Soil and Vegetation Geography of Florida's Coastal Zone

Introduction

A significant relationship exists between vegetation and soil: soil supports sufficient vegetation growth by providing moisture, anchorage, and essential nutrients, while vegetation serves as a protective covering for soil, safeguarding it against erosion and facilitating the maintenance of soil nutrition levels through nutrient cycling — that is, the accumulation of litter and its subsequent decay. Thus, soil and vegetation may be described as reciprocally interrelated. Vegetation is responsible for supporting essential ecosystem functions at multiple spatial scales.

Furthermore, vegetation strongly influences soil quality and attributes such as texture, volume, and chemistry, which in turn reciprocally impact several characteristics of vegetation, including floristic composition, productivity, and structure (Eni et al., 1). In this paper, the geography of coastal area vegetation and soil will be analyzed. Because considerable variation exists between different coastal areas — for example, the coast of Libya along the Mediterranean Sea is characterized by stones and a lack of any significant vegetation, whereas America's southeastern coast features coastal vegetation and sand — this paper will mainly address the Floridian coastal zone.

Coastal zone soils typically display a small degree of evolution, being affected by a fluctuating water table, depositional and erosional events, organic and carbonate matter, and spatial texture variability. Leaching, gleyzation, decarbonation, and brunification are identified as the significant soil-forming processes that occur within temperate-climate coasts (Bini et al., 31). Additionally, anthropic intervention facilitates soil development modification: water and sand extraction, tourism enhancement, terrain leveling, and land use modification all play a role under different environmental conditions, potentially influencing pedogenesis. Similarly, the natural vegetation of coastal regions may encounter change owing to evolving environmental conditions.

Soil geography involves soil variability and distribution on terrestrial sites, both locally and internationally. In this respect, of all soil formation elements, climate and vegetation — which functions as a directly dependent variable — chiefly determine soil geography. For the purposes of this paper, the two may be ideally perceived as linked variables. Other soil formation elements, such as time, parent material, and topography, can be considered secondary factors that alter the geographical regularities established by the climate–vegetation linked variable.

Drainage and Soils

Florida's flat landscape is characterized by as many as 1,700 streams — most of which can be found in the state's northwestern and northern parts — and several thousand lakes, primarily situated in central Florida. Florida also boasts one of the largest numbers of first-magnitude artesian springs in the nation, also primarily situated in central Florida. Apart from these, several drainage basins exist, with the largest being the Lake Okeechobee–Everglades basin (17,000 square miles, or 44,000 square kilometers). Lake Okeechobee (700 square miles, or 1,800 square kilometers) is the nation's third-largest freshwater lake, after Lake Michigan and Alaska's Iliamna Lake. This considerable water network draws its supply from the state's porous limestone substructure, which stores water in enormous quantities.

Floridian soils typically comprise clay, sand, muck, sandy loam, and peat; however, over three hundred kinds of soil have been identified in the region. Six broad soil zones can be described as follows:

(1) Flatwood lowland soil: Found in the state's most significant soil zone, corresponding to the lowland coastal region. The area is characterized by level terrain underlaid with a hardpan that hampers drainage and simultaneously encourages flooding. (2) Organic soil: Found in several areas of the state, especially the Lake Okeechobee–Everglades basin. It is waterlogged, with submergence usually preventing the oxidation, shrinkage, and decay of muck and peat; nevertheless, drainage of the soil is followed by swift deterioration. (3) Southern limestone soil: Found in the Big Cypress Swamp, the Miami–Homestead region, and the Kissimmee Valley. (4) Northern slope soil: Typically regarded as a separate area, it is situated immediately to the south of the northern upland zone. (5) Northern upland soil: Ranging from well-drained loam to dry sand, this type of soil is found across northern Florida. (6) Central upland soil: Found in central Florida's higher-ridge regions, west of the Apalachicola River. Several other soil zones also exist in the state, including swamps extending into interior Florida and dunes lying at the fringes of its beaches.

Geological and Physiographic Setting

The Floridian Peninsula's east coast is subaerially situated over a considerable carbonate platform comprising a dense sedimentary sequence traceable to Mesozoic (Jurassic) and Cenozoic (Miocene) ages — roughly between 180 and 5 million years ago (Benedet et al., 360–365). According to regional research, the calcium carbonate concentration of Florida's Atlantic beaches reaches as high as 55 percent by weight (for instance, at Cocoa Beach), and several Floridian beaches have more than 40 percent carbonate content, or less than 60 percent siliciclastics (Benedet et al., 360–365). This high concentration of calcium carbonate in beach sediments has mainly been attributed to elevated carbonate production in warm local waters.

