210 degree of variation in rooting potential of stem cuttings from F1 hybrids between P. occidentalis and Platanus orientalis L. (Pan- etsos et al. 1994). Similar wide variation in adventitious rooting of Taxodium shoot tip cuttings has been reported within prov- enances that would impact the potential to capture gains in broad sense heritability for other traits (King 2010; King et al. 2012). CONCLUSIONS Evidence presented herein confirms the potential to improve nar- row sense heritability improvements in the growth and aesthetic qualities of landscape trees by selection of proper provenances that grow larger, faster once established and possess a range of urban stress tolerance traits. Further gains may be obtained in broad sense heritability where vegetative propagation is possible, but it will be critical to elucidate clonal propagation/production methods to obtain these additional gains as the ability to adven- titiously root from shoot tissues does not appear to be associ- ated directly with improved growth traits. Work discussed herein demonstrates the potential for not only the selection of growth rates or aesthetic traits using provenance studies, but also inclu- sion of adaptive traits in cultivar selection that would result in a better adapted urban forest. In the United Kingdom, provenance recommendations have been issued by the Forestry Commission (Hubert and Cundall 2006) for some species. The development of similar recommendations on a regional basis for the urban forest would be useful in urban forest management in the United States. In addition to the work presented herein, preliminary screen- ing for tolerance in provenances of Taxodium to Cercosporidium sequoiae infection (McDonald et al. 2008), chronic and acute drought tolerance (Denny 2007), foliar and soil salinity exposure (Denny 2007), and alkalinity tolerance (Denny et al. 2008) have been completed. Studies to assess genotypic differences in re- sponse to flooding, resulting in differential soil oxygen levels, are underway in the hopes that a relationship with knee development can be identified permitting selection of genotypes with reduced knee development. Effects of branching angles of ortets on prop- agation of ramets and potential topophytic responses associated with provenance are also being investigated (King 2010). Methods of provenance evaluations discussed here are also being extended to the development of regionally adapted groundcovers and shrubs from native North American species for built environments. Acknowledgments. This project was funded in part by Texas AgriLife Research (formerly the Texas Agricultural Experiment Station) and grants from the Tree Research & Edu- cation Endowment Fund and the J. Frank Schmidt Family Charitable Trust. Mention of a trademark, proprietary product, or vendor does not constitute a guarantee or warranty of the product by the authors, Texas A&M University, Texas AgriLife Research, or other involved insti- tutions, and does not imply its approval to the exclusion of other products or vendors that also may be suitable. Arnold et al.: Potential for Selecting More Sustainable Urban Trees LITERATURE CITED Abrams, M.D. 1990. Adaptations and responses to drought in Quercus species of North America. Tree Physiology 7:227–238. Arnold, M.A. 2008. Landscape Plants for Texas and Environs, Third Edi- tion. Stipes Publishing, L.L.C., Champaign, Illinois, U.S. 1334 pp. Arnold, M.A. 2011. Providence provides provenances for proper plants. Nursery Management 27(9):46–49 Arnold, M.A., L.J. Shoemake, and M.W. Goyne. 1998. Seed selection and nursery production practices impact root regeneration and tree establishment. pp. 13–26. In: The Landscape Below Ground II. Proc. of a Second Intl. Workshop on Tree Root Development in Urban Soils. Intl. Soc. of Arboriculture, Champaign, Illinois, U.S. Bohm, W. 1979. Methods of Studying Root Systems. Springer-Verlag, New York, New York, U.S.. 188 pp. Bsoul, E., R. St. Hilaire, and D.M. VanLeeunwen. 2007. Bigtooth maples from selected provenances effectively endure deficit irrigation. Hort- Science 42:1167–1173. Denny, G.C. 2007. Evaluation of selected provenances of Taxodium dis- tichum for drought, alkalinity, and salinity tolerance. Ph.D. Disserta- tion, Texas A&M Univ., College Station, Texas, U.S. 142 pp. Denny, G.C., M.A. Arnold, and W.A. Mackay. 2008. Evaluation of al- kalinity tolerance of selected provenances of Taxodium Rich. Hort- Science 43:1987–1900. Flint, H.L. 1983. Landscape Plants for Eastern North America: Exclusive of Florida and the Immediate Gulf Coast. John Wiley and Sons, New York, New York, U.S. 677 pp. Garrett, H. 1996. Howard Garrett’s Plants for Texas. Univ Texas Press, Austin, Texas, U.S. 170 pp. Graves, W.R. 1996. Drought resistance in trees: an overview of mecha- nisms and new research with Iowa’s black maples. In: METRIA 9: Proc. of the Ninth Metropolitan Tree Improvement Alliance Conf. Accessed 04/02/2012. Guries, R.P., and E.B. Smalley. 1990. Selecting and testing elms: the Wisconsin elm breeding program. pp. 21–30. In: METRIA 7: Trees for the Ninties: Landscape Tree Selection, Testing, Evaluation, and Introduction, Proc. of the Seventh Conf. of the Metropolitan Tree Improvement Alliance. Accessed 04/02/2012. Houston, D. 1988. The importance of seed source to tree planting in the urban forest. pp. 67–79. In: METRIA 6: Selecting and Preparing Sites for Urban Trees. Proc. of the Fifth Conf. of the Metropolitan Tree Improvement Alliance. Accessed 04/02/2012. Hubert, J., and E. Cundall. 2006. Choosing provenance in broadleaved trees. Forestry Commission, Edinburgh, UK. 12 pp. King, A.R. 2010. Vegetative propagation and topophytic responses of se- lected baldcypress clones. M.S. Thesis, Texas A&M University, Col- lege Station, Texas, U.S. 96 pp. King, A.R., M.A. Arnold, D.F. Welsh, and W.T. Watson. 2011. Sub- strates, wounding, and growth regulator concentrations alter adven- titious rooting of baldcypress cuttings. HortScience 46:1387–1393. King, A.R., M.A. Arnold, D.F. Welsh, and W.T. Watson. 2012. Devel- opmental stage and growth regulator concentration differentially af- fect vegetative propagation of select clones of Taxodium Rich. Hort- Science 47:1–11. Kriebel, H.B., and C.-W. Wang. 1962. The interaction between prov- enance and degree of chilling in bud-break of sugar maple. Silvae Genetica 11:125–130. ©2012 International Society of Arboriculture
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