Ecology 6th Edition by Charles Krebs

Exercise 11

In analysing the role of fire as a disturbance in tallgrass prairie, Collins et al. (1995) found that the intermediate disturbance hypothesis was supported if, instead of plotting fire frequency as in Figure 19.25b, they plotted time since the last fire on the x-axis. Why should they get different results for these two plots of the same data?
Reference Figure: 19.25b