Variations in leaf morphology and stomatal characteristics have been extensively studied at both inter- and intraspecific levels although not explicitly in the context of paper birch (Betula papyrifera Marsh) populations. The birch populations might have developed the leaf variations that allowed them to adapt to a wide climatic gradient. Therefore, in this study we examined variations in the leaf morphological and stomatal characteristics of sixteen paper birch populations collected across Canada and grown in a common garden. We also examined the relationship between these leaf characteristics and the climate of the population’s origin. Significant genotypic differences were found in the leaf characteristics measured among the birch populations. Thus, we expected that the observed leaf variations may be partly explained as natural diversity in the birch due to differences in environment of origin. We noticed that along mean annual precipitation and aridity gradients, hair density on leaf adaxial surface had decreased whereas stomatal density increased significantly. Our results showed that the populations with larger leaf area and specific leaf area had higher hair density but low stomatal density. These leaf characteristics provided a structural basis in reducing water loss through leaves and increasing water use efficiency. A trade-off between stomatal area and density resulted in this study might be a strategy of the birch to balance stomatal conductance in decreased precipitation.
 Teklehaimanot, Z., Lanek, J. and Tomlinson, H.F. (1998) Provenance Variation in Morphology and Leaflet Anatomy of Parkia biglobosa and Its Relation to Drought Tolerance. Trees, 13, 96-102.
 Warren, C.R., Tausz, M. and Adams, M.A. (2005) Does Rainfall Explain Variation in Leaf Morphology and Physiology among Populations of Red Ironbark (Eucalyptus sideroxylon subsp. Tricarpa) Grown in a Common Garden? Tree Physiology, 25, 1369-1378.
 Ivancich, H.S., Lencinas, M.V., Pastur, G.J.M., Esteban1, R.M.S., Hernández, L. and Lindstrom, I. (2012) Foliar Anatomical and Morphological Variation in Nothofagus pumilio Seedlings under Controlled Irradiance and Soil Moisture Levels. Tree Physiology, 32, 554-564.
 Bloom, A.J., Chapin, F.S. and Mooney, H.A. (1985) Resource Limitation in Plants—An Economic Analogy. Annual Review of Ecology and Systematics, 16, 363-392.
 Mclellan, T. (2000) Geographic Variation and Plasticity of Leaf Shape and Size in Begonia dregei and B. homonyma (Begoniaceae). Botanical Journal of the Linnean Society, 132, 79-95.
 Abrams, M.D. (1990) Adaptations and Responses to Drought in Quercus Species of North America. Tree Physiology, 7, 227-238.
 Abrams, M.D. (1994) Genotypic and Phenotypic Variation as Stress Adaptations in Temperate Tree Species: A Review of Several Case Studies. Tree Physiology, 14, 833-842.
 Werger, M.J.A. and Ellenbroek, G.A. (1978) Leaf Size and Leaf Consistence of a Riverine Forest Formation along a Climatic Gradient. Oecologia, 34, 297-308.
 Gates, D. M. (1980) Biophysical Ecology. Springer Verlag, New York.
 Picotte, J.J., Rosenthal, D.M., Rhode, J.M. and Cruzan, M.B. (2007) Plastic Responses to Temporal Variation in Moisture Availability: Consequences for Water Use Efficiency and Plant Performance. Oecologia, 153, 821-832.
 Ehleringer, J., Mooney, H.A., Gulmon, S.L. and Rundel, P.W. (1981) Parallel Evolution of Leaf Pubescence in Encelia in Coastal Deserts of North and South America. Oecologia, 49, 38-41.
 Fonseca, C.R., Overton, J.M., Collins, B. and Westoby, M. (2000) Shifts in Trait-Combinations along Rainfall and Phosphorus Gradients. Journal of Ecology, 88, 964-977.
 Cunningham, S.A., Summerhayes, B. and Westoby, M. (1999) Evolutionary Divergences in Leaf Structure and Chemistry, Comparing Rainfall and Soil Nutrient Gradients. Ecological Monographs, 69, 569-588.
 Pittermann, J. (2010) The Evolution of Water Transport in Plants: An Integrated Approach. Geobiology, 8, 112-139.
