Effects of simulated shoot and leaf herbivory on vegetative growth and plant defense in Acacia drepanolobium

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.