Leaf functional traits of tropical forest plants in relation to growth form
We tested the generality of global leaf trait relationships among 44 tropical plant species from a broad array of growth forms (trees, lianas and understorey plants) in lowland Panama to determine how leaf trait relationships vary with whole-plant morphology within one site. We observed significant variation among growth forms for seven out of 10 leaf traits. Variation in leaf traits among growth forms was more pronounced per area than per mass. Thirteen bivariate leaf trait relationships that describe how plants allocate resources to photosynthesis were significant across all species. Growth forms showed distinct slopes, intercepts or shifts in the common slope for 12 of the 13 relationships. Trait relationships within trees and lianas showed good agreement with a global leaf trait data set. However, for understorey plants, trait relationships that included specific leaf area (SLA) deviated from the global data set, suggesting that understorey leaf-allocation patterns optimize SLA, and hence growth. Lianas showed lower values and rates of gas exchange than trees, and longer leaf life span for a given SLA, illustrating variation in leaf traits associated with growth form and canopy geometry. Functional variation in allocation to photosynthetic capacity among tropical forest species is related to microhabitat variations in light availability and whole-plant morphology among growth forms.