists, in collaboration with the State of Wisconsin Board of Commissioners of Public Lands (BCPL) are investigating a somewhat similar question: If a tree falls in a forest, and someone is around, should it be removed? In managed forests, common practices call for cleaning up and removing timber following a blowdown, however new research suggests that leaving downed trees may be a key component to boosting tree species diversity in northern hardwood forest communities.
In forests affected by moderate-severity windstorms, uprooted trees and exposed root masses turn into what are known as tip-up mounds. Over time, these exposed root structures create microtopography, or slight elevational variations in the forest that can serve as habitat for a variety of tree species.
Christel Kern, NRS Research Forester, John Schwarzmann, Board of Commissioners of Public Lands Forest Supervisor, and others are looking into how tip-up mounds affect overall tree species diversity. They found that as these mounds decay and saplings begin to grow on them, their height relative to the main forest floor provides some protection from animal browsing. That means that certain tree species, especially those that are “light-seeded” – with seeds that are blown by the wind – have advantages to regenerate if some mounds are left intact.
As Kern describes it, “Nature can look messy after a blowdown, but there are unique opportunities that can lead to diversification that lasts for hundreds of years.”
“Management practices following blowdown events usually involve salvaging the largest, most valuable trees,” said Schwarzmann. “Following a blowdown event, we suggest salvage areas leave a portion of uprooted trees un-salvaged and protected from heavy equipment traffic to maintain newly created mounds.”
Schwarzmann said the study findings may help guide forest managers across the region who are interested in supporting management practices that can maintain difficult to regenerate tree species by paying attention to natural disturbances. “Even if the mounds are lower than you’d expect to make a difference,” he says, “a moderate blowdown may be the only chance in the lifetime of a stand to enable regeneration of browse-sensitive tree species.”