154—South-Central Florida Ridge

This MLRA (shown in blue in the figure above) is entirely in Florida. It makes up about 8,285 square miles (21,470 square kilometers). Parts of the east side of the city of Tampa Bay and the west half of Orlando are in this area. Interstate 75 parallels the north-south axis of the northern half of this MLRA, and Interstate 4 crosses the southern tip. The Ocala National Forest and the Withlacoochee State Forest are in this area.

Physiography

This area is in the Floridian Section of the Coastal Plain Province of the Atlantic Plain. The area is nearly level to gently rolling. The land surface is very irregular because of the many sinkholes that dot the area. Elevation is 80 to 165 feet (25 to 50 meters) in most of the area. It ranges from sea level along a narrow strip on the western edge of the area to 330 feet (100 meters) on some hills.

The extent of the major Hydrologic Unit Areas (identified by four-digit numbers) that make up this MLRA is as follows: Peace-Tampa Bay (0310), 46 percent; St. Johns (0308), 36 percent; Southern Florida (0309), 14 percent; and Suwanee (0311), 4 percent. The Withlacoochee River is in this area.

Geology

This area is a young marine plain underlain by Tertiary-age rocks, including very fine grained shale, mudstone, limestone, and dolomite beds. A sandy marine deposit of Pleistocene age overlies the limestone in most of the area. Phosphate is mined from the limestone beds in the central part of the area.

Climate

The average annual precipitation in this area is 46 to 56 inches (1,170 to 1,420 millimeters). About 60 percent of the precipitation occurs from June through September. Most of the rainfall occurs as moderate-intensity, tropical storms that produce large amounts of rain from late spring through early autumn. Late autumn and winter are relatively dry. The average annual temperature is 68 to 73 degrees F (20 to 23 degrees C). The freeze-free period averages 335 days and ranges from 300 to 365 days.

Water

Following are the estimated withdrawals of freshwater by use in this MLRA:

Public supply—surface water, 3.0%; ground water, 34.9%
Livestock—surface water, 0.1%; ground water, 0.7%
Irrigation—surface water, 9.8%; ground water, 23.8%
Other—surface water, 8.2%; ground water, 19.5%

The total withdrawals average 1,220 million gallons per day (4,620 million liters per day). About 79 percent is from ground water sources, and 21 percent is from surface water sources. Rainfall and surface and ground water sources provide an abundance of water. Many lakes are in the sinkholes throughout the area, but the area has few perennial streams. The risk of ground-water contamination is high because of the high water table and the karst topography in this area.

Almost all domestic, municipal, and irrigation water is obtained from wells in the Floridan aquifer in this MLRA. This aquifer is one of the most productive ground water sources in the United States. The water is hard but is of good quality. Wells yield large quantities of calcium bicarbonate type water. The Floridan aquifer is a thick sequence of Tertiary limestone and dolomite. The Eocene Avon Park Formation and Ocala Limestone are the thickest and most productive units in the aquifer system.

Soils

The dominant soil orders in this MLRA are Entisols and Ultisols. The soils in the area dominantly have a hyperthermic soil temperature regime, a udic soil moisture regime, and siliceous mineralogy. They generally are very deep, excessively drained to somewhat poorly drained, and loamy or sandy. Paleudults (Arredondo, Millhopper, and Sparr series) formed in loamy marine sediments on uplands. Quartzipsamments (Astatula, Candler, Lake, and Tavares series) formed in mixed sandy eolian and marine sediments on uplands.

Biological Resources

This area supports “sand hill” vegetation. Turkey oak, bluejack oak, and longleaf pine are the major species. Running oak, gopher apple, and such grasses as bluestems and panicums characterize the understory.

Some of the major wildlife species in this area are deer, feral hog, fox, raccoon, rabbit, gray squirrel, fox squirrel, turkey, bobwhite quail, and dove. The species of fish in the area include largemouth bass, shellcracker, catfish, bluegill bream, and crappie.

Land Use

Following are the various kinds of land use in this MLRA:

Cropland—private, 7%
Grassland—private, 23%
Forest—private, 28%; Federal, 4%
Urban development—private, 23%
Water—private, 7%; Federal, 2%
Other—private, 6%

The agricultural enterprises in this area include the production of livestock, citrus, and truck crops. Forest products also are important. The forested areas include the Ocala National Forest. Pulpwood is the chief forest product, but some lumber also is produced. Some of the forests are grazed. Although less than one-tenth of the acreage is used for crops, this is the major citrus-producing area in Florida. Many kinds of winter vegetables also are grown. About half of the pastured areas in the MLRA are improved and intensively managed. Beef cattle are the principal kind of livestock, but dairying is an important enterprise near some of the large cities. Urban land makes up a large acreage in the area. Phosphate mines are a prominent feature in the central part of the area.

The major soil resource concerns are wind erosion, maintenance of the content of organic matter and productivity of the soils, and management of soil moisture. Additional resource concerns are water quality, water quantity (excess amounts), and plant and animal productivity and health.

Conservation practices on cropland generally include conservation crop rotations, cover crops, irrigation water management (including microirrigation systems), nutrient management, and pest management. Conservation practices on pasture and rangeland generally include prescribed grazing, brush management, pest management, prescribed burning, and watering facilities. Conservation practices on forestland generally include forest stand improvement, forest site preparation, prescribed burning, firebreaks, establishment of trees and shrubs, pest management, and management of upland wildlife habitat.

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