Environmental and Experimental Botany 87 (2013) 110–119 Contents lists available at SciVerse ScienceDirect Environmental and Experimental Botany journa l h o me pa g e: www.elsevier.com/locate/envexpbot Differences in the leaf functional traits of six beech (Fagus sylvatica L.) populations are reflected in their response to water limitation David Sánchez-Gómez a,∗ , T. Matthew Robson b , Antonio Gascó a,c , Eustaquio Gil-Pelegrín d , Ismael Aranda a,∗ a Centro de Investigaciones Forestales (CIFOR), Instituto Nacional de Investigaciones Agrarias (INIA), Carretera de la Coru˜ na km 7,5, 28040 Madrid, Spain b University of Helsinki, Department of Biological and Environmental Sciences, FIN-00014 Helsinki, Finland c IE University, Bachelor in Biology, Segovia Campus, Cardenal Zú˜ niga 12, 40003 Segovia, Spain d Centro de Investigación y Tecnología Agroalimentaria, Unidad de Recursos Forestales, Zaragoza 50080, Spain a r t i c l e i n f o Article history: Received 9 February 2012 Received in revised form 17 September 2012 Accepted 27 September 2012 Keywords: Climate change Gas exchange Intraspecific variability Nitrogen content Photochemical efficiency Photosynthesis Specific leaf area Stomatal conductance Water-use efficiency Water stress a b s t r a c t Patterns of intraspecific variation in functional traits have been widely studied across plant species to find out what general suites of traits provide functional advantage under specific environmental conditions. Much less is known about this variation within tree species and, in particular, about its relationship with performance variables such as photosynthetic rates under water deficit. Nevertheless, this knowledge is fundamental to understand the adaptive potential of drought sensitive tree species to increased aridity as predicted in the context of climate change. Intraspecific variation in photosynthetic performance and other leaf functional traits in response to water availability were examined in a glasshouse experiment using seedlings of six European beech populations. The physiological response of seedlings to a “water stress” treatment was compared to a “control” treatment along an experimental cycle of progressive soil water deficit and recovery. We found evidence of intraspecific variation in beech’s photosynthetic performance and other leaf functional traits in response to water availability. We also detected intraspecific variation in leaf-level tolerance of water deficit and phenotypic plasticity to water availability suggesting a pattern shaped by both regional and local scale effects. The Swedish population was particularly sensitive to water deficit, being the only population showing impaired photochemical efficiency under the experimental water deficit. Leaf-level tolerance of water deficit was related to PNUE, but not to other functional traits, such as WUE, SLA or leaf nitrogen content, that have been described to vary across species in adaptation to drought tolerance. Our results support the idea that general trends for variation in functional traits across species do not necessarily reflect a similar pattern when observed at the intraspecific level. The observed functional variation between beech populations reaffirms the importance of local adaptation to water deficit in the context of climate change. © 2012 Elsevier B.V. All rights reserved. Abbreviations: ı 13 C, carbon isotope composition; ФPSII , effective quantum effi- ciency of PSII; Amax, area-based maximum photosynthetic rate; Ammax, mass-based maximum photosynthetic rate; GLM, general linear model; gs , stomatal conduc- tance; Na, area-based nitrogen content; Nm, mass-based nitrogen content; PCA, principal components analysis; PNUE, photosynthetic nitrogen-use efficiency; PPFD, photosynthetic photon flux density; S in , water to be added to seedling i at measure- ment point n; SLA, specific leaf area; T i , different time points along the experiment; VWCs , soil volumetric water content; W in , pot weight for seedling i at measurement point n; W ti , Expected pot weight for seedling i when target VWCs is reached; WC in , pot weight for seedling i at measurement point n; WUE i , instantaneous water-use efficiency. ∗ Corresponding authors. Tel.: +34 91 347 6857; fax: +34 91 347 6767. E-mail addresses: david.sango@gmail.com (D. Sánchez-Gómez), aranda@inia.es (I. Aranda). 1. Introduction The study of patterns of variation in plant functional traits along environmental and resource gradients is fundamental to under- stand ecological (Grubb, 1977; Silvertown, 2004; Westoby and Wright, 2006) and evolutionary processes (Ackerly et al., 2000). Most studies of variation in functional traits have been focused on interspecific rather than intraspecific differences (Fajardo and Piper, 2010). However, an increasing number of studies, since the pioneering work of Mooney and Billings (1961), have highlighted the ecological importance of intraspecific variation in functional traits of forest tree species (Arntz and Delph, 2001; Benowicz et al., 2000; Brendel et al., 2008). Intraspecific phenotypic variation across the geographical dis- tribution range of a species can result from phenotypic plasticity, 0098-8472/$ – see front matter © 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.envexpbot.2012.09.011