Figure 3.

Leaf phenolic concentration in birch leaves as a function of (a) temperature, (b) tree species richness and as a function of birch evolutionary distinctiveness (ED) for two contrasted levels of temperature under two contrasted levels of rainfall (c and d). The figure shows observed data (points) as well as model predictions (solid lines) and standard errors (shaded areas). ‘Warm’ and ‘cold’ temperature levels corresponded to 0.25 and 0.75 quartiles of the observed temperature range, respectively. ‘Low’ and ‘high’ rainfall levels corresponded to 0.25 and 0.75 quartiles of the observed rainfall range, respectively. The predictors that were not involved in the relationships shown were set at median values to compute predictions