Burning more effective than mowing in restoring Florida scrub

Abstract

Exclusion of fire from pyrogenic ecosystems often results in changes in vegetation structure and the loss of biodiversity. Where landscape context constrains the application of fire, managers are applying mechanical treatments in conjunction with or as a surrogate for fire. We compared the effects of prescribed fire, mowing, mowing followed by fire, and a control at 2 fire-suppressed Florida scrub sites. Goals included increasing bare sand gaps, increasing endemic Florida scrub herbs, and reducing woody vegetation cover and height. We evaluated treatment effects on woody vegetation cover and height, ground cover (litter, lichens and bare ground), litter depth, and changes in the frequency and abundance of rare herbs prior to treatment and 1, 2 and 5 yr post-treatment. All treatments reduced woody vegetation cover and woody vegetation height relative to controls, and these effects often persisted for 5 yr post-treatment. In contrast, only treatments including fire resulted in consistent beneficial and long-lasting effects of increased bare sand cover, reduced litter and lichen cover, and reduced litter depth. Although the treatments had little effect on species composition and high variation made few comparisons statistically significant, burning (especially burning alone) increased occupancies and abundances of 2 rare species in some sites and in some years. In general, burning (with or without prior mowing) was more effective than mowing-alone or the control in restoring ground cover components and rare species populations. Fire provides unique benefits in the management of Florida scrub, and mechanical treatments are best used only when necessary to prepare sites for prescribed burning.