18 When assessing the form of young trees, the excurrent form was used as a benchmark. Form was assessed using a five lev- el rating system (Table 2). In young trees, ideally the branch- es should be evenly spaced vertically and radially up the stem. Looking on the tree from above, it should look like a spoked wheel with branches being small in relation to the trunk. On larger trees (trunk caliper of ≥100 mm), at least some branch- es will be permanent and these should be well spaced and remain relatively small compared to the leader (Gilman 1997). Structural defects on which data were collected (Table 3) were co-dominant stems, included bark, decay, deadwood and cross- ing or rubbing branches all of which may reduce the structural Table1. Summary of the number of trees assessed. Species Corymbia citriodora Platanus × acerifolia Pyrus calleryana Quercus palustris Ulmus parvifolia Total Count 48 104 79 65 52 348 Table 2. Tree form definitions. Rating Definition Excellent A clear, strong, and straight leader firmly rooted in the ground. A good level of taper up the stem, and a wide-angled branching structure with even arrangement vertically and radially. Good Fair Poor A clear leader, possibly slightly crooked or weakened by laterals, even spaced branches, and no major faults in the canopy. A clear leader, with a possible lean or kink. Asymmetries in the canopy or branch arrangement and possible a slight lean. No clear leader, with possibly multiple leaders, leaning or a lost leader. Heavy canopy asymmetry. Very poor No leader or multiple leaders. A heavy lean possibly with very strong canopy asymmetry. Tree may have been vandalized. Candidate for replacement. Table 3. Structural defect definitions. Fault Definition Codominant stems Included bark Low branching Stems “Equal in size and relative importance, usually associated with either the trunks or stems or scaffold limbs….” (Harris et al. 1999) Recorded if it occurred anywhere in the main stem, either low or high on the stem. Where bark is turned inwards at branch junctions instead of being pushed out (Harris et al. 1999), resulting in the branch or stem being weakly attached and prone to fracturing (Shigo 1991; Smiley 2003). This may occur anywhere in the canopy from small branches to codominant stems and stem should be pruned back or the whole tree removed. Canopy lift required. Branches low on the stem of a tree that has established or branches encroaching on the road or pathway. The removal of low branches earlier rather than later reduces the wound on the trunk. If branches were encroaching on paths or roads, they were also canopy lifted. These were listed as a fault to be pruned. Epicormic shoots “Sprouts upon the trunk” (Shigo 1991). They are not well attached to the trunk or stem and can present a hazard by breaking when they get larger. Suckers Normally arise from roots at or below the soil surface. They are often shoots from rootstock to which the tree was grafted. Suckers can be vigorous and are not the desired cultivar. Broken branches Branch may not completely break off and continue to grow with a weak point becoming a danger. Broken branches were pruned. Broken stems Deadwood Main stem is broken. Most of these trees needed replacement due to the structural defect that existed. Deadwood in the canopy requiring removal. Usually coincides with a low health rating. Rubbing or crossing Branches rubbing against each other wound, which not only weakens the branch but provides an open wound for entry of patho- gens. Removal eliminates the weak point; the tree can heal over quickly and the integrity of the tree is not compromised. Rubbing branches were pruned. ©2013 International Society of Arboriculture Ryder and Moore: Economic Benefits of Formative Pruning rating of the tree (Matheny and Clark 1994; Harris et al. 1999). Most of these faults could be corrected with pruning. Details of the pruning cuts required with secateurs, handsaw, or pole prun- er to remedy the structural defects in the canopies of the trees were recorded. Each pruning activity was timed and the costs associated with formative pruning calculated. A tree with good structure is highly unlikely to suffer significant failure while a tree with very poor structure has a high potential for failure. For each specimen, the trunk caliper (at 100–150 mm above ground level), the location of the specimen, any com- ments specific to the tree, and the date of inspection were recorded. Factors such as height and trunk caliper were measured quantitatively, but tree structure and form were assessed visu- ally using predetermined definitions employing ranking scales. Number of Cuts and Time Taken for Pruning Trees were inspected and structural defects were identified and recorded. Due to variations in the sizes of stems and branches, prun- ing was undertaken with secateurs (pruning shears), a handsaw, or with a pole pruner. An estimate of the number of pruning cuts required using the appropriate tool was made. Most of the struc- tural defects observed could be corrected with formative pruning. Estimates of Time Required to Prune a Tree In order to assign a time to all works and achieve a total time for each tree, pruning trials were performed. For pruning with seca- teurs, ten repetitions of pruning a branch were conducted. Branch sizes ranged from 9 mm to 16 mm. A total of twenty-six repeti- tions were completed for pruning a single branch with a handsaw. Branches with a diameter of less than 40 mm were pruned in one cut. Above 40 mm, the branch was pruned using the undercut meth- od (Harris et al. 1999). Branch size ranged from 19 mm to 90 mm. Twenty-five pruning repetitions were performed with the pole pruner. As size increased, the implement attached to the
January 2013
| Title Name |
Pages |
Delete |
Url |
| Empty |
Ai generated response may be inaccurate.
Search Text Block
Page #page_num
#doc_title
Hi $receivername|$receiveremail,
$sendername|$senderemail wrote these comments for you:
$message
$sendername|$senderemail would like for you to view the following digital edition.
Please click on the page below to be directed to the digital edition:
$thumbnail$pagenum
$link$pagenum
Your form submission was a success.
Downloading PDF
Generating your PDF, please wait...
This process might take longer please wait
