152 Etemadi and Nezhad: Production Method and Humic Acid Application in Arid Climate generally lose fewer roots and suffer less from trans- plant shock compared to BR trees. Therefore, the beneficial impact of HA on drought tolerance and nutrient uptake of B&B and CG trees may be less profound than on BR trees. Ferrini et al. (2005) reported that B&B English oaks treated with leon- ardite were rarely better than control trees regarding shoot extension, leaf area, and chlorophyll content. In another study, the effect of four different types of humate biostimulants was evaluated on CG Turk- ish hazelnut (Corylus colurna L.). No treatment experiment showed improved growth compared to untreated trees. Similar results were obtained for some container-grown landscape trees (Laiche 1991). Tree Establishment Several criteria of establishment following trans- planting have been proposed, including the time required to reestablish the original crown:root- spread ratio, or the time needed to resume the pre- transplant trunk growth or current-season shoot growth (Watson et al. 1986; Starbuck et al. 2005; Ross 2008). In the present study, tree establishment was evaluated by comparing current-season shoot growth and visual indices of transplanted trees to growth of untransplanted trees. By the end of the second year aſter transplanting, current-season shoot growth of all transplanted trees were statis- tically equal to the growth of same-sized untrans- planted trees, although shoot growth of BR trees was still lower compared to other methods. Also, no significant differences were observed between canopy color and canopy desiccation rates of B&B and CG trees, while both indices were substan- tially lower for BR trees. Therefore, it seems that B&B- and CG-transplanted trees were almost established during the two years, whereas the BR trees required more time to be fully established. Overall, the results of this study suggest that transplanting method has a strong influence on survival, growth, and establishment of oriental thuja trees. BR trees were not able to successfully tolerate the hardening-off period and did not show proper growth and survival following transplant- ing. The hardened-off CG trees performed better than freshly dug FG trees in terms of growth and percentage of vitality by the end of the first year. However, this initial advantage disappeared gradu- ally thereaſter. The practical significance of this ©2017 International Society of Arboriculture result is that the B&B transplanting method of ori- ental thuja would be both reliable and less expen- sive than the CG method for large-scale planting projects. This would be important particularly in arid climates with restricted water resources, as the hardening-off process of trees (CG or FG) needs more time and subsequently a greater water supply. On the other hand, results of this study do not support utility of humic acid as an aid to post- transplant establishment of oriental thuja trees. Acknowledgments. The authors would like to thank the Parks and Landscape Organization of Isfahan Municipality for financial sup- port of this research. LITERATURE CITED Amoroso, G., P. Frangi, and R. Piatti. 2010. Effect of container design on plant growth and root deformation of little leaf linden and field elm. HortScience 45:1824–1829. Anella, L., T.C. Hennessey, and E.M. Lorenzi. 2008. Growth of balled-and-burlapped versus bare-root trees in Oklahoma, U.S. Arboriculture & Urban Forestry 34:200–203. Apostol, K.G., F. Douglass, D.F. Jacobs, and R.K. Dumroese. 2009. Root desiccation and drought stress responses of bare root Quercus rubra seedlings treated with a hydrophilic polymer root dip. Plant Soil 315:229–240. Baigorri, R., M. Fuentes, G. González-Gaitano, J.M. García-Mina, G. Almendros, and F.J. González-Vila. 2009. Complementary multi-analytical approach to study the distinctive structural fea- tures of the main humic fractions in solution: Gray humic acid, brown humic acid, and fulvic acid. Journal of Agricultural and Food Chemistry 57:3266–72. Blessing, S.C., and M.N. Dana. 1987. Post-transplant root system expansion in Juniperus chinensis L. as influenced by production system, mechanical root disruption, and soil type. Journal of Environmental Horticulture 5:155–158. Buckstrup, M. 2004. Secrets laid bare. American Nurseryman 200:28–30. Buckstrup, M.J., and N.L. Bassuk. 2000. Transplanting success of balled and burlapped versus bare-root trees in the urban land- scape. Arboriculture & Urban Forestry 26:298–308. Chen, Y., M. De Nobili, and T. Aviad. 2004. Stimulatory effects of humic substances on plant growth. pp. 103–129. In: F. Magdoff and R.R. Weil (Eds.). Soil organic matter in sustainable agricul- ture. CRC Press, New York, New York, U.S. Clewell, A.F., and R. Lea. 1990. Creation and restoration of forested wetland vegetation in the Southeastern United States. pp. 195– 232. In: J.A. Kusler, and M.A. Kentula (Eds). Wetland creation and restoration: The status of the science. Island Press, Wash- ington, D.C., U.S. Etemadi, N., R. Mohammadi Nezhad, N. Zamani, and M.M. Ma- jidi. 2013. Effect of transplanting date and harvest method on growth and survival of three urban tree species in an arid climate. Arboriculture & Urban Forestry 39:211–217 Farahat, M.M., A.A.M Mazhar, and M.H. Mahgou. 2012. Response of Khaya senegalensis seedlings to irrigation intervals and foliar application of humic acid. Journal of Horticultural Science and Ornamental Plants 4:292–298.
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