Fig. 6From: Tree species richness enhances stand productivity while stand structure can have opposite effects, based on forest inventory data from Germany and the United States of AmericaEffects of location (a), climate (b), and stand density and tree species richness (c) on tree size heterogeneity of German inventory plots. Yellow = positive effect on productivity, red = negative effect on productivity. Blue contour lines show where the function has a constant valueBack to article page