142 Follett et al.: New Approach to Quantify Growth Response to Pruning man 2002); however, the current study suggests that the response rate from pruning generally healthy trees may not be affected by the gradient of hard- scape coverage in typical suburban environments where root exploration allows for access to root sub- strate over a much larger area then is exposed at the surface. Furthermore, the relatively broken hardsur- face of the areas studied may allow for a high amount of moisture infiltration. This may not be the case in a newer setting where the hardscape is still relatively impervious, or in a more dense urban environment where tree pits are much more confined spaces. The study collected data on three variables that could be correlated with available light levels at the pruning sites; trim type (V-trim vs side-trim), dis- tance between V-trim main stems at phase height (giving an indication of the opening in the crown), and V-trim azimuth (light penetration through opening due to orientation). Of all these variables, none were significant across all species, or at a species level. Researchers presume that the rela- tive high light environment, where overall most of the trees studied were in generally high light con- ditions, was cause for not picking up any signal. CONCLUSION The validity of using the TruPluse 360 as a device for measuring branch extension for regrowth following pruning has been proven. This method allows for the safe and efficient data collection at an effective rate. While there is great variation in branch growth following pruning, several key predictors have been identified. As predicted, species had an effect on growth rate, with A. saccharinum showing the high- est rate of growth following pruning. Inclination angle of regrowth had a small positive effect on two of the species (F. pennsylvanica and A. platanoides), and little effect on A. saccharinum. This has impli- cations for spatial planning around utility corridors where A. saccharinum exist, as more clearance may be required due to the propensity to develop strong horizontal growth. Pruning method had a strong effect on growth rate, and the data support indus- try initiatives to promote directional pruning in the utility corridor to reduce the rate of regrowth. While a few factors were identified as significantly affecting branch regrowth, the high proportion of re-growth not accounted for points for the need to investigate further other possible factors. Factors such as over- ©2016 International Society of Arboriculture all tree vigor, carbohydrate storage, the timing of the pruning, and hydraulic position within the crown are possibly promising factors for future studies. LITERATURE CITED Becker, P., F. Meinzer, and S. Wullschleger. 2000. Hydraulic limita- tion of tree height: A critique. Functional Ecology 14:4–11. Bolund, P., and S. Hunhammar. 1999. Ecosystem services in urban areas. Ecological Economics 29:293–301. Canham, C.D. 1988. Growth and canopy architecture of shade- tolerant trees: Response to canopy gaps. Ecology 69:786–795. Chapin, F.S., E.D. Schulze, and H. A. Mooney. 1990. The ecology and economics of storage in plants. Annual Review of Ecology and Systematics 21:423–447. Chen, R., E. Rosen, and P.H. Masson. 1999. Gravitropism in Higher Plants Plant Physiology 120:343–350. Close, R.E., P.V Nguyen, and J. J. Kielbaso. 1996. Urban vs. natural sugar maple growth: I. Stress symptoms and phenology in rela- tion to site characteristics. Journal of Arboriculture 22:144–150. Dahle, G., and H. Holt. 2006. Branch strength loss implications for silver maple (Acer saccharinum) converted from round-over to V-trim. Arboriculture & Urban Forestry 32:148–154. Dwyer, J.F., E.G. Mcpherson, H.W. Schroeder, and R.A. Rowntree. 1992. Assesing the benefits and costs of the urban forest. Journal of Arboriculture 18:227–234. Goodfellow, J.W., B. Blumreich, and G. Nowacki. 1987. Tree growth response to line-clearance pruning. Journal of Arboriculture 13:196–200. Grabosky, J., and N. Bassuk. 1995. A new urban tree soil to safely increase rooting volumes under sidewalks. Journal of Arbori- culture 4:187. Grabosky, J., and E. Gilman. 2002. Measurement and prediction of tree growth reduction from tree planting space design in estab- lished parking lots. Journal of Arboriculture 30:154–164. Gregg, J.W., C.G. Jones, and T.E. Dawson. 2003. Urbanization effects on tree growth in the vicinity of New York City. Nature 424:183–187. Heichel, G.H., and N.C. Turner. 1984. Branch growth and leaf num- bers of red maple (Acer rubrum L.) and red oak (Quercus rubra L.): Response to defoliation. Oecologia 62:1–6. Heilman, P. 1981. Root Penetration of Douglas-fir Seedlings into Compacted Soil. Forest Science 27:660–666. King, D.A. 2003. Allocation of above-ground growth is related to light in temperate deciduous saplings. Functional Ecology 17:482–488. Kitajima, K. 1994. Relative importance of photosynthetic traits and allocation patterns as correlates of seedling shade tolerance of 13 tropical trees. Oecologia 98:419–429. Kosola, K., D. Dickmann, E. Paul, and D. Parry. 2001. Repeated in- sect defoliation effects on growth, nitrogen acquisition, carbohy- drates, and root demography of poplars. Oecologia 129:65–74. Krizek, D.T., and S.P. Dubik. 1987. Influence of water stress and restricted root volume on growth and development of urban trees. Journal of Arboriculture 13:47–55. Krueger, L.M., C.J. Peterson, A. Royo, and W.P. Carson. 2009. Eval- uating relationships among tree growth rate, shade tolerance, and browse tolerance following disturbance in an eastern decid- uous forest. Canadian Journal of Forest Research 39:2460–2469.
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