EFFECTS OF COMPETITION AND DISTURBANCE ON THE RESPROUTING PERFORMANCEOF THE MEDITERRANEAN SHRUB ERICA-MULTIFLORA L (ERICACEAE)

Two field experiments were designed to evaluate the importance of comp etition, fire, repeated disturbance, and their interactions on the veg etative and reproductive performance of the Mediterranean shrub Erica multiflora over a 2.5-yr period. In a burn experiment, fire was applie d to the ground-level stumps of previously clipped 13-yr-old plants wi th a propane torch and competition was diminished by removal of neighb oring plants. Fire resulted in a reduction of sprout vigor and biomass of flowers; mature neighbors also reduced E. multiflora sprout vigor and flowering. The interaction between fire and competition was nonsig nificant. In a stand burned by a wildfire we studied the effects of re generating neighbors on target plants by removing all neighbors or onl y Quercus coccifera. the most dominant species in the burned stand. In this stand we also simulated herbivory by repeatedly clipping the spr outs of E. multiflora. Regenerating neighbors did not affect target pl ant sprout vigor after the wildfire, but did cause a decrease in the b iomass of flowers per plant. Survival decreased after repeated clippin g but was not affected by neighborhood treatment. The results suggest that the importance of competition on resprouting vigor was temporally variable. Variables related to plant size rather than species determi ned competitive superiority: resprouting neighbors did not affect resp routing performance of target plants, but mature neighbors did. In nat ure, fire may directly reduce vegetative and reproductive biomass by t he heating effect. But it may have an indirect positive effect on biom ass, by reducing competition among plants. Frequent disturbances that removed aboveground biomass of E. multiflora had a detrimental effect on target plant survival independent of neighborhood effect.