Arboriculture & Urban Forestry 39(1): January 2013 end was changed from secateurs to the saw attachment. For branches with a diameter above 25 mm, the saw had to be used in favor of the secateurs. Branch size ranged from 9 mm to 48mm with an average size of 17 mm. As the trees assessed for formative pruning were a maximum of 6.5 m tall, the use of the secateurs attachment was most common due to small diameter branches occurring high in the young tree canopy. Total Time and Cost Total time was determined by multiplying the number of pruning cuts by the time taken to perform the operation derived from the pruning trials. This was added to the inspection time and travel time to provide a total time required for work on each tree. As the distance between trees was not uniform, the time taken to walk between ten trees was measured and then divided by ten. The total time required per tree was the total of the time taken per prun- ing cut multiplied by the number of pruning cuts plus travel time between trees and the allocated inspection time of 30 seconds. To determine a cost for formative pruning per tree, the amount of time required for pruning each tree was estimated. This involved counting how many cuts were required on the tree and then multiplying the number of cuts by a time factor. The use of a saw or secateurs attachment on the pole pruner took similar time. To assign a time to pruning a single branch with secateurs, a prun- ing trial was conducted. It was determined that branches up to 15 mm in diameter could be pruned using secateurs without strain. Pruning involved walking up to the tree, pruning off the branch with Felco® No. 2 secateurs, and removing it from the canopy and placing it on the ground. A sample of ten branches was selected and pruned. Few, if any, branches below 10 mm in size needed pruning. Pruning with a handsaw encompassed a wide range of branch sizes. With 15 mm being the smallest, a branch of up to 100 mm could be pruned relatively easily. Due to large size differences, the research utilized two handsaws. The first was a small ARS® turbocut handsaw with a 180 mm blade. This saw is lightweight, easy to use, and is good for small cuts as it fits easily into most branch crotches. This saw cuts easily up to 90 mm but a branch size limit of 50 mm was imposed. The second, larger saw for branches of 50 mm and larger was a Wolf® garden handsaw designed for attachment to the Wolf multi-star® Vario 220-400 pole, which allows for use in pole pruning. The blade is approximately 350 mm long and good for larger pruning jobs. Branches up to 40 mm in diam- eter were pruned in one cut, but to avoid damage when prun- ing, the undercut method was used for branches over 40 mm. An undercut was made approximately one quarter of the way through the branch and a second cut was made within 25 mm of the first cut on top of the limb and sawn until the branch broke. The third cut was made by cutting through the branch along the plane defined using the branch bark ridge (Harris et al. 1999). Pruning requirements above approximately two meters (the height of the reach of an arborist) required the use of a pole pruner. The pole used was a Wolf multi-star Vario 220-400, which extends 2.2–4 m with handsaw and secateurs attach- ments. The handsaw used was the same as the large handsaw as previously described. The secateurs could cut a branch diameter of up to 40 mm but 30 mm was considered a more appropriate maximum. Larger branches over 30 mm were pruned with the handsaw. The largest trees surveyed in this trial were approximately five to six meters tall, meaning that seca- 19 teurs were used most frequently. Equipment was easily carried in a carpenter’s belt with the pole carried in hand. Due to differ- ences in distance between trees along streets, a replicated trial was conducted to gauge the time taken to walk between two trees. All pruning used Natural Target Pruning (NTP) methods (Shigo 1991). NTP removes branches taking into account the tree’s natural branch shedding biology. An NTP cut is made beyond the plane defined by the branch bark ridge. If collars were visible the NTP cut was made close to but not through the collar (Standards Australia 2007). Once the data were col- lected, means, confidence intervals, uncorrected t-tests, ANOVA and regression were used to establish significance. Microsoft Excel and Minitab statistical package were used for the analyses. Cost of Labor and Mature Street Tree Pruning In order to compare the cost of formative pruning with struc- tural pruning in mature trees, a group of 37 trees in a car park were pruned for the first time at an age of approximately 20 years. Pruning was undertaken to remove codominant stems, crossing, dead and rubbing branches, broken or split branches, and the removal of any branches below three meters from the ground. Assuming a known inflation rate of between 3% and 5%, a cost for structural pruning of the young trees assessed in this research could be estimated for comparison with the costs calculated for formative pruning. A further calculation was made costing two formative pruning cycles at three and six years for comparison with other management strategies. In order to cost formative pruning, the market price on arboricultural labor was used. Two Melbourne-based arboricultural firms were consulted for quotations (Table 4). The average price was AUD $68.25 per hour. Table 4. Average price for arboricultural labor. Currency is represented in Australian dollars. Business Company A Company B Average Price $65/hour per person $71.50/hour per person $68.25/hour per person RESULTS There were no canopy structural defects in 78 trees, represent- ing 22% of the sample. The remaining 78% displayed at least one fault, suggesting that there is a need for formative prun- ing in all tree management plans. Over the range of trees sam- pled, work with the pole pruner was required most (Table 5). The average number of cuts required by the pole pruner was more than the work for the secateurs and handsaw combined. The occurrence of codominant stems (68%) throughout the canopy or trunk of the tree was the greatest fault, followed by included bark (40%) (Table 5). When both occurred together, the fault was magnified by the included bark in codominant stems, which is a major weakness in tree structure (Harris et al. 1999). Low branching in 17% of the trees was a reflec- tion of a need for a canopy lift to accommodate either vehicu- lar or pedestrian access. Rubbing and broken branches (12% and 14%, respectively) were common; however, epicormic shoots, broken stems, and deadwood occurred at low levels. The low value of deadwood is a reflection that the street trees were young and in good health. There was wide variation be- ©2013 International Society of Arboriculture
January 2013
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