224 Chappelka et al.: Determination of Crew Size Efficiency Relative to Urban Tree Inventories and soſtware, such as i-Tree Eco, are being used widely in the United States and other countries (Nowak et al. 2001; Escobedo et al. 2006; Esc- obedo 2010; Huyler et al. 2010) and can provide the resource manager with valuable information regarding urban ecosystem structure, composi- tion, and services (Nowak and Crane 2002; Martin et al. 2012; Nowak and Greenfield 2012; Nowak et al. 2013). However, information is lacking regarding crew size efficiency of data collection. The overall objective was to determine the time of data collection (for dbh, height, crown dimensions) using protocols developed for i-Tree Eco protocol (i-Tree 2010a; i-Tree 2010b; i-Tree 2010c) on a per-tree basis and relate this to the efficiency of crew size. A university campus is an ideal location for such a study (Martin et al. 2011a). Specifically, a random number of trees were sampled by one-, two-, or three-person crews, with the time from arrival to the tree to the completion of the data sampling recorded, and then the results analyzed and compared. MATERIALS AND METHODS Study Site and Personnel The study location was the Auburn University campus (32°36’N, 85°30’W), Auburn, Alabama, U.S. The managed areas on the core campus com- prise approximately 237 ha. The data collection occurred August 3 through October 23, 2011. An initial sample size of 90 trees was randomly selected (random numbers table) at-large from a previously conducted 100% (7,345 trees) campus inventory (Martin et al. 2011a). However, aſter an initial tree inspection, only 70 trees were included in the final analysis, due in part to removal or unapproachable trees resulting from ongoing con- struction on campus since the previous inventory (Martin et al. 2011a) was completed. To maintain consistency and remove bias in the study design, crapemyrtle (Lagerstroemia spp.) that comprised a large proportion of the initial data collection (approx. 20%) were collected using a different pro- tocol than the i-Tree Eco (Martin et al. 2011a) and were excluded from the current study. Diameter measurements were taken at 0.3 m from ground line, because the majority of trees were not mea- sureable at breast height due to their inherent form. ©2015 International Society of Arboriculture Each crew was comprised of personnel with dif- fering backgrounds, training, and experience with tree inventories and i-Tree Eco procedures. The only individual who had worked on the previous inven- tory (Martin et al. 2011a) was a full-time research assistant who was very familiar with the i-Tree Eco protocol, and the other two crewmembers were undergraduate students in the university’s School of Forestry & Wildlife Sciences. Before going to the field all members were trained in i-Tree Eco proto- cols (i-Tree 2010a; i-Tree 2010b; i-Tree 2010c). To ensure familiarity with the sampling procedures, all three individuals collected data separately and together from approx. 200 trees not included in the analysis to gain experience using i-Tree Eco pro- cedures before commencing the efficiency study. Data Collection The crews were sent to separate locations (15 trees) each time in an effort to reduce any inher- ent bias. Each tree in the re-inventory was visited by all three crew sizes, therefore each tree was vis- ited a total of three different times with identical measurements made on each occasion. The crews did not know which trees they would visit, the crew size, or composition of the crew until the day of data collection (i.e., the choice of the crew size to measure a particular location was arbi- trary to reduce bias). The selection of members in the one- and two-person crews was random and not always uniform (same members in each crew, except the three-person crew). However, each mem- ber (one- and two-person crews) participated in approximately one-third of the sample collection. All data were obtained following i-Tree Eco tree inventory protocol (i-Tree 2010c; Martin et al. 2011a). During the inventory, the crew (one to three individuals) collected and recorded data using a GPS (global positioning system) unit that provided a timestamp for when collection began and ended at each tree. The GPS used for the navigation as well as the data collection on each tree was a Trimble GeoXM GeoExplorer® 2005 Series (Trimble Navigation Lim- ited, Sunnyvale, California, U.S.). The tree heights and canopy measurements were made with a MDL LazerAce® Hypsometer (GeoSolution, Duluth, Geor- gia, U.S.). Diameter at breast height (dbh, 1.37 m) and crown width were determined using a loggers tape. The start and stop times were recorded to the
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