Arboriculture & Urban Forestry 41(6): November 2015 ing pests or diseases (e.g., Dutch elm disease: Himelick and Ceplecha 1976; Gregory and Allison 1979; Sherald and Gregory 1980; Baker and French 1985; see section "Pest and disease management"). Pruning costs are related to the type (and goals) of pruning performed (Ryder and Moore 2013). Municipal pruning costs Tree pruning costs are typically the most expen- sive maintenance item in municipal tree programs (Kielbaso et al. 1982; Kielbaso 1990; Tschantz and Sacamano 1994). Surveys in 1980 and 1986 reported that pruning accounted for 28% and 30%, respec- tively, of the municipal tree care budgets of U.S. cities (Kielbaso et al. 1982; Kielbaso 1990). Tschantz and Sacamano (1994) reported that tree pruning accounted for an average of 36.9% of tree care op- erations costs and mean pruning expenses were $130.04 per tree ($82.73 in 1994$). In a benefit- cost analysis for 10 street tree species in Modesto, California, U.S. McPherson (2003) reported that pruning was the greatest category of mainte- nance costs for all species, ranging from $91 ($63 in 1997$) per tree pruned for London planetree (Platanus acerifolia) to $328 ($226 in 1997$) per tree for Modesto ash (Fraxinus velutina ‘Modesto’). Privatizing tree care operation is oſten suggested as a method to reduce costs through potential effi- ciencies (e.g., shared equipment and labor costs across multiple jurisdictions) that the private mar- ket place may bring into the public sector (Diller 1975; Tate 1986; Tate 1987; Tate 1993). The data to support this was not found in peer-reviewed papers. New York City, New York, U.S., found contract- ing to improve flexibility and efficiency of tree care operations (Lough 1991). Similarly in Los Angeles, California, U.S., contracting tree-trimming services in combination with in-house staff was found to facilitate shiſting from a 16.5- to 6-year tree pruning cycle (Kennedy 1990). As reported in a local news- paper at the time, the City of Saint Paul, Minnesota, U.S., put the tree pruning operations out for bid and found the city workforce submitting the low- est bid of $35.64 per tree ($25.49 in 1999$) in com- parison to private firm bids ranging from $53–$144 per tree ($38–$103 in 1999$) (Duchschere 1999). A key to successful incorporation of private contrac- tors is developing definitive specifications that are inspected for compliance and enforced by city staff; 301 Henning (1990) and Klonowski (1991) provided mechanisms to evaluate contractor performance. Worker efficiency studies Even though tree pruning typically receives the greatest budget allocation of all municipal tree maintenance activities, it is still oſten underfunded in comparison to needs (Sievert 1988). For this rea- son, efficient allocation of resources for pruning is important. Tracking worker activities, productivity, and performance over time (per O’Brien and Jo- ehlin 1992) could help develop models of species- and size-specific required pruning time and esti- mate pruning time for future work while allocating maintenance resources appropriately (O’Brien et al. 1992). The size of the tree was found to be positively correlated to the time required to prune, for dispos- al, and the amount of woody debris collected during pruning operations (O’Brien et al. 1992; Churack et al. 1994; Zillmer et al. 2000). Thus, maintenance needs and costs of trees increase as the size of the tree increases (Miller et al. 2015; Nowak 1990). From an early work in the 1960s, Wagner (1970) reported that a three-person crew was most effi- cient, requiring 54 work-minutes per trim in com- parison to 59, 100, and 141 minutes for four-, five-, and six-person crews performing utility line prun- ing. In comparison, Overbeek (1979) reported that the City of Grand Rapids, Michigan, U.S., found a four-person crew to be most efficient. The challenge is to maximize worker productivity by developing standards for different operations and collecting data that can be used to make management deci- sions. Pierce (1980) reported that crews in Omaha, Nebraska, U.S., spent 36% of work time on pruning activities (although no information is provided on the size of the urban forest maintained by tree crews). Churack et al. (1994) authored the first study to describe through mathematical formulas the time requirements for pruning tree species in Milwau- kee, Wisconsin, U.S. They found a strong positive relationship between pruning time required and tree diameter for four common species: green ash (Fraxinus pennsylvanica), honeylocust (Gleditsia tricanthos), littleleaf linden (Tilia cordata), and Nor- way maple (Acer platanoides) (Churack et al. 1994). Waste wood stack time and waste wood yield were also quantified, as were trends similar to that as discovered with pruning time were discovered for ©2015 International Society of Arboriculture
November 2015
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