SPROUT RECRUITMENT AND SELF-THINNING OF ERICA-MULTIFLORA AFTER CLIPPING

Regrowth after clipping and the effect of local competition were studi ed in a natural population of Ei icn multiflora in a Mediterranean shr ubland, by removing neighbours at 1 and 2 m around the target plants d uring four growing seasons. Removal of surrounding natural vegetation increased the number, the density (number of sprouts per stump area) a nd the biomass of the sprouts growing from clipped plants. Target plan ts only interacted with their near neighbours. Target plants had a neg ative relative increment in the number of sprouts per stump during the 18 months immediately following treatment, but a positive increment t hereafter, which suggests that there was a constant or episodic recrui tment of sprouts within the stump after clipping. Competition treatmen t had a non-significant effect on the negative increment of sprouts pe r stump. The self-thinning trajectory was different for the different competition treatments: there was an allometric negative relationship between density of sprouts and mean biomass of survivors during all sa mpling periods in genets without neighbours in a 1-m radius; the self- thinning trajectory of sprouts in genets without neighbours in a 2-m r adius was short, a net increase in sprouts per stump area was accompan ied by an increase in mean sprout biomass 30 months after clipping. Du ring the same period, however, plants with neighbours showed a decline in both the sprout biomass and density.