A Brief Survey of Campus Tree Inventories

Allees of elms and oaks lining Killian Court, the location of MIT’s annual commencement, will be designated a “Special Resource” area for a tree care program. / image: Laura Tenny

Does your campus have a comprehensive tree inventory, or has your firm been involved in inventory and management of campus tree canopy? This mini-series on The Field will highlight campus tree inventories among our Campus Planning & Design Professional Practice Network (PPN) group. This first post describes tree inventory at MIT; next in the series will be Cornell University. Please contribute! Contact PPN Co-Chairs Laura Tenny, ASLA, or David Cutter, ASLA, to tell your story.

MIT

MIT’s campus stretches approximately 1.5 miles along the banks of the Charles River basin in Cambridge, MA. Nearly 170 acres in size, and more than 65% impervious, the urban campus is home to about 2,300 trees. MIT’s trees are subject to typical urban stresses: street trees surrounded by pavement, trees framing high-use lawns that host special events (with associated tents, tables, chairs, and logistical support), and soils compacted from heavy foot traffic and pathway desire lines and spill-over.

MIT’s Manager of Grounds Services, Norman Magnuson, oversees MIT’s urban forest. He undertook the first MIT campus tree inventory in 2008. The scope of MIT’s first tree inventory assigned a unique identifier number to each tree, and recorded genus/species, native/non-native, general health, and diameter at breast height (DBH). Trees were tagged with RFID (radio frequency identification) tags. There were challenges with the system: RFID tags had no visible accession number so a tree could not be identified by sight, staff found the tag-reader technology difficult to use in the field, and because of the difficult user interface, it was not easy to add trees to the inventory. Updates happened only when trees were removed, such as for disease or construction projects. Given these challenges, the first inventory system ultimately was not used for tracking trends in the canopy or for an annual tree maintenance program. Aluminum-plate tree tags nailed to the trunk have been left on for nearly a decade, and in many cases the bark has occluded around the tag, resulting in a bark wounds.

Old and new methods of attaching tags. Occluded bark has begun to grow around the RFID card; it should be removed before it becomes further ingrown. / image: Laura Tenny

An updated tree inventory is planned for 2017, factoring in lessons-learned and advances in tree inventory systems. The new inventory will:

  • Provide a GIS-based inventory that will GPS-locate all trees and measure size to the nearest 1” DBH.
  • Identify genus and species (and cultivar when known).
  • Assess condition, maintenance needs, and provide a risk assessment of each tree.
  • Inventory stumps, identifying visible replacement needs.
  • Provide and mount to each tree a brass tag with a visible number.
  • Notate special resource areas (such as the elm and oak allees in Killian Court, where Commencement is held) and specimen trees such as memorial trees.
  • Provide a monetary value, for potential of assessing liquidated damages, demonstrating financial asset of the tree canopy.
  • Output summary reports that estimate ecological system services, such as carbon sequestration, stormwater management, and air quality benefits.
Elm trees lining Vassar Street are a typical example of the trees in MIT’s collection. / image: Laura Tenny

Future enhancements by MIT may include having an intern take photos of every tree, in leaf-on and leaf-off seasons, and then tagging individual tree photos to each tree ID in the system. To select a vendor, MIT is conducting a competitive bidding process. A few common themes have emerged:

  • ISA-certified arborists will complete the survey, including conditions/hazard assessment.
  • For tagging, some vendors tag each tree with a physical tag; others use a QR code only.
  • There is a one-time charge for inventorying the trees, then an annual cost of licensing the proprietary software.
  • Web-based dashboard tools interface to work on both desktop and mobile devices.
Allees of elms and oaks lining Killian Court, the location of MIT’s annual commencement, will be designated a “Special Resource” area for a tree care program. / image: Laura Tenny

Besides providing a tool for collection management, MIT’s updated tree inventory will be a planning tool, for topics from stormwater management to resiliency planning as climate change predictions forecast both more frequent and intense storms and longer periods of heat and drought. A comprehensive tree survey that quantifies ecosystems services can help make the case that the campus’s urban forest is an asset deserving stewardship. An important part of our natural “infrastructure” system, MIT’s tree canopy contributes to water and air quality, cools urban heat islands, and enhances our urban environment.

by Laura L. Tenny, RLA, ASLA, Senior Campus Planner, MIT Office of Campus Planning, and Campus Planning & Design PPN Co-Chair

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