RECOVERY OF PATCHES IN AN ASSEMBLAGE OF GENICULATE CORALLINE ALGAE - VARIABILITY AT DIFFERENT SUCCESSIONAL STAGES

Variability in recovery of cleared patches was investigated for 2 yr ( from March 1991 to March 1993) in a low-shore habitat of geniculate co ralline algae on the west coast of Italy. A 3-way factorial experiment was used to assess the effects of size, time and location of patch on algal colonization in experimentally cleared plots. Species were grou ped in 3 morphological groups: coarsely branched, filamentous and geni culate coralline algae. Cleared plots were small (7 x 7 cm), medium (1 2 x 12 cm) and large (22 x 22 cm), interspersed in areas of geniculate coralline algae at each of 2 different sites. Replicated clearings an d controls were set up in March and September 1991. Seasonal patterns were particularly evident for the filamentous and the geniculate coral line algae, with peaks in abundance occurring in spring and summer for the former group and from September to December for the latter one. A lgal colonization was variable in the experimental areas. All main fac tors (size, time of formation and location of patch) and some of the i nteractions significantly affected recovery of species, but patterns w ere specific for each group and were not consistent along the successi onal sequence. In general, differences due to size and time of formati on of patch decreased as succession proceeded, but some exceptions to this trend were also evident. The abundance of coarsely branched algae , for example, was greater in large than in medium gaps after 15 mo of recovery. Differences among sites were particularly evident for the f ilamentous and coarsely branched algae, but only at determinate succes sional stages. In addition, temporal trends were not the same for the 2 groups of plants. Spatial patterns were more evident at mid and late successional stages for the former group, whilst the reverse occurred for the latter. Overall, these results suggest caution in contrasting deterministic and nondeterministic views of community dynamics.