Arboriculture & Urban Forestry 39(5): September 2013 Arboriculture & Urban Forestry 2013. 39(5): 211–217 211 Effect of Transplanting Date and Harvest Method on Growth and Survival of Three Urban Tree Species in an Arid Climate Nematollah Etemadi, Rezvan Mohammadi Nezhad, Najmeh Zamani, and Mohammad Mahdi Majidi Abstract. The major challenges for transplanting trees in arid regions compared to temperate regions are higher mortality and slower rate of establish- ment. As such, date and method of transplanting can potentially improve survival and establishment as well as subsequent landscape performance of transplanted trees in arid climate. In the present study, three urban species commonly used in the Isfahan, Iran, landscape including eldarica pine (Pinus eldarica Medw.), white mulberry (Morus alba L.), and smoothleaf elm (Ulmus carpinifolia Gled.), were transplanted from January to June 2010, when mean air temperature was less than 10°C (early winter), between 10°C and 20°C (early spring), or more than 20°C (late spring). Half of the trees were bare root (BR) and half balled and burlapped (B&B). White mulberry and smoothleaf elm trees transplanted early in winter had the highest survival percentage over two years. The best survival for eldarica pine was observed in early spring transplanted trees. For all species, survival rate and trunk diameter increase of B&B trees were significantly greater than BR trees during the first year. Also, the first year’s shoot growth and shoot number of pine trees, and dieback on elm trees, were significantly affected by transplanting method. During the second year, tree growth and survival for all species were similar for B&B and BR trees. Annual shoot growth of eldarica pine and smoothleaf elm trees, but not white mulberry, equaled to non- transplanted trees by the end of third year after transplanting, suggesting a species-specific response for post-transplant establishment in arid climate. Key Words. Arid Climate; Balled and Burlapped; Bare Root; Cultural Practices; Eldarica Pine; Iran; Isfahan; Morus alba; Pinus eldarica; Relative Growth Rate; Shoot Growth; Smoothleaf Elm; Ulmus carpinifolia; White Mulberry. Rapid urbanization in most developing countries with dry cli- mate have resulted in the loss or cut off a multitude of mature trees present in the way of construction activities. Transplant- ing landscape-sized trees is the method of choice to counter this loss and to preserve trees that conflict with urban develop- ment projects. However, trees cannot easily reestablish in arid and semiarid areas due to adverse weather conditions, such as high temperature, high evapotranspiration, and water short- ages (Milton et al. 1994; Zhang et al. 2002). Mortality rate is up to 50% among newly transplanted urban trees in these areas and is still commonplace during early growing seasons follow- ing transplanting (Bainbridge et al. 2001; Hiron and Percival 2012), which increase the expenses associated with the main- tenance and replacement of failed trees. In addition to severe environmental conditions, this is due to the difficult growing conditions found in cities and towns, affecting post-transplant growth, vitality, and lifespan of urban trees (Bühler et al. 2007). Date of transplanting potentially affects tree growth and establishment as it dictates the specific physiological status of plant (e.g., dormancy, leaf drop, bud set, shoot expand- ing) as well as specific weather conditions (e.g., temperature and moisture, wind, light intensity and quality) that influence root regeneration capacity (Richardson-Calfee and Harris 2005). Autumn and spring are commonly considered as the best times for transplanting most trees and shrubs in climates characterized by wet springs and autumns due to the favorable soils and air temperature conditions and the absence of active shoot growth, all of which minimize the potential for desic- cation (Watson and Himelick 1997; Harris and Fanelli 1999; Richardson-Calfee and Harris 2005). Transplanting in dormant season, if the winter soil temperature remains high, provides opportunities for a tree to regenerate its root system prior to shoot growth in springtime (Buckstrup and Bassuk 2000). However, transplanting in the dormant season is not recom- mended in climates with severe winters (Harris and Fanelli 1999; Richardson-Calfee and Harris 2005). Conversely, spring transplanting before budbreak, usually avoids damages of cold weather. Transplanting when trees are approaching budbreak is associated with carbohydrate drain from roots, which may result in poor root regeneration (Dumbroff and Webb 1978). Tree species vary in their responses to season of trans- planting. While autumn transplanting could improve growth and survival of some species (Harris and Bassuk 1994; Harris et al. 1996; Buckstrup and Bassuk 2000; Harris et al. 2002), spring transplanting may be preferable (Watson et al. 1986; Harris and Bassuk 1994; Buckstrup and Bassuk 2000) or simi- lar (Watson and Himelick 1982; Kelly and Moser 1993; Har- ris et al. 2001) to autumn transplanting for other species. Method of transplant affects post-transplant establishment by influencing the volume of root loss during harvesting. Be- cause all of the soil is removed from a bare root tree, shipping and handling costs are lower, resulting in up to 33% to 50% cost reduction when compared to B&B trees (Buckstrup and Bassuk 2003; Sather et al. 2004; Trowbridge and Bassuk 2004). The ©2013 International Society of Arboriculture
September 2013
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