current CTLA method to Benefit/Cost Public Tree Management appraise tree value is through a market approach National High Estimate Public Trees as used in this study (Cullen 2005). Adjusting the 1956 I-Tree Estimate Milwaukee Elm Trees and 1979 values to 2014 Best Sanitation Practice gives $145.34 which is CTLA Method Milwaukee Elm Trees consistent with the current Best Sanitation Practice wholesale market price ($130 to $146) for two inch National Low Estimate Public Trees caliper trees comparable to American elm (Wolter 0 1 2 3 4 2015). Further, maintenance Benefit/Cost costs ($0.88 per diameter inch) and tree removal costs Figure 43: Benefit to Cost Ratios of Urban Trees from Various Sources and ($5.66 per diameter inch) Methods. derived from 1980 data were comparable to 2014 values for maintenance ($2.07 to $2.54 per diameter inch) and removal ($15.30 per diameter inch) using cost accounting data from City of Milwaukee Forestry Operations. Two tree valuation systems were used to evaluate management options. Both the compensatory value (CTLA) and the environmental services (i-Tree Eco) approaches gave the conclusion that active management was better than no management and in order from Best > Good > Fair > Actual Outcome > No Control. VanNatta et al. 2012 used this same approach to evaluate management approaches for EAB management. They found that both the compensatory (CTLA) and environmental services (i-Tree Streets) were consistent and active management was better than No Control. McPherson (2007) also used a multiple approach using a cost approach (CTLA compensatory value) and benefit approach (environmental services) finding that after 40 years green ash (Fraxinus pennsylvanica) gave $5,807 per tree using the cost approach and between $3,102 and $5,022 from the benefit-based approach. This study found after 40 years the CTLA approach ranged from $2,125 (Fair control) to $2,254 (no DED scenario) on average for all trees that survived or died during the simulation time period included in the calculation. The benefit-based approach yielded a $6,297 total value from 40 years between the sum of $1,466 in ecological values and $4,831 in structural value at year 40 for the 11.78 inch dbh elm tree that survived and became larger. Tree Structure Modeling Knowing the structure (e.g., tree species, size, condition, canopy dimensions) of an urban forest is necessary to estimate environmental and aesthetic functions. No tree inventory existed for 1956 except the number of ROW elms trees. To solve this technical challenge, more recent tree inventory information was backcasted to reflect the 1956 population. Backcasting tree growth by subtracting a known tree growth rate has been used in rural forests modeling (Pommerening and Muszta, 2015). In this study, the use of this approach is the first time we know of that it was done with an urban tree population. To account for missing information on the size, height, and canopy dimensions of elms, models relating tree diameter to canopy spread and tree height used data for American elm street trees from Milwaukee. Estimating tree height and canopy spread has been commonly used with urban trees with
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