Arboriculture & Urban Forestry 38(5): September 2012 Arboriculture & Urban Forestry 2012. 38(5): 205–213 205 Provenance Experiments with Baldcypress, Live Oak, and Sycamore Illustrate the Potential for Selecting More Sustainable Urban Trees Michael A. Arnold, Donita L. Bryan, Raul I. Cabrera, Geoffrey C. Denny, Jason J. Griffin, Jeffery K. Iles, Andrew R. King, Gary W. Knox, Leonardo Lombardini, Garry V. McDonald, Cynthia B. McKen- ney, D. Thayne Montague, Genhua Niu, H. Brent Pemberton, Adam L. Purnell, Larry J. Shoemake, Daniel K. Struve, and W. Todd Watson Abstract. Ecotypic, clonal, and racial variation present in tree species across their native ranges represent a largely untapped opportunity to select superior seed sources or clonal materials to withstand a variety of unique environmental stresses imposed in built environments and managed land- scapes. This paper focuses on three important woody plant genera (Quercus L., Platanus L., and Taxodium Rich.) and researchers’ efforts to dis- cover superior genotypes with tolerances to environmental stresses, including alkaline soil conditions, moisture deficits, and temperature extremes. The study authors are also interested in exploiting geographic provenances and open-pollinated family selection to identify unique genotypes or populations having desirable ornamental attributes, rapid root regeneration potential, and/or desirable plant architecture. A discussion of current results, potential impacts on selection of urban forest trees for managed landscapes, and plans for future development and research are presented. Key Words. Built Environments; Managed Landscapes; Platanus occidentalis; Quercus fusiformis; Quercus virginiana; Seed Source; Taxodium distichum; Urban Trees. Attention to the provenance (genetic origin of seed sources) has long been popular in forestry breeding programs, culminat- ing in the extensive breeding efforts with southern pines (Pinus taeda L. and its relatives) and other conifers in the western Unit- ed States for a variety of silvicultural traits (Zobel and Talbert 1984). Subsequently, forestry programs using non-native species in tropical regions to augment or replace the cutting of native rainforests have received attention (Zobel et al. 1987). Many nursery professionals recognize the concept of seed source (lo- cation of seed collection), but few recognize the distinction of seed source from provenance (Arnold 2011). Provenance work for urban forest trees began as early as the 1960s (Kriebel and Wang 1962) and 1970s (Townsend 1977), but has seldom been attempted through large scale cooperative efforts as with spe- cies grown for commercial forestry (Struve 1982). Tree taxa in which provenance was researched for traits from a horticultural or aboricultural perspective, included some species of Acer L. (Kriebel and Wang 1962; Townsend 1977; Townsend 1983; Ware 1983; Pair 1994; Sibley et al. 1995; Graves 1996; Sibley et al. 1997; Zwack et al. 1998; St. Hillaire and Graves 2001; Bsoul et al. 2007), Quercus L. (Struve and McKeand 1994; Pounders et al. 2004; Struve et al. 2006; Purnell 2010), Picea pungens En- gelm. (Houston 1988), Alnus maritima (Marsh.) Muhl. ex Nutt. (Schrader and Graves 2000), Maackia amurensis Rupr. & Max- im. (Pai and Graves 1995), Ulmus L. (Guries and Smalley 1990), and Platanus occidentalis L. (Shoemake 1996; Shoemake and Arnold 1997; Shoemake et al. 2004). This initial work was of- ten conducted using taxa traditionally propagated from seed and thus was limited to gains in breeding/selection cycles associated with narrow sense heritability (variation associated with addi- tive genetic effects). With advances in vegetative propagation of some traditionally seedling grown taxa, for instance Taxodium (Zhou 2005; King 2010; King et al. 2011), it may also be fea- sible to capitalize on gains from broad sense heritability (gains associated with both additive and non-additive genetic variance). The purpose of this paper is to use results from selected stud- ies on three important North American native landscape tree genera (Taxodium, Quercus, and Platanus) to illustrate the po- tential to improve aesthetic traits and cultural characteristics of trees for built environments in urban and suburban landscapes. MATERIALS AND METHODS Three series of studies are highlighted as examples of the po- tential to use provenance selection and evaluations to enhance urban tree performance for a variety of growth, stress re- sponses, disease resistance, and ornamental characteristics. Taxodium distichum Studies Provenances of Taxodium distichum var. distichum (TD) and T. d. var. imbricarium from eastern Texas, U.S., to the Florida pan- handle (northwestern Florida) (Eastern Provenances, EP), transi- ©2012 International Society of Arboriculture
September 2012
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