76 Bancks et al.: Volunteer- and Researcher-Collected Urban Tree Inventory Data experience to professional experience. Volun- teer demographics reflect all 14 communities and were not recorded separately for each com- munity. No analysis of volunteer performance based on demographic information was possible. Volunteer Training Experienced research and outreach staff from the University of Minnesota, Department of Forest Resources, trained volunteers in each community. All volunteers were provided with training manuals written by University of Min- nesota researchers specifically for the project, as well as custom-made field identification cards for the tree species most prevalent in the volunteers’ community. Volunteers in each community were trained to perform the same tasks: tree identification, measurement of trunk DBH in inches (to the nearest inch), and crown width (CRW) in feet (to the nearest foot), a quantitative condition rating of trees, proper use of inventory maps, completion of survey data sheets, and data entry in Microsoft® Ex- cel®. Volunteers were also provided with safety instructions for working in their communities. Volunteers were trained and instructed to identify trees to species when possible or to genus when they felt unable to properly iden- tify species. Trunk DBH was measured using a measuring tape at 1.37 meters above ground level. Crown width was determined by mea- suring two crown radii from the tree drip line to the trunk, separated by 90 degrees (U.S. Forest Service 2017). The two radii were summed to provide an average crown width. Condition-rating instruction focused on iden- tification and assessment of nine different char- acteristics when evaluating the condition of a tree—four were exclusive to canopy condition, and five were trunk condition assessments. Vol- unteers were provided photo identification cards and manuals with images and descriptions of tree defects to aid in identification and assess- ment of condition. The condition-rating crite- ria were assessed and given a numeric score in quarter-point increments. Crown condition cri- teria included: stag-heading, tip dieback, crown symmetry, and live crown ratio. Trunk condi- tion criteria included: cambium loss, presence of ©2018 International Society of Arboriculture exposed and/or decayed wood, sprouts or suck- ers, stem cracks, and included branch unions. Scores were grouped into categories to provide a quantitative ranking of the tree’s condition. Training in all communities began with classroom instruction focused on the basics of tree identification, concentrating on iden- tifying tree species by their leaves, bark, fruit, and buds. Classroom instruction also covered measurement of DBH and CRW, tree condi- tion rating, and how to properly record data and tree location on paper datasheets and maps. The classroom instruction was followed by field training and practice of the tasks cov- ered during classroom training. Volunteers were required to collect data in groups of two or three. Training methods varied between the two groups of communities, but were consistent within the two community groups. Completed inventory datasheets and maps were mailed to the University of Minnesota and the spread- sheets were emailed to researchers for analysis. Method One Volunteers from the first group of six commu- nities were trained over the spring and sum- mer of 2010. For these communities, training consisted of approximately a one:one ratio of classroom instruction to field instruction. The training manual was 62 pages long, covering all training topics, and included few images. Trunk DBH was measured using either a diameter tape and recorded as diameter or measured using a linear tape and recorded as circumference. Circumference measure- ments were converted to diameter when the data were entered into the spreadsheet. Volunteers were taught to convert their walk- ing pace to a linear measurement in feet during the field-training sessions. Researchers used a 15.25-meter tape, placed on the ground, and vol- unteers would walk along the tape to assess the average length of their individual pace. Crown width was then determined when a volunteer would walk from the trunk to the drip line, for the two crown radii, counting their paces as they walked. Volunteers recorded CRW as the sum of their pace converted to feet, based on their average pace determined during training.
March 2018
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