Fig. 1. Two- (a) and three-dimensional (b) representation of threshold dynamics and regime shifts in time and space. Shifts from regime 1 to regime 3 have been measured as an increase or decrease in mean and variance of vegetation (and soil) response (a, Washington-Allen et al. 2006, 2008, and 2009). Regime shifts translate to three dimensions with the addition of drivers that induce either discrete (A through D) or continuous (E and F) change in response variables (b).