Three important variables will determine the influence of defoliation:
Intensity
The intensity of defoliation can be defined as the proportion of the volume or mass of the aerial portion or leaves of the plant removed by defoliation. There is a close correlation between intensity and height of defoliation. The latter is generally used for practical purposes but is more applicable in grassveld than in Karoo bush or shrubveld.
Frequency
The frequency of defoliation is the number of times a plant is defoliated within a given period. It is usually expressed as the time between successive defoliations, e.g. every 2 months, or as the number of defoliations within a given period, e.g. twice per year.
Season
The season of defoliation has to do with the time of the year and the (growing) stage of the plant. There is usually a close correlation between the growth stage and the season but it depends on the steadiness of the climate.
Interactions are found between the intensity, frequency and season of defoliation. This means that the effect of defoliation, e.g. in summer or winter, may vary at different grazing intensities. When the effect of defoliation is therefore determined and discussed, all three of these variables must be carefully considered.