Gaps, landscape patches with distinct vegetation structure lacking normal dominant plants, can support high diversity and specialist species. In Florida rosemary scrub, previous research showed indistinct gap size patterns with fire and the dependence of certain species on gaps. We re-sampled many of these gaps in 2011-12, 8-9 years after the initial sampling in 2003, sampling vascular plant and ground lichen occurrence by species, gap size, and burn history in 691 gaps. We analyzed gap, vegetation, and species dynamics using descriptive methods and mixed models.
Results/Conclusions
In 2011-12, gap sizes declined in a regular logarithmic pattern with time-since-fire, suggesting a rapid decrease in gap size during the first ten years, and decreasing decreases in gap size thereafter. Between 2003 and 2011-12, unburned gaps usually remained extant or split, whereas burned gaps usually merged. Unburned gaps and split gaps tended to shrink while burned gaps and merged gaps became larger. Species richness strongly increased with gap size and was higher in burned gaps in 2011-12; there was a positive interaction between gap size and burning on species richness (mixed model). Merged gaps were richer than split or extant gaps. Over time, unburned gaps lost richness while burned gaps gained. Accounting for species richness across pre-merge gaps, gap merging increased richness. Accounting for species richness across post-split gaps, splitting did not decrease composite richness. Individual species had various patterns across time with and without fire. Ground lichens tended to disappear from burned gaps, but many herbaceous species that are known to be killed by fire increased occupancy in burned gaps. Dominant shrubs often had stable patterns with and without fire. Gap size in 2003 was often associated with gains in occupancy. Time-since-fire in 2003, dominant shrubs in gap edges, and the change in gap area over eight years had little effect on most species.