Examples of changes in stand productivity (mean annual increment: m3/ha/yr) in a lodgepole pine Douglas-fir stand from a montane spruce ecosystem. The response surfaces summarise the results of simulation runs with differences in root disease level, age at first entry (horizontal axis) and residual basal area (vertical axis). Contour lines in these plots connect combinations of residual basal area and entry age having the same first rotation MAI. Thick contour lines show integer levels of equal MAI, with thinner contour lines marking the 0.25, 0.50 and 0.75 levels between each integer value, as shown in the legend.