 Raven, J.A. and Edwards, D. (2001) Roots: Evolutionary Origins and Biogeochemical Significance. Journal of Experimental Botany, 52, 381-401.
 Batos, B., Vilotic, D., Orlovic, S. and Miljkovic, D. (2010) Inter and Intra-Population Variation of Leaf Stomatal Traits of Quercus robur L. in Northern Serbia. Archives of Biological Sciences, 62, 1125-1136.
 Beerling, D.J., Chaloner, W.G., Huntley, B., Pearson, J.A. and Tooley, M.J. (1993) Stomatal Density Responds to the Glacial Cycle of Environmental Change. Proceedings of the Royal Society B: Biological Sciences, 251, 133-138.
 Hetherington, A.M. and Woodward, F.I. (2003) The Role of Stomata in Sensing and Driving Environmental Change. Nature, 424, 901-908.
 Holland, N. and Richardson, A.D. (2009) Stomatal Length Correlates with Elevation of Growth in Four Temperate Species. Journal of Sustain Forestry, 28, 63-73.
 Raven, J.A. (2002) Selection Pressures on Stomatal Evolution. New Phytologist, 153, 371-386.
 Fraser, L.H., Greenall, A., Carlyle, C., Turkington, R. and Friedman, C.R. (2009) Adaptive Phenotypic Plasticity of Pseudoroegneria spicata: Response of Stomatal Density, Leaf Area and Biomass to Changes in Water Supply and Increased Temperature. Annals of Botany, 103, 769-775.
 Belhadj, S., Derridj, A., Moriana, A., Gijon, M.D.C., Mevy, J.P. and Gauquelin, T. (2011) Comparative Analysis of Stomatal Characters in Eight Wild Atlas Pistachio Populations (Pistacia atlantica Desf.; Anacardiaceae). International Research Journal Plant Science, 2, 60-69.
 Aasamaa, K. and Sõber, A. (2011) Stomatal Sensitivities to Changes in Leaf Water Potential, Air Humidity, CO2 Concentration and Light Intensity, and the Effect of Abscisic Acid on the Sensitivities in Six Temperate Deciduous Tree Species. Environmental and Experimental Botany, 71, 72-78.
 Ashton, P.M.S. and Berlyn, G.P. (1994) A Comparison of Leaf Physiology and Anatomy of Quercus (Section Erythrobalanus-Fagaceae) Species in Different Light Environments. American Journal of Botany, 81, 589-597.
 Bacelare, E.A., Correia, C.M., Pereira, J.M.M., Gonçalves, B.C., Lopes, J.I. and Torres-Pereira, J.M.G. (2004) Sclerophylly and Leaf Anatomical Traits of Five field-Grown Olive Cultivars Growing under Drought Conditions. Tree Physiology, 24, 233-239.
 Bayramzadeh, V. (2011) Stomatal Characteristics of Fagus orientalis Lipsky in Geographically Separated Locations in the Caspian Forests of Northern Iran. Research Journal of Environmental Sciences, 5, 836-840.
 Safford, L., Bjorkbom, J.C. and Zasada, J.C. (1990) Betula papyrifera Marsh. Paper Birch. In: Burns, R.M. and Honkala, B.H., Eds., Silvics of the Forest Trees of the United States, Agriculture Handbook-2, Washington DC.
 Bruschi, P., Vendramin, G.G., Bussotti, F.A. and Grossoni, P. (2000) Morphological and Molecular Differentiation between Quercus petraea (Matt.) Liebl. and Quercus pubescens Willd. (Fagaceae) in Northern and Central Italy. Annals of Botany, 85, 325-333.
 Xu, Z. and Zhou, G. (2008) Responses of Leaf Stomatal Density to Water Status and Its Relationship with Photosynthesis in a Grass. Journal of Experimental Botany, 59, 3317-3325.
 Pompelli, M.F., Martin, S.C.V., Celin, E.F., Ventrella, M.C. and Damatta, F.M. (2010) What is the Influence of Ordinary Epidermal Cells and Stomata on the Leaf Plasticity of Coffee Plants Grown under Full-Sun and Shady Conditions? Brazilian Journal of Biology, 70, 1083-1088.
