288 the Phoenix metropolitan area by botanical family. Interestingly, 44.5% of these 401 trees were of the family Fabaceae. Of the trees in the family Fabaceae, 63.4% belonged to two desert-adapted genera, Parkinsonia and Prosopis. Table 2 shows the percentage distribution of crown condition ratings for trees at landscaped sites by four dominant urban land classification types. Overall, crown condition was rated very good for 42% and good for 42% of the trees with a mean crown condition rating of 3.2. When data were analyzed using MAG land-use classification types for each plot, residential sites had the greatest percentage of tree crowns Table 1. Numerical distribution of taxonomic families of land- scape trees found at sites within the Phoenix metropolitan area during spring 2010. Also shown is the numerical distri- bution of landscape tree genera within the family Fabaceae within the Phoenix metropolitan area during spring 2010. Taxonomic family Anacardiaceae Arecaceae Bignoniaceae Cupressaceae Fabaceae Fagaceae Juglandaceae Meliaceae Moraceae Myrtaceae Oleaceae Pinaceae Platanaceae Rosaceae Rutaceae Salicaeae Sterculiaceae Tamaricaeae Ulmaceae Verbenaceae Total Taxonomic genus Acacia Bauhinia Dalbergia Ebenopsis Leucaena Lysiloma Mariosousa Olneya Parkinsonia Prosopis Quercus Tipuana Vachellia Total Count 13 21 5 4 181 7 2 5 19 5 27 11 2 8 42 4 18 3 27 2 406 Count 15 2 9 3 5 12 1 7 76 39 1 1 10 181 Proportion 0.032 0.051 0.012 0.009 0.445 0.017 0.004 0.012 0.046 0.012 0.066 0.027 0.004 0.019 0.103 0.009 0.044 0.007 0.066 0.004 1.00000 Proportion 0.082 0.011 0.049 0.016 0.027 0.066 0.005 0.038 0.419 0.215 0.005 0.005 0.055 1.000 Table 2. Percentage distribution of crown condition ratings for trees at landscaped sites by land-use that were part of the 2010 CAP LTER Survey 200 project. Rating Poor z Commercialz Very Good 27% Good Fair 50% 15% 8% Institutional Transport Residential 19% 52% 19% 10% 26% 40% 27% 7% 50% 42% 6% 2% Survey sites were classified using Maricopa Association of Governments land-use classification types. Survey assessment from February to April 2010; N = 33, 27, 54, and 273 for commercial, institutional, transport, and residential, respectively. Martin and Stutz: Tree Health in Phoenix, Arizona, U.S. that were rated in very good condition and the least percentage of tree crowns rated that were rated in either fair or poor condi- tion. About one-half of trees found at commercial and institu- tional sites had crowns that were rated in good condition. Nearly one-third of the crowns of trees located at institutional sites and along transportation corridors were rated in either fair or poor condition, compared with only 8% of trees at residential sites. 2003–2007 Non-residential Tree Survey Over the five-year period, the number of trees at the 50 non- residential sites in the greater Phoenix area declined from 403 to 335, suggesting a 4.2% average annual rate of tree mortality. Table 3 shows the percentage distribution of crown condition ratings and types of problems of trees at the 50 non-residential sites plus the 15 non-residential sites selected from the Survey 200 study (65 total sites) during the winter of 2006–2007. The overall mean crown condition rating of trees sampled at these 65 sites was 2.6 (between fair and good). Although a majority of the tree crowns were rated as very good (17%) or good (44%), it was found that 15% of tree crowns were in poor condition. Biotic problems (diseases and pests) were visually detected for 41% of the trees, whereas abiotic problems were observed for about 23% of trees. Of the trees with crowns rated in poor condition, 90% had significant biotic and abiotic problems. Significant canopy dieback occurred in 17% of the trees and was associated with known disease problems in Fraxinus (ash decline caused by phytoplasmas) and Olea (Verticillium wilt), but was also associated with problems of unknown etiology in Pinus (pine blight) and Rhus trees. Other common disease and pest problems observed included slime flux, sooty canker, wood rot, aphids, and sapsucker bird damage. Sunscald of bark on the bole was the most common abiotic problem. Pruning problems including topping, bark tearing, presence of large stub, and flush cuts were observed for 70% of the trees. Physical/mechanical injury (greater than 5 cm in diameter) to roots, the trunk, or main scaffold branches was detected in close to half of the trees (ca. 46%). Wounding appeared to be mostly associated with damage caused by landscape maintenance equipment, automobile impacts, and vandalism. The mean crown condition and percentage of occurrence of biotic and abiotic problems of trees in the 11 most common botanical taxa are shown in Table 4. Overall, the crown condi- tion rating of Ulmus trees was highest and Quercus trees were Table 3. Percentage distribution of crown condition ratings and type of problem, biotic (disease and pest), abiotic, poor pruning, or wounding of landscape trees at 65 non-residential sites in the Phoenix metropolitan area. Non-residential survey assessment was during winter 2006–2007 (N = 707). Condition rating Very Good Good Fair Poor Type Problem Abiotic problems Biotic problems Poor pruning Wounding >5 cm diameter ©2013 International Society of Arboriculture % of all trees 17% 44% 24% 15% % of all trees 23.2% 41.0% 70.4% 45.8%
November 2013
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