Average near-shore sediment grain size increases as one moves from the northern beaches to those in the south, accompanied by an increase in calcium carbonate content and a decrease in siliciclastic content — ranging from 0.20 mm in Volusia County to 0.4 mm in Miami-Dade County at 100 meters from the shore. Coarser values in the southern region can reach 0.7–0.9 mm on account of shell fragmentation (Benedet et al., 360–365). Anastasia Formation bedrock is either exposed above or buried below the surface, though at only 2–3 meters depth in the case of native berms. The dunes fronting the state's back beaches have mostly been leveled to allow for the construction of high-rise buildings. As a result, incipient dunes can now only form in areas where infrastructure or buildings are constructed far from the seashore. Seawalls impede dune formation in several back beaches along these developed shorelines.

Florida Coastal Vegetation

Florida's sandy coastal zones feature a heterogeneous environment owing, in part, to geomorphological diversity. Various landforms may be observed, and the flora growing within them are influenced to a large extent by oceanicity — that is, the impact of the ocean on adjacent continental areas (Psuty et al., 314–25). What results is a varied assortment of vegetation. In addition to a range of factors stemming from the oceanic presence (such as wind velocity and salt spray), a temporal gradient also exists in substrate age, increasing toward the interior (Araujo and Pereira). Along broader coastal plains, this high gradient may not appear continuous as one moves inland, owing to the presence of landforms such as rivers, lagoons, and estuaries, either present or former.

Closer to the ocean, sandy deposit flora communities commonly display a clear zonation pattern that may be subdivided into an outer pioneer area and an interior dense coastal copse. Flora communities found further inland may not always follow a linear strand plain or dune field sequence (Araujo and Pereira), but they are nonetheless found along a gradient of greater community complexity — that is, greater species richness, biomass, height, and cover.

The southernmost end of the Floridian Peninsula and its nearby coastal regions constitute the nearest land areas of continental America to the Tropic of Cancer, and are consequently characterized by near-tropical climates as well as coastal and geological characteristics shared with those of the Caribbean basin. The region north of the Florida Keys is generally considered "subtropical," reflecting a climate with tropics-like temperatures but occasionally experiencing below-freezing temperatures of ecological significance (Armentano et al., 226). As the Florida Keys region seldom sees temperatures below 5°C, it may be regarded as a tropical area.

While the majority of natural landforms of Florida's southeastern coast are made up of grass- and sedge-dominated freshwater wetlands of the Northern Temperate flora, sufficiently large regions are also occupied by West Indian and temperate flora. The woody communities of the Floridian coastal region may be grouped into three classes depending on substrate and species composition: tree isles on shell, peat, or marl deposits found on limestone outcrops; various kinds of extensive swamp forests; and pinewoods on limestone outcrops.

The term tree isle has been used by most authors to refer to small woody vegetation areas embedded within a landscape of a different vegetation type (Armentano et al., 225–281). The "matrix" in which these islands occur may be freshwater or mangrove swamp, Rockland pinewood, or brackish or freshwater marsh. The substrate of tree islands is typically different from that of the adjoining vegetation. Thus, in the Taylor and Shark Sloughs freshwater sawgrass marshlands of Everglades National Park (ENP), tree isles may be found on limestone or wooded peat ridges within a region of peat or freshwater marl (calcitic mud). In coastal areas, hardwood hammocks may be found on sand outcrops, marl, or anthropogenic midden deposits within marine clay or mangrove peat zones. In slash pinewoods on Long Pine Key (ENP) and Big Pine Key (lower Florida Keys), hardwood hammocks appear on raised limestone ridges. In all instances, roots occupy a fine surficial layer of coarse, unsaturated organic matter.

Two significant tree isle classes differ from one another based on key controlling elements and prevalent flora. Tropical hardwood hammocks are found almost invariably on well-drained soils and rocky ridges, and are rich in species with tropics-centered distribution ranges. Tropical hammocks also form the predominant cover of some remaining undeveloped upland regions of the Florida Keys. Swamp forests mostly comprise species with temperate area-centered distributions, adapted to poorly-drained soils. They may occur as small distinct stands or as parts of larger tree isles — including hammocks on ridges — and experience regular flooding that results in peat soil formation. Swamp forests may also appear as widespread temperate hardwood or Taxodium stands that dominate landscapes or form savannahs with a graminoid ENP or BCNP understory; however, these are not considered tree islands.

Conclusion

In the context of coastal physical processes, sediment budget and human manipulation of coastal topography are perhaps underrated and considered minor disturbances on the instantaneous or Holocene timescale. However, several modern applied coastal geomorphology problems operate on the decadal-to-centurial timescale, which is directly relevant to human concerns and influenced by human activity. Understanding human impacts and likely changes at this temporal scale has therefore been linked to the identification of robust feedback relationships between physical processes, ecological communities, and human intervention along dynamic coastlines such as those of Florida.

Works Cited

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