Variability in recovery of cleared patches was investigated for 2 yr (from March 1991 to March 1993) in a low-shore habitat of geniculate coralline 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 grouped in 3 morphological groups: coarsely branched, filamentous and geniculate coralline algae. Cleared plots were small (7 x 7 cm), medium (12 x 12 cm) and large (22 x 22 cm), interspersed in areas of geniculate coralline algae at each of 2 different sites. Replicated clearings and controls were set up in March and September 1991. Seasonal patterns were particularly evident for the filamentous and the geniculate coralline algae, with peaks in abundance occurring in spring and summer for the former group and from September to December for the latter one. Algal colonization was variable in the experimental areas. All main factors (size, time of formation and location of patch) and some of the interactions significantly affected recovery of species, but patterns were specific for each group and were not consistent along the successional sequence. In general, differences due to size and time of formation 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 filamentous and coarsely branched algae, but only at determinate successional 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.
