Arboriculture & Urban Forestry 43(2): March 2017 the Italian, Swiss, and Peñalolén formulas, with an average of USD $574 for first one. In the bot- tom quartile, with the lowest values, were the CTLA, French, and Danish (USD $161) formulas. DISCUSSION The results show that in using average monetary values, the Danish Method delivered low values, with an average of USD $207, and a median USD $161. The Swiss Method, as reported by Conta- to-Carol et al. (2008), resulted in the fourth low- est average value (USD $548). The Burnley had the fourth highest average value (USD $2,688) in contrast to what was reported by Ponce-Donoso et al. (2012). However, findings were consistent with these same authors regarding the CTLA and French Methods (Contato-Carol et al. 2008; Ponce- Donoso et al. 2013). In regards to the two Chilean formulas analyzed (i.e., Peñalolén Method and COPIMA), the findings were similar to those re- ported by Ponce-Donoso et al. (2009; 2012; 2013). These authors found that intermediate values were obtained, and the COPIMA continued to per- form better with regards to the Chilean formulas. A wide dispersion in the average rankings were also found (Table 3; Figure 1), with differ- ences of more than fourfold between the lowest and highest value, as exemplified by the Danish and French Methods with regards to the STEM formula, due to the fact they present statistically significant differences from the rest of the formu- las in Groups A, B, and I. The French Method was followed by the CTLA, Swiss, and Peñalolén for- mulas, whereas mean values were displayed by the Italian Method and COPIMA, forming a group with no statistical differences in their medians. The Tedesco and Norma Granada formulas dis- played slightly higher intermediate values. Finally, those with higher average values were the Burn- ley, Helliwell, and STEM formulas; the first two forming a group with no statistical differences in their medians (Group H; Table 3). Overall, the results showed a wide variability in the stud- ied formulas, whose differences in the valuation were due to their structural characteristics, and just as important, appraiser variability (Grande- Ortiz et al. 2012; Ponce-Donoso et al. 2013). When comparing the results and overall for- mula performance of the current study to those 79 reported by Watson (2002), researchers dis- covered similar findings exhibiting high vari- ability. While the Helliwell Method displayed the highest values in Watson’s (2002) study, the current findings show values from the Danish Method were followed by Helliwell, Tedesco, and Burnley Methods; and further, they showed no statistical significant difference when ana- lyzed separately according to appraiser (P < 0.05; Table 4). The remaining formulas did show dif- ferences between appraisers, with the greatest in the Peñalolén, COPIMA, French, Italian, and Swiss methods (P > 0.8); a finding pointed out by Watson (2002) when comparing these same formulas. Conversely, the CTLA, Italian, French, Norma Granada, COPIMA, and Peñalolén meth- ods showed the least variability, indicating that differences between appraisers were minimal. Considering that all formulas were parametric, their application in these three cites delivered both low and high values (e.g., CTLA and STEM Meth- ods) that differed with other studies (Watson 2002; Contato-Carol et al. 2008). It is not clear, however, which factor or parameter, either multiplicative or additive, is most influential and has the great- est weight in the total appraised value. Future research could analyze the sensitivity of each indi- vidual parameter separately, so as to recognize the weight they have in formula performance. Further, research is also needed on other key variables that could be used in these appraisal formulas, such as demographic characteristics (e.g., average mon- etary income of the city’s population), as well feasibility and viability of applying the formula. Researchers were not able to identify with any degree of certainty which of the formulas was best at assessing each tree, as the analyzed for- mulas performed dissimilarly. However, when analyzing the range and median of the ranking as performance criteria, the Norma Granada, CTLA, and COPIMA formulas performed well, relative to the others (Figure 1), by achieving low average values, which are relevant for the context in which the study took place. This was also corroborated by the lower degree of dis- persion [i.e., a high probability (Table 4)] and a median showing a distribution of values indicat- ing a fair appraisal. The formulas that had the highest values were the Helliwell and Burnley; ©2017 International Society of Arboriculture
March 2017
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