SOUTH FLORIDA FLATWOODS RANGE VEGETATION RESPONSES TO SEASON OF DEFERMENT FROM GRAZING

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 defe rment from grazing on species composition and herbage mass of these ra ngelands. Treatments were 1-ba exclosures that were closed to grazing December to March, closed April to July, closed August to November, al ways closed, or always open. All treatments were burned biennially. He rbage 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 ot her treatments, which were not different (avg. 65 kg ha-1). Herbage ma ss 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) co mpared with other treatments (avg. 1,855 kg ha-1), and biomass increas ed quadratically over years. There were no effects due to treatments o r years on biomass of wiregrass, other less desirable grasses, grassli ke species, or forbs. Frequency of occurrence of preferred grasses was not affected by treatment and averaged 41%. Although preferred grasse s were relatively abundant, neither their biomass nor frequency of occ urrence increased on a scale relevant to management for cattle product ion when protected from grazing. This biennially burned, seasonally fl ooded, infertile wiregrass range is not highly responsive to grazing o r deferment from grazing, hence responses may not justify the inputs r equired for more intensive grazing management.