Arboriculture & Urban Forestry 36(6): November 2010 seconds. Trees were blown south with a custom designed and built 2.09 MW (2800 bhp) hurricane simulator capable of repli- cating turbulent wind loads powered by four 522 kW (700 bhp) Detroit Diesel marine engines. Each engine is coupled to two tandem 135 cc closed loop hydraulic pumps (model HPV-135; Linde Hydraulics, Munich, Germany) that spin at 2300 rpm. Flow through pumps was controlled by a 10-bit digital value controller (model DVC 10-ZZZ; Linde Hydraulics) that relates a linear input signal to a pulse width modulation sent to a digital servo valve control actuating a 22 deg swash plate. Pressure is then delivered through 120 MPa burst pressure hoses (model FC 606-20; Aeroquip-Vickers, Inc., Cleveland, OH, U.S.) to closed loop hydraulic motors (model HMA210; Linde Hydraulics) producing approximately 201.3 kW (270 bhp). Direct drive hy- draulic motors in turn spin a 4 x 2 array of 1.37 m diameter vane axial fans (model 54D550-VJ-1760-445T-X; Aerovent Indus- trial Fans, Lookout Mountain, TN, U.S.). Each fan is equipped with nine adjustable pitch blades that deliver 75 m3 ·s-1 at free air delivery. Desired flow conditions are maintained through an adjustable open loop control system derived from the lin- ear relationship between fan revolutions per minute and wind speed that accounts for inertial effects of the vane axial fans. Six custom-designed, steel reinforced, neutral shape NACA airfoils were mounted at the trailing edge of the contraction unit directly down-wind of axial fans. Airfoils were computer con- trolled with a 100Hz HR Textron valve (model 27B; Flow Prod- ucts, Inc., Bellingham, WA, U.S.) and HR Textron dual feedback loop PID control card (model EC250GP) which instructs a 138 N-m hydraulic rotary actuator (model HS-006-2V; Micromatic, Berne, IN, U.S.) and a custom active control system built with National Instruments Labview 8.5 software (Austin, TX, U.S.). The entire fan array rested on a trailer, making it mobile. It was hauled by tanker truck that also served as an 18,930 L radiator. The result was an actively controlled hurricane simulation ca- pable of creating ~1 kPa velocity pressure. The control system modulated wind speed by varying fan RPM. The control sys- tem utilized multiple fast running PID-control assembled with National Instruments hardware (NI PXIe-6704 chassis and NI PXI-6704 analog output data acquisition card) and a custom active control system operated in the Labview environment. Root Measurements Trees were dug from soil using a 137 cm diameter tree spade following pulling; soil was washed from outer edge of root ball. The diameter of all roots > 3 mm diameter was measured 5 cm beyond the original (at planting) root ball edge in top 25 cm of soil profile. Only roots in top 25 cm soil were excavated since Marshall and Gilman (1998) found few differences between nursery production methods at greater depths. Root diameter on each root was measured by averaging largest diameter and di- ameter perpendicular to largest. Distance between root and soil surface was recorded as root depth. Azimuth north from trunk center to point of root diameter measurement was recorded for each root; roots were divided into those growing out into soil from 0–13 cm and 13–25 cm depths. Azimuth was then divid- ed into six equal parts including leeward (toward winch) and windward (away from winch) one-sixth (60 degree) sections, and leeward and windward one-half (180 degree) sections. 283 Statistical Analysis Trunk bending moment (pulling force × distance from pull- ing point to inclinometer), trunk bending stress, trunk angle from unloaded start position (tilt) in pulling tests, root diame- ter, root number, root CSA, resting angle, and tree subsidence were compared among four planting treatments using GLM one-way analysis of variance in SAS. Means were compared using Duncan’s multiple range test. Tilt values measured dur- ing wind tests were compared between field and 170 L container treatments with t-test. The presence of trunk cracks was com- pared using proc GENMOD command in SAS as a binomial and log10 calculate exponent b in the equation: moment = a (caliper)b ing the Contrast statement. Trunk caliper and overturning mo- ment were log10 transformed; planting treatments were compared us- transformed and regressed onto one another to , a = moment when caliper = 1. The GLM procedure was used to calculate least squares coefficients of linear and quadratic rela- tionships between bending moment and trunk caliper + root CSA. RESULTS Trees transplanted from the field produced more root CSA into landscape soil and root CSA (cm2 )/cm2 trunk CSA, greater root diameter, and greater mean diameter of the 10 largest roots than trees from either 57 L or 170 L containers (Table 1). There was no difference in root CSA for trees planted from 57 L compared to 170 L containers. Trees transplanted from the field also had greater number of roots growing into landscape soil than trees planted from either container size (Table 1; Figure 1; Fig- ure 2). Root number/cm2 than for trees planted from 170 L containers, but was similar to trees planted from 57 L containers. Root diameter/cm2 trunk CSA for field trees was greater trunk CSA was greater for trees planted from 57 L containers than trees planted from any other treatment except field-grown trees. Trees planted from 57 L containers settled deeper into landscape soil the first three growing seasons following plant- ing than trees from 170 L containers and trees transplanted from field (Table 1). Trees planted from 170 L containers also settled deeper than field-grown trees. In contrast to contain- er-grown trees, field-grown trees rose two millimeters out of the ground the first three growing seasons after transplanting. Trees planted three growing seasons previously from 170 L containers tilted significantly more (P < 0.01) than trees trans- planted from the field when subjected to a given wind speed up to 45 m·s-1 trees to about three degrees and 170 L container planted trees to about 10 degrees corresponded to approximately 45 m·s-1 (Table 2). Tilting the lower trunk on field transplanted wind. tilt = 1.77 trunk caliper (cm) – 14.07, R2 slope P < 0.001. a significant relationship existed according to Equation 1. [Equation 1] MB around base (kNm) to 10 degrees trunk = 0.86, intercept and Bending moment required to tilt the lower trunk 10 de- grees from the nonloaded start position was less for trees planted from 57 L containers than other treatments; the bending moment required to tilt trunk 10 degrees was great- er for trees transplanted from the field (Table 3). A least squares regression for all 28 trees in the study of bend- ing moment (MB in kNm) against trunk caliper (cm) showed ©2010 International Society of Arboriculture
November 2010
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