210 Martin et al.: 100% Tree Inventory Using i-Tree Eco Protocol Table 2. Tree characteristic totals for the most common species on campus. Parenthetical range represents the individual range for each species. Tree species Lagerstroemia spp. Quercus phellos Pinus taeda Magnolia grandiflora Quercus lyrata Ulmus parvifolia Acer rubrum Quercus nuttallii Quercus nigra No. of trees 1,639 596 565 464 363 331 289 250 194 Avg. DBH (cm) 12.1 (2.8–60.2)z 12.6 (5.1–142.5) 48.6 (5.1–135.6) 15.7 (3.6–104.6) 23.0 (4.8–123.7) 9.6 (5.1–83.1) 17.8 (4.1–60.5) 16.4 (6.4–56.4) 47.6 (4.6–126.5) Avg. height (m) 5.0 (1.8–13.7) 6.5 (3.4–20.4) 21.0 (3.1–41.5) 6.0 (2.4–17.4) 7.9 (3.1–22.0) 5.3 (3.1–15.6) 7.6 (3.4–14.9) 7.5 (4.3–16.2) 16.6 (3.4–30.5) Avg. crown width (m) 5.1 (0.3–12.2) 4.3 (1.5–21) 9.9 (2.1–22.6) 5.1 (0.3–18.9) 6.8 (1.8–31.1) 4.1 (0.9–18.9) 6.1 (2.4–18.0) 5.9 (2.4–15.3) 12.7 (3.1–32.0) Table 3. Contingency table for all trees on the Auburn University campus. This table contains dieback ratings and the corre- sponding overall tree condition rating. Dieback Ez G F P C D/D Total E 9 0 0 0 0 0 9 G 4,113 319 13 0 0 0 4,445 Overall Condition F 1,387 480 130 17 2 0 2,016 P 292 147 115 19 13 47 633 z E = Excellent, G = Good, F = Fair, P = Poor, C = Critical, VP = Very Poor, D/D = Dying/Dead Figure 4. Tree condition by diameter class using a) overall condi- tion class and b) percent dieback for the entire population. In terms of species composition, all three study sites were similar in that they all contained loblolly pine (Pinus taeda), red maple (Acer rubrum), and water oak (Quercus nigra) among their top ten most common species (Escobedo et al. 2009b; Huyler et al. 2010). The university campus and the cities of Auburn and Gainesville were also similar in that the majority of the trees had a DBH ≤15 cm (Escobedo et al. 2009b; Huyler et al. 2010). Auburn University differed from Auburn and Gainesville in tree density (no/ha); where the campus had 31 trees/ha, Auburn had 985 trees/ha (Huyler et al. 2010), and Gainesville had 348 trees/ ©2011 International Society of Arboriculture ha (Escobedo et al. 2009b). The campus also differed from the other study sites in canopy cover: the campus at 16%, Auburn at 49% (Huyler et al. 2010), and Gainesville at 51% (Escobedo et al. 2009a). The major differences in tree cover were due to the current study only encompassing the managed areas of campus, whereas the other studies included vacant (unincorporated for- est lands and vacant lots), residential, and industrial lands where basal area and density are generally much higher. It is hoped that in the future, data collected from 100% inventories using the i- Tree Eco protocol can be used to improve plot efficiency by im- proving the precision of the sampling technique for collecting information on the urban forest ecosystem structure and function. The evaluation of dieback was important because the model assigns tree condition according to the dieback rating. As i-Tree Eco was designed to assess ecosystem services that are often re- lated to leaf functions, it focuses its condition rating on crown condition. Dieback is an important factor when evaluating tree condition (indicator of crown integrity), but cannot alone be the determining factor, considering it is only one determinate of tree health. Managers who want to really understand and man- age their urban forests, and especially tree condition, must ex- amine the entire tree. The overall condition rating developed for this project included dieback as a functional rating but also took into consideration the structural condition of the tree—the key difference between the two ratings. It was determined that us- ing dieback as a surrogate for tree condition is not a sufficient indicator of overall tree condition. However, the results are based on comparisons between dieback and the overall tree condition rating developed for this project to provide a simple and quick assessment of tree condition; and comparisons using other condi- tion ratings may yield different results (CTLA 2000; CITYgreen 2010; ISA 2010). The authors’ current approach combined both crown and structural characteristics into one rating; however, pro- viding individual ratings for crown and structure may provide a VP 71 43 68 22 4 5 213 D/D 1 1 2 11 10 4 29 Total 5,873 990 328 69 29 56 7,345
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