Distribution of Functional Traits Along Climatic Gradients in the Subtropical Atlantic Forest

ABSTRACT Functional traits mediate resource acquisition and environmental tolerance, influencing community structure and ecosystem functioning. Here, we assessed the correlation between climatic factors and altitude with the spatial distribution of tree functional traits in the Subtropical Atlantic Forest (SAF). We compiled the information on tree communities in 83 inventories, assessing functional traits (spinescence, extrafloral nectaries (EFN), wood density, symbiotic fixation of nitrogen (SFN), deciduousness, leaf area, leaf border and leaf apex types) of 859 species and calculated the community‐weighted mean (CWM) trait values. We used the RLQ multivariate and fourth‐corner methods to relate the CWM to the climate variables and altitude. Deciduousness, SFN, leaves with toothed/serrated (not smooth) border, spinescence and leaf area were more significantly associated with climatic drivers. Spinescence and toothed leaf border were positively associated with colder and rainier regions. In turn, the occurrence of EFN increases with temperature seasonality. Deciduousness and SFN were mainly associated with higher diurnal and annual temperature ranges and isothermality. SFN is also correlated with precipitation seasonality. Larger leaf area values are associated with more favourable climates for carbon acquisition, that is, without extreme colder temperatures and lower temperature variation. The association between leaf deciduousness and SFN with daily and annual temperature variation may help to cope with abiotic conditions unfavourable to photosynthesis. In turn, to the extent that it is associated with hydathodes, toothed leaves are possibly important in hydric equilibria in cold and humid conditions. However, the association of spinescence with cold and rainy climates was unexpected. In the absence of severe aridity, the coldest climates are possibly the most limiting for primary productivity in the SAF, favouring conservative traits such as spines. The results suggest that the expression of traits in forest communities in southern Brazil is driven by climate, especially temperature variables, which may imply differences in ecosystem functioning in the region.