Effect of intensity and frequency of defoliation on aerial growth and carbohydrate reserve levels in Acacia karroo plants.

Abstract

Acacia karroo trees were defoliated by goats at two intensities and four frequencies; 2, 4, 8 and 12-weekly. Leaf accumulation and carbohydrate reserve levels were compared to a non-defoliated control, and to plants (defoliation controls) which were defoliated for the first time that season each time a frequency treatment was defoliated. These plants are activated by defoliation in such manner that successive defoliations can result in this activation being additive. There is clearly a defoliation level below which they are not activated. Activation appears to be negated to a degree by defoliations at 2 and 4-weekly frequencies, relative to the 8-weekly defoliation frequency. The 12-weekly frequency at heavy defoliation produces less than the same defoliation at 8-weekly frequency. The 2-weekly frequency treatments produced as much leaf as the 4 and 12-weekly defoliations at the same defoliation intensity. The more frequently plants were defoliated, the more carbohydrate reserves dropped. However, plants adjusted to cope with very frequent defoliations. There was no connection between leaf accumulation and carbohydrate reserve levels following the different frequencies and intensities of defoliation.

Keywords: acacia karroo; botany; browse; carbohydrate; compensatory growth; defoliation; defoliation frequency; frequency; frequency of defoliation; goats; leaves; trees