Resprouting is an effective strategy for persistence of perennial plants in habitats with disturbances such as fire. However, with changing fire regimes caused by climate change, what will limit the effectiveness of resprouting? We examined the effects of frequent fire and mowing on eight species of resprouting shrubs (three Quercus species, three ericaceous species (two Lyonia, one Vaccinium), and two palmettos (Sabal etonia, Serenoa repens) in Florida scrub through a factorial field experiment. We burned or mowed plots at four disturbance return intervals (DRI) – either annually, biennially, every three years, or once in six years (with all plots being burned in the sixth year to control for time-since-fire) – and examined growth responses of plants (height, estimated aboveground biomass, number of stems) based on sampling pre-treatment, and at six months, 1, 2, and 4 years post-treatment. We also measured starch concentrations in belowground parts before and after disturbances and soil properties one and two years post-disturbance to evaluate these factors as potential drivers of plant responses.
Results/Conclusions
Fire temperatures were hot (mean maxima varied from 414-698oC among burn days) and were typical of larger fires in Florida scrub. Plant biomass and heights were affected by DRI (being suppressed by frequent disturbance, especially initially) and varied among species. Disturbance type did not affect height dynamics. Biomass recovery varied among species. Biomass recovery in mown vs. burned treatments showed similar effects of DRI and similar trajectories over time. Numbers of stems were affected by DRI, disturbance type, and species. Stems increased after disturbances, then declined over time. Stem increases were greater with less frequent disturbances and with mowing. Carbohydrate concentrations varied among species and over time. Biomass at 6 months and 1 year post-treatment was related to affected by non-soluble non-structural carbohydrate concentrations, but the effect shifted from positive at six months to negative at one year. One-year post-disturbance, soil moisture and organic matter content were higher in mown plots, while pH was higher in burned plots. Soil properties were not affected by DRI. Given the slightly lower elevation of the mown plots, we interpret these differences as a site effect. Soil variables did not affect biomass responses. Although very frequent disturbances reduced growth responses, the magnitude of these responses was modest and the effects temporary. Because resprouting shrubs in Florida scrub appear resilient to a range of disturbance return intervals, frequent fire or mowing can be effectively used in restorations.