Exotic Trees for Biodiversity?

How do naturally regenerated native and exotic tree species found on vacant land differ in terms of their ecological and economic value within the urban forest? 

In “shrinking cities”, prolonged population decline has resulted in the proliferation of minimally managed vacant land. This property type supports a significant proportion of the urban forest, which is typically regarded as a beneficial resource because of its ability to remove and store atmospheric carbon dioxide, reduce stormwater runoff, and mitigate the heat island effect, all while improving the aesthetics of the landscape and serving as habitat for wildlife. In many cases, however, the trees that establish and make up the forest community found on vacant land are weedy, exotic species whose value to the urban ecosystem remains poorly understood. The goal of this research is to quantify and compare the value of the dominant native and exotic tree species on vacant land in order to better understand the value of these pockets of green space.

chris-group-photo

(photo: Chris and crew talking to a resident while in the field.)

How is this research conducted?

This research ultimately involves a number of smaller projects that have different questions and field methods behind them.

During 2015, trees found in a number of vacant lots and residential properties throughout the city were surveyed to collect information on the height and width of the canopy, the diameter of the trunk at breast height, and the percentage of the canopy that was missing or that had died back, among other measurements. A variety of tree measurement tools were used, including a clinometer and measurement tape. 

In 2016, insect communities found in a small number of focal tree species were sampled. Herbivorous and predatory insects found in the trees are being documented and what spiders are using the trees as habitat is being determined. Insects were being collected through a couple of approaches: some collected by striking branches and collecting what falls down, while others were collected in traps that were left in the trees for a week at a time.

Samples are collected in the following neighborhoods: Broadway-Slavic Village, Buckeye-Woodhill, Fairfax, and Glenville. Pocket Prairie treatments are not being utilized for this research project.

This project began in May, 2015 and the field component will resume each summer between May and August through 2018. Sampling windows will vary from year to year depending on the project and the exact methods being using.

What impact can this research have?

One of the major outcomes of this research will be an improved understanding of the ecology of the urban forest community found on vacant land. Understanding what tree species are present and how they are impacting the urban ecosystem can yield valuable information for natural resource managers and policy makers who have to consider a variety of factors when thinking about managing this growing property type. Results of this research may also spur a greater investment of resources in vacant lots as pockets of valuable green space, which would ultimately stand to benefit the residents who live in and around these sites.

This project is lead by Christopher Riley. Christopher studies Urban Forestry and Urban Ecology at the Ohio State University and is from Silver Spring, Maryland.

Christopher on the significance of this research:

“As more and more people come to view cities as a part of the solution to (vs. strictly the cause of) challenges such as habitat loss and climate change, there is an increasing need for research that seeks to target real-world issues through a combination of both basic and applied science. I am particularly drawn to the field of urban forestry because it provides me with an opportunity to address interesting and relevant ecological questions while also working to promote and conserve the tremendously valuable resource that is the urban forest. While most people think of urban trees as being primarily valuable for their aesthetic appeal or the shade they provide, they can also play a significant role in lowering energy costs, improving air and water quality, and serving as habitat for local wildlife, making their conservation a top priority.”


This material is based upon work supported by the National Science Foundation under Grant No. 1253197.

Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.