define Z according to species- area relation equation S= CAz .
In the given equation, Z = Slope of the line (regression co-efficient). Regression coefficient, Z is defined as the slope of the line in the graph which is plotted for species richness versus area. Larger is the area, steeper will be the plot.
Value of Z is found to lie in the range of 0.1 to 0.2 for comparatively smaller areas such as countries while for very large areas such as entire continents, the slope of the line is much steeper with Z value lying from 0.6 to 1.2.