Mighty oak trees not thriving in Ohio

COLUMBUS – One way to keep the mighty oak from losing its dominance in Ohio forests may entail bringing back an old friend that made possible its survival and expansion for thousands of years: fire.
Burning project. A collaborative research project between Ohio State University and the Ohio Department of Natural Resources is looking at the effects of prescribed burns and shelterwood cutting (a type of selective clearing) on southern Ohio forests, which have traditionally been dominated by oak, but are increasingly losing ground to other hardwood species such as maple, yellow poplar and blackgum.
The project also includes a first-of-its-kind study aimed at determining the impact such management techniques may have on bats, which respond very quickly to changes in their environment and are an important indicator of biological diversity.
Oaks not making it. “You go to these forests and you find oak seedlings in the understory, but they are not making it,” said Roger Williams, an associate professor of forestry with the School of Natural Resources in Ohio State’s College of Food, Agricultural, and Environmental Sciences.
“Oaks need light, so other species that are shade-resistant, such as maples, are winning the battle on the forest floor.”
Oak species have been a key component of deciduous forests in Ohio and the eastern United States for some 10,000 years.
Good for environment. Today, oak forests occupy 59 percent of forestland in the Buckeye state – protecting soil and water resources, supporting numerous plant and animal communities, and providing food to wildlife through their massive production of acorns.
However, the number of oaks has been dwindling during the past 80 years. Why?
Williams said the onset of aggressive forest-fire suppression programs in the United States in the early 1900s, while doing a great deal to protect forest resources to date, may be to blame.
Forestry-fire programs. Before the time of Smokey the Bear, periodic fires were common across the forest landscape. This favored the regeneration and growth of oaks, which are fire tolerant, over fire-intolerant species such red maple and American beech.
Fires helped open up the canopy, which further helped the light-loving oaks to prosper and dominate the forest. With fires gone, oaks have lost their competitive advantage.
Andy Ware, assistant chief of ODNR’s Division of Forestry, said the five-year study – which began this fall at Richland Furnace and Zaleski State Forests – is key to determining appropriate management options to sustain Ohio’s natural resources over time, as both forest ecosystems and the state’s forest industry can be impacted due to oak decline.
About the study. The study is being conducted on 100 acres, divided into five 20-acre treatment sites. One of the sites is a control, which means no cutting or burning will be done there – this plot is used only to compare it to those being altered.
Shelterwood cutting, which already took place, was conducted using low-impact equipment to minimize damage to the ground, Ware said.
“We are looking at different ways of disturbance to help (oaks) become predominant again,” explained Williams, also a scientist with the university’s Ohio Agricultural Research and Development Center.
“We started with shelterwood cutting, which involves a reduction in canopy cover by performing a low thinning.
“In two of the sites we removed 50 percent of the canopy, while in the other two sites we removed 30 percent. Within three years we will conduct prescribed burns, combining both spring and fall burns.”
Initial cut is key. Williams said the initial cut of any shelterwood treatment is critical to the overall success of oak-regeneration efforts, as it makes light available to oak seedlings.
However, there’s no consensus as to the recommended cutting intensity required to achieve better results. That’s why this study is looking at both high and low clearing percentages.
Likewise, Williams said, it’s important to determine the efficacy of both spring and fall prescribed fires.
When to burn. Spring burns are recommended in the area because the best fuel and weather conditions needed to achieve hot fires occur during this time of the year. But in southern Ohio, the window of opportunity for spring burning is narrow, so forest managers need to have flexibility when applying prescribed fires.
The second aspect of the project involves monitoring bat populations to assess the effect – positive or negative – that shelterwood cutting, burning or both could have on the flying mammals.
Impact on bats. “Little or no research has been conducted on the impact of wildfire and prescribed burning on bats and bat populations,” said Stan Gehrt, a wildlife specialist with Ohio State University Extension.
“Ohio bats either migrate or hibernate from late fall to spring, and most are probably not using forests during the time burns are conducted; therefore, fire likely has little direct effect on individual bats.
On the contrary, reducing the canopy density may actually help bats, as they prefer to forage in open areas with less tree clutter. There’s evidence that bats like to roost in oak species, so regenerating these forests could be beneficial to them.”
Engaging in management practices that promote a diverse bat population is important for forest sustainability, Gehrt said.
In addition to being a good indicator of biological diversity – a decline in bat numbers “tells us there’s something wrong in a particular ecosystem,” he pointed out.
Bats not all bad. Bats are the main predator of nocturnal, flying insects, many of which are considered agricultural pests or threats to human health, such as mosquitoes.
Bats may also play an important role as “nutrient pepper shakers” in forest ecosystems. Because of the energy needed to fly, some bats can eat as much as 100 percent of their body weight each night.
And everywhere bats fly, they also poop – dispersing nitrogen-rich feces across considerable distances and bringing this valuable cargo to their roosting sites, which are often located in relatively nutrient-poor areas of the forest.
Tracking bats. To determine the distribution and activity of different bat species during the study, researchers will record their distinctive calls with broadband ultrasonic bat detectors from June to September.
“Mist” netting is also used to gently trap bats as part of the study.
“Prescribed fire is probably going to become a more common forest management practice, so it’s important that we learn as much as possible about its impact on different species and on other aspects of the forest ecosystem,” Gehrt said.
Nothing new. ODNR has run a prescribed fire program in the state since the early 1980s to address various management issues.
In 2004, some 25,000 acres were burnt under this program in both public and private woodlands.