Fire-frequency effects on vegetation in north Florida pinelands: Another look at the long-term Stoddard Fire Research Plots at Tall Timbers Research Station

The Stoddard Fire Plot study at Tall Timbers Research Station near Tallahassee, FL, ongoing since 1960, is one of several long-term studies of fire frequency in the southeast Coastal Plain, USA. Previous data and publications from the Stoddard Fire Plots supported a saturation model of fire frequency effects. According to this model, vascular plant species richness increases along with fire frequency but only up to a threshold determined by woody overstory competition. Beyond the threshold, further increases in fire frequency have little additional impact on species richness or understory vegetation composition. Prior analyses suggested this threshold to occur at ∼6–7 year burn intervals. In this paper we present more recent data from this same long term study that are not consistent with the “Saturation Hypothesis” as originally formulated. These results indicate (1) “saturation” of canopy (>2.0 m) cover at 3 year burn intervals rather than the predicted 6–7 years, (2) small-scale (⩽1.0 m) species richness positively associated with fire frequency across a gradient of short-interval fires from 3- to 1-year, (3) statistically significant species composition (cover and abundance) shifts across this same short-interval fire frequency gradient, with greatest herbaceous dominance associated with 1- and 2-year burn treatments. Prescribed burners influenced by the earlier results might wish to consider reducing the interval between fires.

► We evaluate two hypotheses of fire frequency impacts on southern pine vegetation.
► Our results support a most frequent fire hypothesis of pineland ecosystem management.
► Scale was important for evaluating vascular plant species richness impacts.
► Fire frequency effects on species richness were not significant at 10 m2 or greater.
► Composition shifted from herbs to woody across the 1–4 year range of fire intervals.