Specific leaf area correlates with temperature: new evidence of trait variation at the population, species and community levels

Abstract

Although specific leaf area (SLA) has been proposed to reflect plant responses to climatic changes, the link between SLA and temperature has never been systematically evaluated. Using in situ measured SLA values for 223 species occurring in 29 calcareous grasslands along a temperature gradient in the Bavarian Alps, we explored the SLA–temperature relationship at population (intraspecific), species (interspecific) and community level and investigated the relative impact of other environmental factors on SLA variation along the temperature gradient at the community level. Only 14 % of the studied species showed significant changes in their SLA values along the temperature gradient, despite high intraspecific variability of the SLA values. At the species level, we revealed a very weak positive SLA–temperature relationship (r2 = 0.04, p < 0.001). A very strong positive correlation between SLA and temperature was detected at the community level (r2 = 0.70, p < 0.001). In addition to temperature, disturbance also had a significant influence on trait variation at the community level. We conclude that the variation in SLA along the temperature gradient comes primarily from changes in the relative abundances of species, whereas the trait variation at the population and the species levels was affected by other environmental factors. We therefore recommend the use of community-weighted mean values in studies employing SLA–temperature relationships because they reveal more regular patterns than the underlying distribution of within- and among-site SLA values.