Fig. 5: Principal components analysis for Huber value (AS/AL), the ratio between leaf internal and ambient CO2 (ci/ca), Rubisco carboxylation capacity at 25° (Vcmax25), and potential specific conductivity (Kp) on species scale (each point represents a species, containing measurements from multiple individuals).
From: A test of ecophysiological theories on tropical forest functional traits along a VPD gradient

Values are transformed to achieve normal distribution but not standardized to equal variance; therefore, the length of arrows denotes the variance of the specific trait. The ellipses for each site are confidence ellipses around group mean points. The three panels display the same PCA, but with a different classification of scatter points. a The PCA without scatter points, but with labels for traits. b Scatter points according to study sites. c Scatter points according to phenology.