Arboriculture & Urban Forestry 40(5): September 2014 Melinda Bartlett, Environmental Affairs Officer, MTLA, Los Angeles, CA; August 12, 2011) and the LACC (pers. comm., Meghan Shearer, Program Manager, LACC, Los Angeles, CA; August 23, 2011). The data were separated into Coastal and Inland climate zones. Street trees were further divided into #15 container (nominally 56.8 L) and #24 box (61 cm × 61 cm × 61 cm). Species names were missing for 31% of all street trees planted. To avoid overestimating ecosystem services by assuming that these unidenti- fied trees were large-stature trees, they were matched to the medium-stature Jacaranda mimosifolia. Information on the numbers and species of park trees planted was provided by the Los Angeles RPD (pers. comm., Laura Baurenfeind, Principal Forester, and Leon Boroditsky, Tree Surgeon, RPD; September 5, 2011). Although RPD did not track tree planting numbers by species, they provided monthly tallies of planting numbers in each of five management zones (i.e., Griffith, Metro, Valley, West, Pacific) and a list of the most frequently planted species based on nursery invoices. The dis- tribution of trees among those species was assumed to follow the distribution for street and yard trees. All planted park and yard trees were #15 container. Monitoring Tree Survival and Growth Random samples of 98 street and 96 yard trees were surveyed during summer 2011 by LACC arborists. Street trees were planted between June 2006 and December 2007, while yard trees were planted between February and December 2006. Tree status was recorded as: present (same spe- cies as planted originally), present but different species, present but dead, not present but evi- dence it was planted, not present and no evidence tree was planted, and address not accessible. The DBH was measured for all live trees with a tape at 1.37 m above the ground to the closest 1.3 cm. Tree crown diameter was measured par- allel and perpendicular to the nearest street or building with a tape to the nearest 0.3 m. Tree height was recorded, but data were found to be unreliable and were not used in the analysis. Additional information was collected for mod- eling effects of sample trees on nearby building energy performance. Distance was measured if the tree was within 18 m of the nearest air-conditioned building and recorded by class: adjacent = 0–8 m, 289 near = 8.1–12 m, far = 12.1–18 m. Azimuth, or the direction the tree lies from the nearest building, was measured with a compass and recorded as one of eight intercardinal directions (i.e., north, north- east, east). Buildings within 18 m of the tree were assigned to one of three vintages, where a vintage consists of buildings of similar age, construction type, floor area, and energy efficiency character- istics. Vintages were: 1) pre-1950: low insulation levels, small conditioned floor area (CFA), large window area:CFA ratios; 2) 1950–1980: more ceil- ing insulation, lower window area:CFA ratios; and 3) post-1980: more wall insulation, more CFA, lower window area:CFA ratios. The type of air condition- ing equipment in the building nearest to the tree was recorded, where choices were: central air/heat pump, evaporative cooler, and wall/window unit. The extent to which buildings were retrofitted for energy efficiency could not be determined, which adds uncertainty to estimates of energy effects. Modeling Tree Growth Tree-growth models were developed from data col- lected on predominant street tree species growing in two reference cities—Santa Monica (Coastal) and Claremont (Inland)—and used as the basis for modeling tree growth (Peper et al. 2001). Using their tree inventories, a stratified random sample of 20 predominant species in Santa Monica and 22 species in Claremont were measured to establish relations among tree age, size, leaf area, and biomass. Biometric information (e.g., DBH, crown diameter, tree height, bole height) span- ning the life cycle was collected for 30 to 60 trees of each species. Leaf area was estimated from com- puter processing of tree crown images obtained by using a digital camera (Peper and McPherson 2003). Linear regression was used to fit predic- tive models with DBH as a function of age for each of the sampled species. Predictions of crown diameter, leaf area and height metrics were mod- eled as a function of DBH using best-fit models (McPherson and Peper 2012; Peper et al. 2014). Modeling Population Dynamics Annual mortality rates during the first five years of establishment were based on data obtained from the street and yard tree field survey and a park tree monitoring study by TreePeople (pers. ©2014 International Society of Arboriculture
September 2014
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