Arboriculture & Urban Forestry 41(1): January 2015 ing. Pruning cuts (reduction cuts, Gilman and Lilly 2008) up to about 15 mm diameter removed about half (50%, estimated) of the foliage on the pruned primary branches. Reduction cuts were made back to lateral branches that were about one-third of the diameter of the cut; the retained lateral branch was oriented away from the central leader, where pos- sible. Some double reduction cuts were made on pruned primary branches (Figure 1). Heading cuts were made in those few cases where the retained lateral branch had no branch at the position needed to remove an estimated 50% of foliage from the pri- mary (Figure 1). No branches were removed at the trunk. Two to six primary branches were pruned on each tree depending on crown structure. An esti- mated 15% or 20% of the foliage on the entire tree was removed with pruning. Trees were not pruned aſter planting except for the treatments described. 13 around the trunk. Chipped, whole-tree, line- clearance pruning debris was applied as mulch 1.8 m wide and 8 cm deep down each row centered on trunks. No mulch was applied to the root ball surface and mulch was not re-applied. Periodic glyphosate applications controlled weeds. Veg- etation between rows was periodically mowed. Trunk diameter 30 cm above soil (calculated from circumference measured with a diameter tape) and tree height to the topmost bud were measured at planting (May 2011) and at the completion of the study (August 2013), providing data from three growing seasons. Basal diameter of the five largest primary branches at the conclusion of the study was measured just beyond the union with a diam- eter tape (position B, Figure 1), as was the diam- eter of the trunk just above the union (position A, Figure 1). Distance between tree top at planting and the union with the trunk (distance C, Figure 1) was recorded for each of these five largest pri- mary branches. Bark inclusions in these five unions were visually evaluated as either 1) inclusion pres- ent (inclusion currently forming as indicated by a crack in the top of the union or no branch bark ridge currently forming) or 2) inclusion absent (a single branch bark ridge along 100% of the union). When in question, the union was pulled apart to confirm absence or presence of inclusions. Percent- age total branch cross-sectional area (CSA) growing from unions with inclusions was calculated as: CSA of branches with inclusions ÷ total CSA of the five largest branches (with or without inclusions) × 100. To evaluate anchorage in a strong storm, all 64 Figure 1. Pruning on primary branches >0.5 aspect ratio was accomplished in one of three ways: 1, 2, or 3. Sections A, B, and C were measured for each of the five primary branches with the largest diameter. Trees were irrigated daily in the growing season for the duration of the study with three emitters directing water onto the root ball. Fertilizer (400 g; 20 N, 0 P, 4.8 K) was applied June 2011, April 2012, July 2012, and April 2013 to an area of 1.2 m2 trunks were pulled during the week August 14–21, 2013 (one block each rain-free day) with an elec- tric winch attached to a cable about 1.2 m from the ground. Trees were pulled in the 10 degree north azimuth direction and the cable remained parallel to ground. A 3,629 kg capacity load cell (SSM-AF-8000; Interface Inc., Scottsdale, Arizona, U.S.) was placed in-line with the pulling cable. An inclinometer (model N4; Rieker Inc., Aston, Penn- sylvania, U.S.) was mounted to a fabricated steel plate (5.1 cm × 7.6 cm). The plate was secured to trunk base 15 cm from soil surface, which was just above the swollen flare at the base of the tree. Ten days prior to pulling 42 mm rainfall occurred; 71 mm fell the day aſter the first block was pulled and 14 mm fell the day aſter the third block was pulled. ©2015 International Society of Arboriculture
January 2015
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