Environmental and developmental controls on specific leaf area are little modified by leaf allometry

1. Recent work shows that large leaves tend to require higher biomass investments per unit leaf area than small leaves. As a consequence, specific leaf area (SLA), which is a focus trait for a bulk of physiological and ecological research programs, is dependent on leaf size variation. Here, we address whether size dependency alters the outcome of research dealing with SLA responses to environmental or developmental change. 2. We compiled lamina mass (M) and surface area (A) data for 2158 leaves of 26 species, coming from studies investigating the reaction of SLA to variation in rainfall, growth-season length, light intensity, atmospheric CO₂, fire frequency, type of branch and leaf and plant age. We fitted the function M = α A ^β to the data of each experimental situation separately, and implemented a method to split SLA response as measured in the original study (SLA_Δm) into response due to leaf size dependency (SLA _Δa), and response due to treatment effects, after controlling for leaf size dependency (SLA_Δt). 3. The sign of the reaction did not differ between SLA_Δm and SLA_Δt. However, the magnitude of that response changed for most contrasts, though in variable ways. 4. Conclusions of past experiments hold, for the most part, after re-analysis including size dependency. However, given the large heterogeneity found here, we advise that future work investigating SLA be prepared to account for leaf size dependency when the factors under focus are suspected to alter leaf size.