 Royer, D.L. (2001) Stomatal Density and Stomatal Index as Indicators of Paleoatmospheric CO2 Concentration. Review of Palaeobotany and Palynology, 114, 1-28.
 Migalina, S., Ivanova, L. and Makhnev, A. (2009) Size of the Leaf as a Marker of Birch Productivity at a Distance from the Climatic Optimum. Russian Journal of Plant Physiology, 56, 858-862.
 Hughes, A.R., Stachowicz, J.J. and Willams, S.L. (2009) Morphological and Physiological Variation among Seagrass (Zostera marina) Genotypes. Oecologia, 159, 725-733.
 Kundu, S.K. and Tigerstedt, P.M.A. (1997) Geographical Variation in Seed and Seedling Traits of Neem (Azadirachta indica) among Ten Populations Studied in Growth Chamber. Silvae Genetica, 46, 2-3.
 Johnson, H.B. (1975) Plant Pubescence: An Ecological Perspective. The Botanical Review, 41, 233-258.
 Farley, R.A. and Mcneilly, T. (2000) Diversity and Divergence in Cistus salvifolius (L.) Populations from Contrasting Habitats. Hereditas, 132, 183-192.
 Nunez-Olivera, E., Martinez-Abaigar, J. and Escudero, J.C. (1996) Adaptability of Leaves of Cistusladanifer to Widely Varying Environmental Conditions. Functional Ecology, 10, 636-646.
 Dunlap, J.M. and Stettler, R.F. (2001) Variation in Leaf Epidermal and Stomatal Traits of Populus trichocarpa from Two Transects across the Washington Cascades. Canadian Journal of Botany, 79, 528-536.
 Ferris, R., Nijs, I., Behaeghe, T. and Impens, I. (1996) Elevated CO2 and Temperature Have Different Effects on Leaf Anatomy of Perennial Ryegrass in Spring and Summer. Annals of Botany, 78, 489-497.
 Li, W.L., Berlyn, G.P. and Ashton, P.M.S. (1996) Polyploids and Their Structural and Physiological Characteristics Relative to Water Deficit in Betula papyrifera (Betulaceae). American Journal of Botany, 83, 15-20.
 Camargo, M.A.B. and Maremco, R.A. (2011) Density, Size and Distribution of Stomata in 35 Rainforest Tree Species in Central Amazonia. Acta Amazonica, 41, 205-212.
 Russo, S.E., Cannon, W.L., Elowsky, C., Tan, S. and Davies, S.J. (2010) Variation in Leaf Stomatal Traits of 28 Tree Species in Relation to Gas Exchange along an Edaphic Gradient in a Bornean Rain Forest. American Journal of Botany, 97, 1109-1120.
 Körner, C. (1999) Alpine Plant Life: Functional Plant Ecology of High Mountain Ecosystem. Springer, Heidelberg.
 Hilaire, R.S. and Graves, W.R. (1999) Foliar Traits of Sugar Maples and Black Maples near 43°N Latitude in the Eastern and Central United State. Journal of the American Society for Horticultural Science, 124, 605-611.
 Dudley, S.A. (1996) Differing Selection on Plant Physiological Traits in Response to Environmental Water Availability: A Test of Adaptive Hypotheses. Evolution, 50, 92-102.
 Givnish, T.J. (1979) On the Adaptive Significance of Leaf Form. In: Solbrig, O.T., Jain, S., Johnson, G.B. and Raven, P.H., Eds., Topics in Plant Population Biology, Columbia University Press, New York.
 Lande, R. and Arnold, S.J. (1983) The Measurement of Selection on Correlated Characters. Evolution, 37, 1210-1226.
 Wade, M.J. and Kalisz, S.J. (1990) The Causes of Natural Selection. Evolution, 44, 1947-1955.
 Pearce, D.W., Millard, S., Bray, D.F. and Rood, S.B. (2006) Stomatal Characteristics of Riparian Poplar Species in a Semi-Arid Environment. Tree Physiology, 26, 211-218.