Greg Shriver, assistant professor of wildlife ecology in the Department of Entomology and Wildlife Ecology and research scientist with the Center for Managed Ecosystems at the University of Delaware, is collaborating with the U.S. Forest Service to continue work on a project that focuses on assessing the conditions of urban forests and explores ways in which to improve those conditions.
The project is known as Forest Fragments in Managed Ecosystems, or FRAME, and it has its origins in a study titled “Wildlife Ecology and Urban Impact” conducted 45 years ago at UD by scientists in the Department of Entomology and Wildlife Ecology and the Forest Service.
The 1965 study was continued by Roland Roth, UD professor emeritus of wildlife ecology, beginning in 1972. Although Roth could not have known at the time, Shriver said that his work — conducted on the UD Farm — became the longest running study on the demographics of the wood thrush, a neotropical migratory bird.
Shriver, who subsequently picked up the mantle, called the wood thrush the “hallmark species” for this research and said FRAME builds on Roth’s earlier studies. The FRAME project was initiated as a collaborative effort between Shriver; Vincent D’Amico, a Forest Service scientist stationed at UD; Jake Bowman, associate professor of entomology and wildlife ecology; and Jeff Buler, assistant professor of entomology and wildlife ecology.
Shriver said FRAME is “a fairly large-scale forest fragmentation study aimed at assessing the condition of urban forest fragments to see if we can increase their quality.”
These forest patches dotting the developed landscape “are providing the some of the only remaining habitat for neotropical migratory birds, small mammals, and insects,” he said.
The group is currently establishing long-term plots and surveying the condition of Mid-Atlantic forest fragments.
After assessing the overall health of the forest fragments, Shriver said he and his colleagues will research ways to improve them. “The big picture is that these fragments are providing important ecosystem services — air, water, things required to make the area livable,” he said. “The goal of the FRAME project is to better understand the interactions between soil, water, plants and the animals dependent on them within urban and suburban environments.”
Shriver, who will be aided by graduate students, said the study will be multifaceted, with the first part focusing on multitrophic effects of soil acidification and biodiversity.
“There has been some concern that acidification in soils, especially here in the Northeast, could be limiting the availability of calcium-rich prey — such as snails and isopods — that birds need during the breeding season to make eggshells and feed their nestlings, because the nestlings’ growth rate is so fast and they need so much calcium,” Shriver said. “Studies have shown that if you have limited calcium availability, you have limited calcium-rich prey, which then limits the breeding density and reproductive success of some bird species.”
The FRAME study has broken the Newark area’s urban forest fragments into grids using GPS systems, starting with the original study patch from the Roth study and adding 19 other woodlots.
In each of the fragments, Shriver said he and his students plan to “estimate breeding bird territory density, nest survival, a measure of reproductive success, and species diversity. We’re also taking soil samples and then litter samples to see if we can link the soil pH to calcium-rich prey.”
Shriver explained that a low pH means that the soil has a high amount of acidification, and that “the acidification comes mostly from acid rain, which has been greatly reduced since the height of the Industrial Revolution, but the soils have likely not recovered. Once you push a soil into an acidic state, unless it has some buffering capacity, it is very hard to get it back.”
What happens with soil that has been pushed to an acidic state, he said, is a reduction in calcium-rich prey, which in turn limits food for breeding birds. The birds either have lowered reproductive success or leave that forest fragment.
The first two years of the FRAME study are dedicated to gathering the pre-data, showing the present condition of the soil. Shriver said the research team then plans to “lime the forest patches to see if we can increase their quality, which will raise the pH and release the calcium,” thereby improving biodiversity.
They plan to treat 10 sites with lime and leave another 10 sites untreated in order to compare differences in soil quality. He said he is confident that “changing the pH is going to change a lot to these forest fragments.”
The research team is partnering with the Newark Department of Parks and Recreation, New Castle County Parks, and Delaware State Parks. Shriver said that “without the cooperation and enthusiasm we’ve received from all the partners, this project would not be possible.”
Shriver received a bachelor of science degree in wildlife management from the University of Maine, a master’s degree in wildlife conservation from the University of Massachusetts and a doctorate in environmental forest biology from the State University of New York (SUNY). He joined the UD faculty in 2005.