This study examined variation in leaf traits and water relations in 12 evergreen and semideciduous woody species that occur in both seasonal wet and dry forests in Costa Rica and compared intra-specific leaf-trait correlations to those found in inter-specific global studies. The following traits were measured in both forests across seasons for 2 years: leaf nitrogen (N), leaf carbon (C), specific leaf area (SLA), toughness, cuticle thickness, leaf thickness, and leaf lifespan (LLS). Leaf water potential (LWP) and water content (LWC) were measured as indices of plant available water. Canopy openness, soil moisture, and herbivory were also measured to compare environmental variation across sites. Although species contributed the greatest amount to variation in traits, season, forest, and their interaction had a large influence on patterns of intra-specific leaf-trait variation. Leaf traits that contributed most to variation across sites were C, LWP, leaf thickness, and SLA. Traits that contributed most to variation across seasons were leaf toughness, LWP, and LWC. Furthermore, leaf traits were more correlated (i. e., number and strength of correlations) in the dry than in the wet forest. In contrast to results from global literature syntheses, there was no correlation between LLS and N, or LLS and SLA. Both light and water availability vary seasonally and may be causing variation in a number of leaf traits, specifically those that relate to water relations and leaf economics. Strong seasonality may cause leaf-trait relationships at the local scale to differ from those documented in continental and global-scale studies.
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Acknowledgments This project was funded by an award from the Andrew Mellon Foundation to ML. We thank the Área Conservación Guanacaste (ACG) personnel, especially Maria Marta Chavarria, Roger Blanco, and Roberto Espinoza for logistical and taxonomic support. ACG also provided rainfall data for the dry forest. We thank Stroud Water Research Center for rainfall data in the wet forest (NSF LTREB grant, DEB 0516516). Andrey Castro, Roy Araya, Gilberto Araya, David Palma, Alexis Weintraub, Benigno Guadamuz, Hugo Guadamuz, and Julia Parks all provided valuable field assistance. We also thank Peter Reich, Massimo Pigliucci, R. Geeta, Elizabeth Leger, Susan Natali for thoughtful reviews on early versions of this manuscript.
- Intra-specific leaf-trait variation
- Light availability
- Tropical dry forest
- Water stress