Fig. 4 Competitive interactions drive non-linear responses to ambient and added N. Estimated steady-state abundance distributions (relative plot proportions) for each species group across the observed gradients of ambient (left) and added (right) N deposition (zero centered +/- two standard deviations) in NW and W global change plots (See Fig S9 for all treatments). Points show simulated equilibrium abundances (100 at each value of x). Dotted lines show best model fit from a general additive model in the geom_smooth function in ggplot2 (Wickham 2009)..