Description The pine rocklands are a
critically imperiled ecosystem located in
southern Florida, the
Bahamas,
Turks and Caicos Islands, and
Cuba. Its location in south Florida and throughout the Caribbean Archipelago straddles the southern and northern ends of the
temperate and
tropical flora ranges, respectively. This helps explain why the pine rocklands are home to a wide variety of plants and animals, many of which are
endemic to Florida, south Florida, or the pine rockland itself. It is characterized by an open
canopy of South Florida slash pine (
Pinus elliotti var. densa), a patchy subcanopy of palms and shrubs, and an extremely diverse
herbaceous layer, growing atop
Miami oolitic limestone.
Distribution In south Florida, pine rocklands occur in
Miami-Dade County,
Monroe County, the
Lower Keys,
Everglades National Park, and
Big Cypress National Preserve, but can also be found throughout the
Caribbean Archipelago. Despite its range, the pine rocklands are limited in distribution. The remaining
fragments scattered across the county are protected as public parks or
Environmentally Endangered Lands and range in size from 0.1 ha to 324 ha, with the average size being 6 ha and the median being 1.7 ha. The Long Pine Key portion in Everglades National Park still holds around 9915 ha, or 80% of all pine rockland found in Florida.
Physiography The pine rocklands in Miami-Dade County and Everglades National Park are found on
limestone substrates along the
Miami Rock Ridge, an exposed
oolitic limestone matrix 2–7 meters above sea level that extends from northern Miami to the southern Everglades with
disjunct sections in the Lower Keys. However, the hydrology of south Florida has changed drastically since the 1950s due to urban expansion and increased agricultural practices. The limestone of the Miami Rock Ridge was perfect for development, and subsequent drainage has led to a significant decrease in the water table. A lowered water table may harm sites prone to seasonal flooding and may increase the risk of salt-water intrusion. The Comprehensive Everglades Restoration Plan is an attempt to restore the hydrology of the Everglades.
Flora ,
Big Pine Key The south Florida pine rockland is unique geographically. Southern Florida is located at the southern end of the temperate
North American Floristic Region and at the northern end of the tropical
Caribbean Floristic Region. This location allows for the mixture of vegetation from two distinct areas at the extremes of their ranges. Around 9% of all pine rockland plants found in Miami-Dade County alone are endemic to Florida, and around 14 taxa are endemic to the Miami-Dade pine rockland itself. Overall, there are over 537 plant species found throughout the south Florida rocklands. Pine rocklands are defined by an open canopy of South Florida slash pine with heights ranging from 20–24 meters, but can be less due to past disturbance. Many sites were logged extensively in the early 1990s reducing slash pine coverage and killing understory vegetation. Subsequent plantings in the late 1980s led to many even-aged stands with different stand densities. The subcanopy is dominated by a variety of palms and tropical hardwoods, depending on the location, substrate, and fire regime. Pine rocklands in the lower Keys often have high amounts of
Thrinax and
Coccothrinax, while rocklands in Miami-Dade County have high amounts of
Sabal palmetto,
Ficus aurea, and
Serenoa repens. Sites that share borders with hardwood hammocks or that are infrequently burned will have high amounts of hardwood species, including
Metopium toxiferum,
Quercus elliotti,
Quercus virginiana,
Sideroxylon salicifolium, and
Lysiloma latisiliquum. The shrub layer near wet prairies and marshes is composed of wetland species such as
Acacia pinetorum,
Sambucus canadensis, and
Taxodium ascendens. The herbaceous layer is extremely diverse and home to several species considered rare, endangered, threatened or critically imperiled by one or more agencies. In fact, the Florida landscape is estimated to have been dominated by dry season lightning-induced and human-ignited fires. Most of the native plant species found in pine rocklands are adapted to periodic fires, with increased abundance and flowering of native plants found in plots post-burn. These fires help curb hardwood encroachment, spur pine regeneration, and allow light to reach the herbaceous layer. In the absence of fire, hardwood species from nearby hardwood hammocks invade and shade out natural vegetation. As the density of hardwood species increases, fire effectiveness decreases due to the increase in humidity and accumulation of poor fire fuels. This ecotone between pine rockland and hardwood hammock is clear when natural or frequent, low-intensity prescribed fires occur. In the absence of frequent fire, this distinction becomes less apparent. Presently, many isolated pine rockland sites throughout Miami-Dade County and the lower Keys suffer from fire suppression, leading to drastically altered plant compositions. It is estimated that around 5,000,000 ha of pine rocklands burned in 1926, whereas only 76,486 ha burned in 1995 and 2003. Most sites located in Miami-Dade County and the lower Keys are located near residential or commercial lots and are often unable to implement prescribed burns. The longer fire is suppressed, the harder and more dangerous it is to prescribe effective burns. Fuel loads increase between fires and result in hotter and higher flames. Fires that are too high or intense can result in crown fire or mortality at all levels of the canopy, including below ground biomass. Frequent fire is used to great effect in the Long Pine Key in Everglades National Park. ==Rockland hammock==