Leaf trait variation captures climate differences but differs with species irrespective of functional group

Abstract

To clarify whether variation in leaf traits with climate differs with scale, i.e. across species and within a species, and to detect whether plant functional group affects species-specific response. Leaf dry matter content (LDMC), specific leaf area (SLA), mass- and area-based leaf N (Nmass, Narea) and leaf P concentrations (Pmass, Parea) and leaf chlorophyll concentration (SPAD) were measured for 92 woody plant species in two botanical gardens in China. The two gardens share plant species in common but differ in climate. Leaf trait variation between the two gardens was examined via mean comparison at three scales: all species together, species grouped into plant functional groups and within a species. A meta-analysis was performed to summarize the species-specific responses. At the scale of all species together, LDMC, SLA, Pmass and Nmass were significantly lower in the dry-cold habitat than in the wet-warm one, whereas Narea and SPAD showed an inverse pattern, indicating a significant environmental effect. The meta-analysis showed that the above-mentioned patterns persisted for SLA, Narea and SPAD but not for the other variables at the species-specific scale, indicating that intraspecific variation affects the overall pattern of LDMC, Pmass and Nmass and Parea. In terms of species-specific response, positive, negative or nonsignificant patterns were observed among the 92 species. Contrary to our prediction, species-specific responses within a functional group were not statistically more similar than those among functional groups. Our results indicated that leaf trait variation captured climatic difference yet species-specific responses were quite diverse irrespective of plant functional group, providing new insights for interpreting trait variability with climate.