218 guyline. Anchors were driven into the soil according to the manufacturer’s directions to a depth of 61 cm (24.4 in) at an angle inline with the guyline. Anchors were driven into the soil at a distance away from the bottom of the trunk equal to the distance from ground level to the tie-in point above the first major limb creating a 45° angle. Anchors were positioned 120° apart making them equidistant around the trunk. The wire–cable guylines were threaded through the provided 45.7 cm (18.3 in) long plastic tubing, where they wrapped around the trunk on top of the first major limb. Guylines were secured using the provided U-bolt cable clamps. Rebar and ArborTie Three ArborTie guylines Deep Root Partners L.P., San Fran- cisco, CA, www.deeproot.com; Figure 2F), made of polypropyl- ene, were wrapped around the trunk on top of the first major limb and secured by tying the end to the guyline with a no-slip knot. The 1.2 m (4 ft) long, 9.5 mm (0.38 in) diameter rebar was driven into the soil straight down. Rebar had a 90° bend, 5.1 cm (2 in) away from the top end. Distance from the tree to where the rebar was driven into the ground was equal to the distance from ground level to the tie-in point. The three pieces of rebar were equidistant from each other at 120° apart. Rebar were driven flush with ground level, and the guylines were wrapped around the 90° bend and secured with a no-slip knot. Terra Toggle™ Two 3.8 cm × 8.9 cm (1.5 in × 3.6 in [standard 2 × 4]) untreated pine lumber were placed on the root ball 5.1 cm (2 in) from the trunk on opposite sides. Lumber was cut the same length as the width of the root ball (53.3 cm [21.3 in]) and positioned parallel to each other. Terra Toggle™Earth Anchors (Accuplastics Inc., Brooksville, FL, www.accuplastics.com; Figure 2G) are plastic anchors driven 1.2 m (4 ft) into the ground with a water-jet driving tool provided by the manufacturer at an angle away from the tree. Earth Anchors were tied to low-stretch plastic strapping that secured the lumber tightly to the top of the ball. Lumber was positioned so the concave side contacted soil. Four total anchors attached to straps were used per tree. Two straps were connected with a metal buckle, and the slack between the two was removed with a strapping tool supplied by the manufacturer. Tree Staple™ Two 91.5 cm (36.6 in) long Tree Staples™ (model TS36; Tree Staple Inc., New Providence, NJ, www.treestaple.com; Figure 2H) were used to anchor the root ball. Tree Staples™ were positioned so the longer of the two prongs was driven into the soil as it slid against the side of the root ball. The shorter prong was driven into the top of the root ball. Tree Staples™ were positioned so the shorter prong was driven halfway between the trunk and the opposite side of the root ball. Tree Staples™were driven straight down until they were flush with the top of the root ball. T-Stakes Two 1.8 m (5.9 ft) long T-stakes were driven into the undis- turbed landscape soil 20.3 cm (8.1 in) outside of the backfilled soil (Figure 2I). T-stakes were positioned 180° apart with notches facing away from the tree to prevent strap slippage. T-stakes were driven in the ground 61 cm (24.4 in). Polyester seatbelt-type straps (1.8 m [5.9 ft] long, 5 cm [2 in] wide) were ©2008 International Society of Arboriculture Eckstein and Gilman: Landscape Tree Stabilization Systems tied to the T-stake, wrapped around the trunk, and secured to the strapping on the other side with a no-slip knot. Data Collection Two instruments were used to collect data during pulling tests to measure force (load cell) and angle (inclinometer). Data from the load cell and inclinometer were collected by a Data Acquisition System (National Instruments Corporation, Austin, TX) and re- corded on a laptop. The 909 kg (2000 lb) capacity load cell (SSM-AF-2000; Interface, Scottsdale, AZ) was placed inline of pulling. The inclinometer (±70° range; model N4; Rieker Inc., Aston, PA) was mounted to a fabricated steel plate (5.1 cm × 7.6 cm [2 in × 3 in]) with two 15.2 cm (6.1 in) long spikes. To measure tilt as the root ball rotated, spikes were pushed into the top of the root ball so the inclinometer was positioned 7.6 cm (3 in) above the root ball and parallel to the direction of pulling. Data were collected from both instruments at a rate of 2 Hz (2 times/sec). Data collected from the instruments was displayed in real-time during pulling tests on the laptop running LabView software (v: 7.0; National Instruments, Austin, TX). Experimental Design and Procedure A concrete pillar was poured as a stationary pulling point. Each experimental block in the field contained two each of the ten treatments for a total of 20 trees per block. Each system was pulled in two directions in each of the five blocks (Figure 1) for a total of 100 trees (ten systems × two directions × five blocks 100 trees). Each block, with the systems in random order, was planted in a 36.6 m (120.8 ft) diameter semicircle around the pillar. Bolted to the pillar was a mounting plate with a winch (K-2250 Work Winch; W.W. Grainger, Inc., Lake Forest, IL) and a two-sheave pulley (RP124; CMI Co., Franklin, WV) at- tached. The load cell was connected to the tree with a clevis and a U-bolt at one end and the two-sheave pulley at the other end with another clevis. No-stretch rope (AM Steel; Samson Rope Technologies, Inc., Ferndale, WA) 0.6 cm (0.24 in) in diameter was tied to the pulley on the tree (Rock Exotica™Omni-block; Thompson Manufacturing, Tulsa, OK) threaded through the sheaves of both pulleys and then through the winch. Trees were planted in 41 cm (16.4 in) deep holes dug before testing with a 61 cm (24.4 in) diameter auger for consistency in depth and width. This positioned the top of the root ball and the root flare even with the landscape soil. Trees were placed in the center of the hole, before adding backfill. Backfilled site soil was uniformly compacted by having the same person walk on the soil around the tree 20 times. All trees were pulled within 2 days of planting to minimize the effects of rooting-in. Once all 20 trees in the block were pulled, the next block was planted and pulled. The Alachua County soil survey was used to determine the amount of water to add (757 L [196.8 gal]) and the amount of time to wait (6 hr) to bring a 2.4 m × 2.4 m (7.9 ft × 7.9 ft) plot, 1.2 m (4 ft) deep, around each tree to field capacity for testing. The actual amount of water added (1135.5 L [295.2 gal]) was 1.5 times the amount needed (757 L [196.8 gal] × 1.5 1135.5 L [295.2 gal]), ensuring soil saturation consistency. Water was applied through polyvinyl chloride and low-profile sprinkler heads controlled by battery-operated timers. Each tree was pulled 6 to 6.5 hr after irrigation stopped. Added water simulated a large-volume rain event often associated with hurricanes and other storms and standardized soil moisture conditions among replicates.
July 2008
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