Arboriculture & Urban Forestry 42(4): July 2016 symmetry, and reduced number or diameter of straight roots (Lindstrom and Rune 1999). Older trees planted from landscape nurseries have also been evaluated for stability. Trees trans- planted from a field nursery were more stable in the landscape than comparably sized trees planted from 170 L (Gilman and Masters 2010) or 270 L (Gilman 2013) containers and required signifi- cantly more bending stress to tilt trunks to various angles. In addition to the greater root ball mass per unit of trunk diameter from a field nursery, several factors could explain reduced stability of trees planted from containers compared to trans- planted, field-grown trees. In one of these studies, trees from 170 L containers had one-quarter the root CSA growing into landscape soil, one-third the root CSA/cm2 of trunk CSA, one-half the number of roots, two-thirds the number of roots/ cm2 trunk CSA, and smaller diameter roots mea- sured just outside the original root ball compared with field-grown trees (Gilman and Masters 2010). Other than Alvey et al. (2009), there are few published studies comparing stability a year or more following planting once stakes are removed. The purpose of this study was to evaluate trunk and root growth and lateral stability or anchorage one year aſter planting trees from both a field and container nursery for several above- and below- ground stabilization systems. An Acer rubrum cultivar (‘Florida Flame’) was chosen due to the pop- ularity of the taxon in North American landscapes. MATERIALS AND METHODS Trees Twenty Acer rubrum L. ‘Florida Flame’ trees in #30 (111 L) containers with soilless substrate were hand-selected from a container nursery to be similar in trunk diameter [57 mm trunk di- ameter, SD (standard deviation) 3.7] with straight trunks. Tree trunks were clear of branches in the lower 1.3 m. Twenty trees of comparable size (55 mm trunk diameter, SD 2.9), were hand-selected from a field nursery. All 40 trees were planted as liners from 3.7 L containers approximately 24 months earlier. Field-grown trees were dug five weeks prior to planting from an exceptionally well- drained Orlando, Florida, U.S., fine sand field soil at Marshall Tree Farm (Moriston, Florida, U.S.) 247 with a mechanical tree spade. Trees were placed back into the same hole in natural burlap in a flat- bottomed, 61 cm top diameter wire basket and cinched tight with string. Some new roots were growing through burlap when trees were picked up from the nursery a day prior to study initiation. Trees were planted 2.2 m apart in two rows spaced 3.6 m apart during the week of 23 March 2009 into flat-bottomed holes as deep as the root ball. Holes were square with 1.3 m long verti- cal sides. The top of the root ball and the root collar were positioned even with the landscape soil. Root ball edge was placed at the same dis- tance (30 cm) from the north edge of each hole. Site soil was added as backfill about half way up the root ball and was uniformly packed by the same person walking on the backfill with 20 steps. The remaining backfill soil was added to the top edge of the root ball and again lightly packed by walking, with 20 steps around the tree. Irrigation was applied (20 L) to the root ball surface once daily for the duration of the study, using three spray emitters with an identical vol- ume. Fertilizer (200 g, 16 N: 4 P2 applied in June 2009 to the soil surface of the plant- ing hole. Mulch was not added to the site; instead, three applications of glyphosate (Roundup®) were applied during the growing season to a 1.3 m wide strip centered on the trunk down each row. The plot was an open, flat field (Millhopper fine sand: loamy, siliceous, hyperthermic Grossarenic Paleudults) with 25 to 30 m tall trees several hun- dred m away at University of Florida in Gaines- ville Florida in USDA (1990) hardiness zone 8b. O5 : 8 K2 Stabilization System Installation Four stabilization systems were tested, includ- ing a staking system, a guying system, a root-ball anchoring system, and a non-stabilized control. The staking system (LP) used lodgepole pine wooden poles 2.5 m long with a 6 cm diameter driven vertically 0.9 m deep, 12 cm outside the edge of the root ball. Two stakes were used per tree, one on the east and one on the west side. Deep Root Arbortie® (Deep Root Partners L.P., San Fran- cisco, California, U.S.), 18 mm wide strapping was secured to the top of a stake, strung horizontally to the trunk 1.4 m from the ground, wrapped half way around trunk, and again secured to the same ©2016 International Society of Arboriculture O) was
July 2016
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