Canopy Gaps as Foci of Succession in a Florida Keys Tropical Hardwood Forest

Canopy gaps in many forests are thought of as resetting the successional sequence due to increased light availability. In this study, canopy gaps were identified with a LiDAR digital canopy model in a Key Largo hardwood forest. Sapling structure and composition were recorded in the gaps. Weighted averaging calibration was applied to relative abundances of trees to determine the successional age optimum for each tree species, and weighted averaging regression was used to calculate inferred stand ages for each gap’s saplings. The inferred stand ages were greater in young forest gaps than in surrounding, unimpacted forest, suggesting that succession was actually advanced. Canopy heights in Key Largo were shorter than many other tropical and temperate forests, canopy gaps were smaller and therefore light availability did not vary with gap area. This suggests that the largest gaps may not be big enough to produce the light conditions required to reestablish pioneer tree species. Soil and water conditions in young forest gaps may also favor mature rather than pioneer species. Resetting of the forest successional sequence may not occur without intense disturbances such as fires or major hurricanes that remove the entire canopy and consume or erode soils.