Me. Gadd et al., Effects of simulated shoot and leaf herbivory on vegetative growth and plant defense in Acacia drepanolobium, OIKOS, 92(3), 2001, pp. 515-521
Plants have considerable ability to respond to herbivory, both with (above-
ground) regrowth and with increased defense. We simulated both leaf and sho
ot herbivory in controlled, replicated experiments on individuals of Acacia
drepanolobium in Laikipia, Kenya. These experiments were carried out on in
dividuals that had experienced different, experimentally controlled histori
es of large mammalian herbivory. Both forms of simulated herbivory were ass
ociated with compensatory regrowth. Branches whose shoots had been removed
grew significantly more over the next year than paired control branches, fu
lly compensating for the lost shoot length. Branches whose leaves were remo
ved both grew faster and had more leaves one year later than did control br
anches. Shoot removal, but not leaf removal, increased the production of si
de shoots. However, because past herbivore pressure was negatively associat
ed with net shoot growth, there may be a long-term cost of herbivory even w
hen plants appear to fully compensate for herbivory in the short term. In c
ontrast to the effects on growth, simulated herbivory did not significantly
increase physical (spines) or chemical (tannins) defenses, and there were
no significant negative correlations between compensatory growth and plant
defense.