Arboriculture & Urban Forestry 42(4): July 2016 Landscape Establishment and Anchorage Trunk diameter at 15 cm from ground, and height, on all 60 trees were measured at the end of every growing season in September through 2013 and 2012, respectively. Xylem water poten- tial on all 60 transplanted trees was measured on sunny days at one (April), two (May), five (Au- gust), and seven (October) months after trans- planting into the landscape. Irrigation had been withheld from one (April) to 23 (October) days prior to each measurement, according to Table 5. Xylem potential 12:00 to 14:00 hours was mea- sured with a pressure bomb (Soil Moisture Inc., Santa Barbara, California, U.S.). Terminal por- tions of current-year twigs in full sun about half way up the south side of the crown were cut about 10 cm long. Pressure in the air-tight chamber was increased at a constant rate of 30 sec·MPa-1 and was recorded when cut stem surface became uniformly wet. In September 2010, all trees were fertilized with 300 g of 20 N-0 P2 in March and June 2011 and April 2012 with 400 g spread under the tree crown. No prun- ing was conducted on trees after transplanting. Trees were winched to test anchorage in March O5 -8 K2 2011 and April 2012 (12 and 25 months aſter trans- planting, respectively) from a point approximately 1 m from the ground until the trunk base tilted five degrees. The cable remained parallel to ground. A 3,629 kg capacity load cell (SSM-AF-8000; Inter- face Inc., Scottsdale, Arizona, U.S.) was placed in-line with the winching cable. An inclinom- eter (model N4; Rieker Inc., Aston, Pennsylvania, U.S.) was mounted to a fabricated steel plate (5.1 cm × 7.6 cm) and the plate was secured to the trunk base 15 cm from soil surface, which was just above the swollen flare at the trunk base. The cable was winched at 2 cm·sec-1 until the inclinom- eter tilted five degrees from the vertical start posi- tion; tree was held for 60 seconds while distance was measured from trunk to the deepest point of the soil depression on the leeward side (hinge point) before relaxing the cable. Final angle at the trunk base was recorded as rest angle sixty seconds aſter relaxing the cable. No rain occurred dur- ing the three days required to winch all 60 trees. Data from load cell and inclinometer were col- lected at 2 Hz by Data Acquisition System (National O, and 237 Instruments Corporation, Austin, Texas, U.S.). Data were displayed in real time during winching on a laptop running LabView soſtware (v: 7.0; National Instruments, Austin, Texas, U.S.). Trunk bend- ing stress was calculated according to Equation 1: [1] [1] where 𝜎𝜎弶ﭒ = 𝐹𝐹弶ﭒ ∙ 𝑑𝑑弶ﭒ ∙ 𝑅𝑅弶ﭒ 𝜋𝜋弶ﭒ 4 ∙ 𝑅𝑅弶ﭒ 4 σ = bending stress F = pulling force d = distance from pulling point to incli- nometer R = trunk radius (calculated as halving diameter measured with a diameter tape at the inclinometer position) Experimental Design and Statistical Analysis The 38 and 57 L container trees were randomly assigned to positions in the container nursery. Experimental design in the field was a three-way factorial in a randomized complete block design with 3 liner container sizes × 2 root ball slicing treatments at container shiſting or field nursery planting × 2 field root pruning seasons × 10 blocks = 120 trees. Sixty trees (five complete blocks) were harvested and measured at the end of the field production phase trees; the remaining five com- plete blocks were transplanted. Three-way Analysis of Variance was used for each group to test for significance with container size, root ball slicing, and field root pruning season as main effects, and blocks as a random effect. Results were reported as significant at P < 0.05 unless indicated. Main effect means were separated by Duncan Multiple Range test; interactions were separated by LSD. RESULTS Field Production Liner container size had no impact on tree height in the field nursery in 2008 (Figure 1); however, trees planted from the smallest containers grew more in height in the last year (2009) of field produc- tion (P < 0.02) resulting in taller trees than those ©2016 International Society of Arboriculture
July 2016
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