Using Dry Prairies and Flatwoods for Rangeland and Livestock Grazing

History of Livestock Grazing in Florida

The persistence of dry prairie is closely tied to cattle ranching that has existed in central and South Florida since European settlement, and has continued to the present. The central Florida region was once sparsely populated (in comparison to other regions of Florida) and alternative land use options were scarce, thereby supporting management of native rangeland (DeSelm and Murdock 1993). Livestock have been present in dry prairie, and throughout central and southern peninsular Florida, for several hundred years (Yarlett 1985). Livestock grazing was historically (Harper 1921, Davis 1943) the primary economic benefit derived from the dry prairie/ flatwoods landscapes of central and south-central Florida (Moore 1974, Sievers 1985, Sullivan 1994). Harper (1927) reported that prior to the division of Desoto County into five counties the U. S. Census of 1900 indicated that Desoto County had 82,183 free-ranging cattle on 9,713 km² (3,750 mi²), about half of which was prairie. In 1920 there were 53,192 cattle in the county (over 95 percent beef cattle) and 70,459 cattle in 1925 (Harper 1927). Open, unfenced range existed in Florida until 1949 (Yarlett 1985). Between 1940 and 1960, many pastures of bahia grass (Paspalum notatum), digit grass (Digitaria sp.) and Bermuda grass (Cynodon dactylon) were established (Mozley 1985), as a result of land clearing and drainage alterations of native rangeland. By 1985, Florida had 1,215,000 ha (3 million acres) of perennial tame pasture and 405,000 ha (million acres) of annual tame pasture (Mozley 1985), an extensive area of which had formerly been dry prairie and flatwoods. In the early 1970s, production costs caused a shift towards native forage resources, although many ranchers had already recognized the value of native rangeland over improved pasture in the 1960s (Yarlett 1985). In 1984 there was a total cattle and calf inventory of 2.2 million head statewide (Yarlett 1985), with commercial cow-calf operations representing the major livestock production in Florida (Mozley 1985).

Forage Production

One reason Florida attracted such a large cattle industry is a growing season longer than 270 days and ample rainfall, ideal for growing forage and year-round use of native and improved pastures (Mozley 1985, DeSelm and Murdock 1993). Forage production for native rangeland (i.e. dry prairie and flatwoods) can range from 1,688 kg/ha (1,500 lbs/acre) on in-poor condition ranges to in excess of 8,438 kg/ha (7,500 lbs/acre) on in-excellent condition ranges, with the average production being from 4,500 to 6,750 kg/ha (4,000 to 6,000 lbs/acre) (Fults 1991, Sievers 1985, Mozley 1985). Hilmon and Hughes (1965) found that native rangelands burned in March or May produced a two-to-fourfold increase in forage, compared to those burned in October or November, with May burns causing Aristida beyrichiana to flower. However, native rangeland vegetation is not particularly nutritious for cattle, except immediately following a burn, with nutritional values rapidly declining thereafter (Hilmon and Hughes 1965).

Using Fire in Florida Rangelands

Native central and South Florida rangelands (i.e. dry prairies and flatwoods) are typically burned by ranchers annually or biennially during the winter or early spring months to stimulate forage growth, nutrition and palatability during the lean winter months (Abrahamson and Harnett 1990, Frost et al. 1986, Sullivan 1994). Ranchers also burn native pastures to maintain openness, reduce shrub cover, reduce fuel accumulations, and improve wildlife habitat (Abrahamson and Harnett 1990, Frost et al. 1986). However, frequent winter burning, when coupled with continuous grazing pressure, can lead to a decline in Schizachyrium stoloniferum (creeping bluestem, formerly Andropogon stolonifera) (White and Terry 1979), Sorghastrum secundum (lopsided Indiangrass), Amphicarpum muhlenbergianum (goobergrass), Andropogon virginicus var. glaucus (little chalky bluestem, formerly Andropogon capillipes), all of which are major preferred native forage grasses (Sievers 1985) that occur in dry prairie. Under such a management regime, Aristida beyrichiana (previously Aristida stricta, in part) (Hilmon and Hughes 1965) and saw palmetto are reported to increase (Sievers 1985), as well as other brush cover (Fults 1991). To lessen the impacts of grazing on rangelands with a previous history of frequent burning, some range managers have recommended burning on a 3-year cycle (Sievers 1985, Penfield 1985), which allows more opportunity for recovery in cover of preferentially grazed grasses.

Effects of Grazing on Prairie/Flatwoods Communities

Although the effects of fire and cattle grazing on the central Florida prairie/flatwoods communities have been examined (Hilmon and Hughes 1965, Sievers 1985, Fults 1991, Mozley 1985), there is a lack of knowledge on the effects of livestock grazing on various components of native prairie biodiversity. This is particularly true of most prairies outside of the Tallgrass Prairie region of the central United States. Herbivores preferentially feed on different plant species, consequently affecting dominance and relative abundance of plant species, thereby altering species composition (Howe 1994), with the potential to increase or decrease plant species diversity (Huntly 1991). Prolonged or severe preferential grazing can lead to colonization by ruderal plant taxa (Weaver 1968). In contrast, moderate grazing can result in greater species diversity relative to ungrazed sites, where a few species may dominate a community (Milchunas et al. 1988). Grazing activity may change the structure of the community by disrupting soil properties (Abrahamson and Harnett 1990) or by eliminating some life forms (Howe 1994). Furthermore, grazers may interact with other processes operating at different spatial and temporal scales, such as fire, drought, or other species interactions, resulting in scale-dependent effects (Harnett et al. 1996). Differences in livestock grazing management (i.e. year-round grazing, high intensity-short duration grazing, etc.) contribute to differences in vegetation responses (Harnett et al. 1996). Finally, historical ungulate assemblages were not confined, adding stochasticity to grassland development that is less evident in ungrazed prairies, small remnants, and fenced pastures (Howe 1994). All of these factors suggest that domestic livestock grazing, managed in different ways can produce significantly different effects on prairie community structure, species composition and prairie biodiversity (Hartnett et al. 1996). The effects of domestic livestock grazing on components of dry prairie biodiversity therefore have significant implications for management.