September 23, 2011
You may have noticed people on the streets of Delaware holding PDAs and measuring street trees. The data collection is being done by the Delaware County Master Gardener Volunteers as part of a project to inventory all the street trees in the City of Delaware.
Pam Bennett is the Ohio Master Gardener Coordinator and a strong advocate of the street trees project. She says that Master Gardeners have been involved in more than 15 street tree inventories at various locations across the state, including Springfield in Clark County where Pam is also an OSU extension agent. She sees these efforts as a way to implement the Master Gardener’s environmental horticulture initiative and the projects tie in directly with OSU’s focus on “Why Trees Matter.”
The Street Tree Commission in the City of Delaware is comprised of nine volunteers. It is the governing body that oversees the street trees. According to Chuck Rexrode, a retired USFS research entomologist who has worked as Delaware’s contract forester for more than 20 years, there are more than 12,000 street trees in the City of Delaware. This includes nearly 2,800 trees in the center of the city. New developments, which sprang up during what Chuck calls the “Golden Age” (between 1995 and 2005) account for about 10,000 trees. In total, Delaware’s trees are valued at about $15 million, with many of the most mature and valuable specimens located in the central city.
According to David Carey, who serves on the city’s Shade Tree Commission, “the tree inventory raises public awareness, helps keep tabs on the trees, and helps with planning.” He adds that electronic records will provide the continuity necessary for the successful implementation of the city’s long-term street tree maintenance program, which has been cut back in recent years due to budget constraints.
To help facilitate the street tree inventory project, Davis Sydnor, Professor of Environment and Natural Resources, and Sakthi Subburayalu, a research associate in the School of Environment and Natural Resources, provided background on the project and the process. Sakthi also customized i-Trees software package for the Delaware County Master Gardeners who are doing the data collection. The City of Delaware Information Technology Department provides detailed section maps.
Master Gardeners, spearheaded by veteran Master Gardener Susan Logan, use PDAs to record several attributes for each tree, including the street address, GPS coordinates, tree species, and its diameter at breast height (DBH). This data is uploaded to a computer. The information is also sent to a database maintained by The Ohio State University for use by their research staff. i-Trees software utilizes a model that quantifies the benefits of a tree using the species and DBH to get an idea of the canopy volume. In addition to the beauty and enhanced property value trees offer, i-Trees calculates the savings from an energy standpoint, storm water mitigation, air pollution benefits and carbon capture or sequestration.
Sakthi has coauthored several reports analyzing the street tree data already collected in four Ohio communities, Westerville, Dublin, Toledo and Yellow Springs. According to him, the studies have shown that most of their trees are smaller in order to accommodate being under power lines. Conversely, from an environmental impact viewpoint, he notes that we need larger trees. Chuck Rexrode agrees with his analysis. He says that trees that mature at a relatively short height are planted to avoid “topping” by power companies that can disfigure the tree. The Tarterian and Trident maples are two trees that only grow to 18 feet and fit well under high voltage wires. However, because the city code requires that branches have 8 feet clearance over the sidewalk and 14 feet clearance over the street, that leaves a negligible tree canopy. While Japanese lilac trees and serviceberries are two other trees that Chuck recommends for planting under power lines, he also notes that they prefer afternoon shade.
University research has also found that diversity at the cultivar and species levels are generally good. However, according to Sakthi, at the genus (family) level, the diversity is lower. For instance, in Toledo, 50 percent of the street trees are maples. This could be a problem, since pests generally are not limited to one cultivar or species, but attack all the trees in the same genus. The Asian Longhorned Beetle (ALB) is a newly identified pest in Ohio. It has been found near Cincinnati and is known to attack maple trees. With half of the street trees in Toledo being maples, according to Sakthi, that city could face a major problem, if the pest is not controlled and attacks Toledo’s trees. Chuck estimates that 30 percent of the trees in the City of Delaware are maples.
The Emerald Ash Borer (EAB) has hit the large majority of the ash trees in the City of Delaware since it was first identified in the city in 2006. According to Chuck, there were 1,546 ash trees in the city five years ago. After the city completes the planned removal of 397 trees this winter, only 284 ash trees will remain and more than 90 percent of those trees are already infested with EAB. David Tidd, the former Parks & Urban Forestry Division Supervisor for the City of Delaware, applied for a cost-shared grant for ash tree replacement that enabled the city to replace 100 trees in 2011. However, only 129, or about 10 percent, of the 1,262 ash trees that have been removed have been replaced.
EAB has already cost the city about $1 million and the total cost is expected to reach $1.3 million before the EAB is completely eliminated from the local street trees.
Dave Carey is proud of how “the City, the Street Tree Commission, OSU extension, and the OSU Department of Forestry are working together to get this done, and it’s not costing the city anything.“ His goal is ultimately to have the street tree database accessible to the public, so they can know the value of their trees.
Nancy F. Traub is an OSU Extension Master Gardener volunteer.