South Florida flatwoods range vegetation responses to season of deferment from grazing

Abstract

Wiregrass (Aristida stricta Michx.)-dominated communities characterize extensive areas of South Florida that have been subjected to burning and uncontrolled grazing for decades. We evaluated the effects of deferment from grazing on species composition and herbage mass of these rangelands. Treatments were 1-ha exclosures that were closed to grazing December to March, closed April to July, closed August to November, always closed, or always open. All treatments were burned biennially. Herbage mass of preferred grasses was greater (P < 0.05) after 8 years in exclosures that were always closed (avg. 110 kg ha-1) compared with other treatments, which were not different (avg. 65 kg ha-1). Herbage mass of preferred grasses increased by 10 kg ha-1 year-1. Shrub biomass was greater in the treatment that was always closed (2,370 kg ha-1) compared with other treatments avg. 1,855 kg ha-1), and biomass increased quadratically over years. There were no effects due to treatments or years on biomass of wiregrass, other less desirable grasses, grasslike species, or forbs. Frequency of occurrence of preferred grasses was not affected by treatment and averaged 41%. Although preferred grasses were relatively abundant, neither their biomass nor frequency of occurrence increased on a scale relevant to management for cattle production when protected from grazing. This biennially burned, seasonally flooded, infertile wiregrass range is not highly responsive to grazing or deferment from grazing, hence responses may not justify the inputs required for more intensive grazing management.