The Holden Arboretum Research Plots
by
Sarah Pawlaczyk, Katelyn DeFranco, Jay Hillery, and Alex Cameron
On April 26th, 2015 we visited The Holden Arboretum, Kirtland Ohio. The Holden Arboretum is a private institution dedicated primarily to collecting trees but is also home to many different shrubs, herbaceous plants, and animal species. We met up with Research Scientist Dr. David Burke to visit an active research plot where Holden’s scientists are currently conducting experiments on. Dr. Burke is an ecologist who is interested in the interactions between plants and soil microorganisms, more specifically the mutualistic relationships that form between fungi and roots. Holden Arboretum offers a unique opportunity as a study system as it is one of the finest stands of mature beech – maple forests in Ohio.
We hiked up to a site in the Pearson Creek Valley watershed, one of the cleanest watersheds in the region, which is with 90% almost exclusively owned by the Arboretum. The plots we visited were involved in a project that the Holden scientists received NSF funding to examine acidic precipitation and forest health. It is a long-term study looking at how forest soils respond to changes in acidity and availability of phosphorus. In one experimental treatment the scientists spread crushed limestone to manipulate the pH and in another phosphorus fertilizer or both to see how the plants and soil microbe communities respond.
We hiked up to a site in the Pearson Creek Valley watershed, one of the cleanest watersheds in the region, which is with 90% almost exclusively owned by the Arboretum. The plots we visited were involved in a project that the Holden scientists received NSF funding to examine acidic precipitation and forest health. It is a long-term study looking at how forest soils respond to changes in acidity and availability of phosphorus. In one experimental treatment the scientists spread crushed limestone to manipulate the pH and in another phosphorus fertilizer or both to see how the plants and soil microbe communities respond.
One question the scientists were interested in are the feedbacks of the treatments to the carbon and nutrient cycling of the trees and herbaceous plants, in specifically growth and production. We saw that within each plot trees were tagged and learned that the scientists measure the tree diameter at breast height yearly to see how much the trees are growing in girth. Dr. Burke demonstrated the sophisticated sling-shot that is used to sample leaves from tree canopies in different times throughout the season to sample their tissue content.
The scientists are also investigating the impacts of pH changes on the mycorrhizae communities living in the soil. Mycorrhizae are fungal communities that have a mutualistic relationship with the trees. Dr. Burke showed us how one can detect these mycorrhizae by driving a core into the soil near a large tree. The fungi of interest are generally found on surface roots of trees that are thin and shallow in the soil very close beneath the ground. After pulling the core out and brushing off the soil we were able to see this very tiny extensions on the root, similar to small hairs. Dr. Burke explained how we can identify morphotypes of mycorrhizae. For example, some mycorrhizal infections of roots can appear yellow, brown, or white. However, the only way to identify these fungi to species level is to use molecular techniques. We learned that these interesting communities even change throughout the year, for example, the communities found in May can be very different to those one can find in July and August. Fascinating was that there are even some plants such as the ghost plant, that are parasitic to the mycorrhizae robbing carbon and nutrients from the mycorrhizae and his host tree.
After hiking back, Dr. Burke was kind enough to show us around the research facility which included a state of art DNA lab, multiple greenhouses, a lab for plant tissue analysis including a newly acquired machine that calculates leaf area.