Arboriculture & Urban Forestry 38(5): September 2012 231 Tree Measurements Tree height was measured with a height stick and trunk diameter 15 cm from ground (caliper) was measured with a diameter tape at landscape planting and at the end of each subsequent growing season in September of 2008 and 2009. Immediately after trees were pulled from the ground, all roots ≥3 mm in diameter were measured at the point just beyond the periphery of the original 57 L container root ball. Each root ball was divided into eight 45 degree wedge-shaped sections (N, NE, E, SE, S, SW, W, NW) marked with spray paint on the root ball top and bottom. The root ball was washed of substrate and soil. Root measurements included diameter (measured with a micro-caliper), quadrant lo- cation, distance between root ball periphery and tip of root when following the largest root at forks (in those few instances where roots had broken from the pulling operation, measurement termi- nated at the break), whether root emerged from the top or bottom half of the original root ball, and whether the measured root grew from a root that circled in the root ball more than a 90 degree arc (in these cases, the measured root was classified as a circling root) or not (these were classified as straight roots). Root data measured just beyond the root ball periphery was used to calcu- late a number of other attributes (Table 1). Roots greater than 3 mm diameter within the root ball that circled at the position of the 10 L or 57 L container were counted and their diameter measured where they appeared to first encounter the container periphery. Statistical Analysis Figure 1. Shaving (top) or slicing (bottom) root balls immediately after planting. Shaving severed 3 to 6 cm of roots and substrate from the root ball periphery but left them in place as shown. tent was standardized across trees for each growing season by waiting until no rain was predicted for the two-day pulling event, although soil moisture for the GS 1 pull (total of 2.8 cm rainfall occurred in the two weeks prior) may have been different than in GS 2 pull (total of 8.1 cm rainfall occurred in two weeks prior). Load cell and inclinometer measurements during pulling tests were sampled at 2 Hz (twice each second) using a 16-bit data acquisition system (National Instruments Corporation, Austin, Texas, U.S.) and displayed and archived in real-time on a laptop running LabView software (v: 7.0; National Instru- ments, Austin, Texas, U.S.). Trunk bending stress at position of inclinometer was calculated as: (pulling force × distance from pulling point to inclinometer × trunk radius at inclinom- eter center) ÷ (0.25π × trunk radius4 ) after James and Kane (2008). Bending moment at position of inclinometer was cal- culated as force × distance from pulling point to inclinometer. Data were analyzed in a randomized complete block design with one tree from each nursery planting depth (4) × root pruning at landscape planting (3) combination in each of four blocks. Two- way analysis of variance in the GLM procedure within SAS (SAS Institute, Cary, North Carolina, U.S.) was used to evalu- ate impact of main effects and interactions on measured param- eters for each year independently. The two main effects were planting depth into containers and root pruning at landscape planting. Means of main effects were separated with Duncan’s multiple range test. Pearson’s correlation coefficient (SAS Insti- tute, Cary, North Carolina, U.S.) was used to make correlations between root attributes and bending moment or bending stress. Significant results were reported at P < 0.05 unless indicated. RESULTS AND DISCUSSION All 48 trees survived and grew following planting into the land- scape; no dieback or leaf drop (other than normal leaf drop for this tree in late winter) occurred on any tree. Further study should test root pruning followed by less intense irrigation, which would be typical in landscape plantings. No interactions were statisti- cally significant. Planting depth when shifting rooted cuttings into 10 L containers or when shifting 10 L into 57 L contain- ers had no impact on trunk caliper (3.1 cm, P = 0.52) or tree height (256 cm, P = 0.78) of finished trees in the nursery in 57 L containers (data not shown). Gilman and Harchick (2008) also found that planting depth had no effect on growth of Cathedral Oak when shifting from one container size to the next up to 170 L. Other taxa showed little or no impact (Gilman et al. 2010a) or slower growth (Brown and Tilt 1992; Bryan et al. 2010) when planted deeply in containers. Planting depth in nursery con- tainers had no impact on trunk caliper (7.9 cm, P = 0.83, data ©2012 International Society of Arboriculture
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