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Optimum Urban Tree Inventory Crew Size: Results from an i-Tree Eco Project at Auburn University by Nicholas A. Martin, Inventory Arborist, Bartlett Tree Research Laboratories; Dr. Arthur H. Chappelka and Dr. Edward F. Loewenstein of the School of Forestry & Wildlife Sciences, Auburn University; and Dr. Gary J. Keever, Department of Horticulture, Auburn University in Auburn, Alabama, as part of a Master's degree project. The 2009-10 inventory of the managed areas on campus encompassed 585 acres (237 hectares) and included 7,345 trees. Information collected from each tree included diam- eter at breast height (DBH), tree height, crown width, percent dieback, and a tree condition rating. The average DBH and height of all trees was 6.5 inches (16.4 centime- ters) and 28 feet (8.5 meters), respectively. A During the inventory, a one-, two-, or three-person crew collected and recorded data using a GPS unit that time- stamped the beginning and end of data collection each day. The average time spent per tree was determined for a subset of the total tree population. Only trees that had a DBH of ≤ 10 inches (25.4 centimeters) were used because our one-person crew only collected a very small number of trees with a DBH > 10 inches. A daily average was calculated by dividing the time spent inventorying per crew (a combination of the time spent at each tree and walking from tree to tree) by the total num- ber of trees inventoried per crew. An overall average time per tree was then derived by averaging the daily averages for each crew size. Our results on the evaluation of crew size are summarized in Table 1. Each crew was composed of personnel with different backgrounds, training, and experience in tree inventories and i-Tree Eco procedures. The only person that worked on each crew was the graduate student (Nick Martin); all other crew members were undergraduates in the Auburn University School of Forestry & Wildlife Sciences. The primary intent of our study was to conduct a 100 percent inventory using i-Tree Eco protocol; the results showed interesting trends in crew size and productivity. These data, although relative, can be very helpful for managers who want to conduct tree inventories. The number and size of trees to be inventoried will play a major part in deciding the crew size. These results suggest that a one-person crew is as efficient as a three- person crew; however, a two-person crew could be con- 16 complete tree inventory following i-Tree Eco proto- col was conducted on the Auburn University campus A team of two measures DBH during the Auburn University cam- pus tree inventory. Photo courtesy of Drs. Arthur H. Chappelka and Gary J. Keever Trees Crew Size 1 2 3 Inventoried 365 716 581 Average Time (minutes/tree) 2.1 1.8 2.2 Average Inventory (trees/hour) 28.3 33.9 27.5 Table 1. Crew sizes, number of trees inventoried by each crew size, and average number of trees collected per hour for each crew size for the subset of trees with a DBH of < _ 10 inches. sidered the most efficient due to inventorying the most trees/day. However, for smaller sites, a one-person crew could be sufficient, whereas for larger sites, a two-per- son crew may be optimal. More research is warranted in this area. A more detailed report of this research can be found in the September 2011 issue of Arboriculture & Urban Forestry. City Trees