Arboriculture & Urban Forestry 35(3): May 2009 plants for urban greening purposes. However, the Amiata source, the slowest growing source, had the second highest root system efficiency, 0.00060 g water g-1 fine root dry weight day-1 and the conservative growth habit of the Amiata and Cerreta sources are of interest to urban foresters. The findings of this study show the great variation between and within species in economically and physiologically important traits to the nursery producers and urban foresters. More studies are needed to find other po- tentially better adapted sources for nursery production and the urban forest environment in a rapidly changing world climate. There was significant variation in growth and water use char- acteristics among the seedlings from the six seed sources (two seed source of each of three species) tested. Average seedling height differed by 229% among the seed sources. The Q. robur sources, and to a lessor degree the Q. cerris Sellano and the Q. pubescens Bazzano sources, had a resource allocation pattern of a species capable of rapid growth: a greater investment in above- ground biomass at the expense of belowground biomass. In part, because of greater seedling size, Q. robur Cascine seedlings used the most water seedling-1 day-1 , but had the lowest water ratio. Q. pubescens seedlings had the highest water use cm-2 cm-2 use cm-2 leaf area and highest leaf area-to-fine root dry weight leaf area and seedlings of the Q. pubescens Cerreta source, which was the shortest source, had the highest height-adjusted water use (g water day-1 seedling height). There were low correlations between seedling height and height-adjusted water use, which would allow for the selection of any plant height and height-ad- justed water use combination. Thus, seedlings with rapid growth and a conservative water use habit (fast growing seedling with low height-adjusted water use) could be selected. There is great variation between and within these three oak species in economi- cally and ecologically important traits from which to select and develop individuals or populations better adapted to stressful urban forest sites and to a changing global climate. Additional studies, preferably conducted with clonal material, are needed to determine if the seedling growth and water use characteris- tics described here are also expressed in larger sized plants. These species are not commonly available in North American nurseries. However, they may be candidates for North Ameri- can urban forests. These Apennine seed sources are found on limestone-derived shallow soils (www.soilmaps.it/download/csi- brochure se.a4.pdf). Thus, they have evolved in soil conditions not unlike those typical of the urban forests. The seed sources were collected from European Plant Hardiness Zones 8 to 9 [-12 to -1°C (10 to 30°F), www.uk.gardenweb.com/forums/zones/hx- eleg.gif]. However, the species are found in colder climates [Zone 6; (-23 to -18°C or -10 to 0°F); forest.jrc.it/forest_and_climate/ forest_trends/spdistribution]. There are specimens of Quercus cerris, Q. pubescens, and Q. robur at Dawes Arboretum, USDA Plant Hardiness Zone 5b/6a, so the species’ potential adaptive range is great. Further research is needed to determine the adap- tive potential of these species to urban forests of North America. LITERATURE CITED Abrams, M.D. 1990. Adaption and responses to drought in Quercus spe- cies of North America. Tree Physiology 7:227–238. Bruschi, P.G.G. Vendramin, F. Bussotti, and P. Grossoni. 2000. Morpho- logical and molecular differentiation between Q. petraea (Matt.) Lie- bl. and Quercus pubescens Willd. (Fagaceae) in Northern and Central Italy. Annals of Botany 85:325–333. 119 Curtu, A.L., R. Finkeldey, and O. Gailing. 2004. Comparative sequen- cing of a microsatellite locus reveals size homoplasy within and between European oak species (Quercus spp.). Plant Molecular Bio- logy 22:339–346. D’Alessandro, A. Saracino, and M. Borghetti. 2006. Thinning affects water use efficiency of hardwood saplings naturally recruited in a Pinus radiata D. Don plantation. Forest Ecology and Management 222:116–122. Damesin, C., and S. Rambal. 1995. Field study of leaf photosynthetic per- formance by a Mediterranean deciduous oak tree (Quercus pubescens) during a severe summer drought. New Phytologist 131:159–167. Damesin, C., S. Rambal, and R. Joffre. 1997. Between-tree variations in leaf δ13C of Quercus pubescens and Quercus ilex among Mediterra- nean habitats with different water availability. Oecologia 111:26–35. Damesin, C., S. Rambal, and R. Joffre. 1998. Seasonal and annual chan- ges in leaf δ13C in two co-occuring Mediterranean oaks: relations to leaf growth and drought progression. Functional Ecology 12:778– 785. Dumolin, S, A. Kremer, and R.J. Petit. 1999. Are chloroplast and mi- tochondrial DNA variation species independent in oaks? Evolution 53(5):1406–1413. Dupouey, L.L., and V. Badeau. 1993. Morphological variability of oaks [Quercus robur L, Quercus petraea (Matt) Liebl, Quercus pubescens Willd] in northeastern France: preliminary results. Annals of Forest Science 50, Suppl. 1. 35s-40s. Epron, D., and E. Dreyer. 1993. Long-term effects of drought on photo- synthesis of adult oak trees [Quercus petraea (Matt.) Liebl. and Q. robur L.] in a natural stand. New Phytologist 125:381–389. Fineschi, S., D. Taurchini, P. Grossoni, R.J. Petit, and G.G. Vendramin. 2002. Chloroplast DNA variation of white oaks in Italy. Forest Eco- logy and Management 156:103–114. Fini A., F. Ferrini. 2007. Influenza dell’ambiente urbano sulla fisiologia e la sulla crescita degli alberi. Italus Hortus 14(1):9–24. Fotelli, M., K. Radoglou, and H. Constantinidou. 2005. Water stress re- sponses of seedlings of four Mediterranean oak species. Tree Physio- logy 20:1065–1075. Galle, A., P. Haldimann, and U. Feller. 2007. Photosynthetic performan- ce and water relations in young pubescent oak (Quercus pubescens) trees during drought stress and recovery. New Phytologist 174:799– 810. Gieger, T., and F. Thomas. 2005. Differential response of two Central- European oak species to single and combined stress factors. Trees 19:607–618. Johnson, P.J., S.R. Shifley, and R. Rogers. 2002. Oak-dominated ecosy- stems. In: The Ecology and Silviculture of Oaks. CABI Publishing, N.Y. pp. 8–53. Kleinschmit, J. 1993. Intraspecific variation of growth and adaptative traits in European oak species. Annals of Forest Science 50, Suppl. 1. 166s–185s. Kremer, A., J. Kleinschmit, J. Cottrell, E.P. Cundall, J.D. Deans, A. Du- cousso, A.O. Konig, A.J. Lowe, R.C. Munro, R.J. Petit, and B.R. Stephan. 2002. Is there a correlation between chloroplastic and nu- clear divergence, or what are the roles of history and selection on genetic diversity in European oaks. Forest Ecology and Management 156:75–87. Krussman, G. 1986. Manual of Cultivated Broad-Leaved Trees & Shrubs. Bol. II, Prov-Z. Epp Translator. Timber Press, Portland, OR. Lo Gullo, M.A., S. Salleo, R. Rosso & Trifilo. 2003. Drought resistance of 2-year-old saplings of Mediterranean forest trees in the field: rela- tions between water relations, hydraulics and productivity. Plant and Soil 250:259–272. ©2009 International Society of Arboriculture
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