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Florida scrub

Ecoregion of Florida, United States

  • 21 min read
  • 7 chapters

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Through Forest, Ecoregion and Sand

The ecosystem is endangered by residential, commercial and agricultural development. The largest remaining block lies in and around the Ocala National Forest. Lake Wales Ridge National Wildlife Refuge also holds a high proportion of remaining scrub habitat, while the Archbold Biological Station near Lake Placid contains about 20 km2 (7.7 sq mi) of scrub habitat and sponsors biological research on it.

Definition

Florida scrub is a community of xeromorphic species living on poor, well-drained soil, including some combination of sand pines, evergreen scrub oaks, Florida rosemary, rusty lyonia, and gallberry. Depending on conditions, scrubs may be dominated by saw palmetto, rusty lyonia, and gallberry; by Florida rosemary; by sand pines; or by some combination of evergreen oaks, including sandhill oak, sand live oak, Chapman oak, and myrtle oak. Independently of the number of sand pines present in a scrub, the shrub layer is consistently dominated by myrtle oak, sandhill oak, saw palmetto, sand live oak, Chapman oak, rusty lyonia and Florida rosemary. The scrub palmetto may also be present in scrubs on the Florida peninsula. While the shrub layer is usually dominated by oaks of varying density, some scrubs have a shrub layer consisting almost entirely of rosemary. Herbert John Webber noted that the sand pine is the most noticeable plant in large and moderate sized scrubs, but stated that the scrub oaks are probably more important in maintaining the scrub community.

Florida scrub is usually intimately associated with the longleaf pine sandhill or high pine ecoregion. High pinelands typically consist of longleaf pines, wiregrass, and other grasses, often with clumps or individual trees of deciduous oaks, such as turkey oak, present.

The term "scrub" may also cover plant communities in Florida called "sand pine scrub", "oak scrub", "rosemary scrub", "slash pine scrub", and "coastal scrub". Intermediate between scrub and associated habitats are "scrubby flatwoods" and "scrubby high pine". Some sub-types of Florida scrub are found outside of Florida. Myers notes that the "evergreen scrub forest" and "dune oak scrub" reported in southeastern Georgia cannot be distinguished from the oak and rosemary scrubs of Florida.

History

The Florida scrub is probably descended from the sclerophyllous Madro-Tertiary Geoflora. The geoflora spread along the Gulf of Mexico coast, and was widespread in Florida during the late Pleistocene. Near the end of the Pleistocene widespread rosemary scrubs in Florida were replaced by oak savannas, and then by sand pine scrubs. The range of scrubs in Florida contracted over the last 7,000 years as Florida's climate became more moist.

Florida scrub was probably first recognized as a distinct community by Charles Vignoles in 1823, although several naturalists working in the middle of the 19th century still did not do so. Scrub is usually intimately associated with the high pine ecoregion. While the two communities occur on the same poor soil (consisting almost completely of silica sand), they comprise completely different species, and the transition from one community to the other historically (prior to human intervention to suppress wildfire) was abrupt. Marjorie Kinnan Rawlings described the edge of the Big Scrub as "a vast wall, keeping out the timid and the alien."

Webber states that at the end of the 19th century a natural firebreak separated scrubs from high pine land. The grasses and other herbaceous plants of high pine land diminished near the boundary with scrub, and did not quite extend to the brush layer of a scrub. The near absence of plants in the transition zone meant that any grass fire that did reach the zone did not have enough intensity to ignite the evergreen plants of the shrub layer of a scrub. Webber observed that in 1935 the natural firebreaks seemed to be weakening, which he attributed to the encroachment of human civilization on the areas where scrubs are found.

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