September 15, 2009

By Isabel Sterne

It wasn’t exactly a walk in the woods but College of Agriculture and Life Sciences’ students Christian Gruber and Fred Cowett spent several weeks this past summer counting and measuring trees on the Cornell campus as part of the university’s Climate Action Plan.

During the summer Gruber and Cowett conducted the first-ever campus tree survey, which was sponsored by the Cornell University Agricultural Experiment Station (CUAES). Over the course of two weeks, the students identified and measured 7,200 trees on the 2400-acre Cornell campus.

“We really got to see every nook and cranny this campus has to offer,” says Gruber, a graduate student in landscape architecture.

Cornell's first comprehensive tree inventory identified 300 species on campus--from a 350-year-old white oak to a 80-inch-in-diameter pignut hickory--that collectively store 15 millions of pounds of carbon and annually provide more than half a million dollars in "ecosystems benefits" to the university. The ecosystem benefits were calculated with a software program, STRATUM, developed by the USDA Forest Service that estimates the value of energy savings, storm water mitigation and carbon sequestration, among other things.

Using aerial photographs from 2007 and a handheld GPS unit, Gruber and Cowett noted the species and trunk diameter for every tree on campus, with the exception of trees at Cornell Plantations and in naturally wild areas such as the gorges.

“The on-campus tree life at Cornell is interesting because of its diversity, including a large population of oaks, which is somewhat unusual since maples are the most common genus of street trees in New York,” says Cowett, a graduate student in the horticulture department.

The tree inventory was entered into Cornell’s Geographic Information System (GIS), giving university landscape planners and facilities engineers the ability to incorporate tree diversity and forestry management plans into future university projects. Knowing what kind and how many trees are in a given area is valuable in planning everything from large building construction to smaller projects, like utility line installations and winter sidewalk salting, which have typically been the most harmful to campus trees in the past. Indeed, Gruber and Cowett discovered that approximately 200 trees on campus had died or been removed since the aerial photos were taken in 2007.  

“We needed to know what we have before we can manage it and put a value on it,” says Nina Bassuk, a professor in the Department of Horticulture and the project’s adviser. Bassuk said the tree inventory was a critical step in assessing Cornell trees’ “value,” as measured by such things as energy conservation, carbon sequestration, and runoff filtration. This information is also important for the university’s Climate Action Plan to achieve climate neutrality by 2050. According to the STRATUM computer model the replacement value for all of Cornell’s trees and the services they provide is more than $19 million.

On the basis of the tree inventory, Cornell is now a member the Arbor Day Foundation’s Tree Campus USA, which recognizes schools for excellence in effective forest management and student involvement in forestry efforts. The inventory showed that 24 percent of the campus is under canopy.

In addition to involving students in the tree survey, CALS offers several other opportunities to students interested in urban forestry. One example is a summer class run by Bassuk, known as SWAT, or the Student Weekend Arborist Team. As SWAT members, students work with communities in New York to help them inventory and develop “green” management plans. Both Gruber and Cowett are active members of SWAT and use the same practices for inventorying the trees on-campus as they do when they visit outside communities.

In another tree project this summer, CUAES planted 5,000 young saplings on a hillside to regenerate a forest at its Freeville Research farm, about 15 miles from campus. The side-hill planting is designed to sequester carbon with a mixture of soft and hardwoods, including oak, which, in the long term, offer more carbon sequestering capability than softer, faster-growing woods, such as pine. Once the newly planted trees are established, the five-acre hillside will not require mowing, saving energy and labor.