Physiognomy and Structure: The slash pine forest in this macrogroup is characterized by an open canopy, generally with multiple age classes, of the needle-leaved evergreen conifer Pinus elliottii var. densa, associated with a high diversity of palms, hardwoods and herbaceous plants in the understory, most derived from the tropical flora of the West Indies (Snyder et al. 1990). Many of these species vary in height depending on fire frequency, getting taller with time since fire (FNAI 2010a).

Floristics: Pinus elliottii var. densa is the characteristic and often dominant pine species of the macrogroup distribution in the continental United States. Characteristic pine species in the communities further south and in the Caribbean include Pinus caribaea (var. bahamensis, var. caribaea, and var. hondurensis), and Pinus tropicalis. It has been estimated that nearly one-third of the taxa found in the south Florida pine rockland are restricted to it, including half of southern Florida''s endemic plants (Stout and Marion 1993). Shrubs include Chrysobalanus icaco, Coccothrinax argentata, Ilex cassine, Sideroxylon salicifolium, Tetrazygia bicolor, and Leucothrinax morrisii (= Thrinax morrisii). More common and representative (if not diagnostic) species on the mainland and Florida Keys include Byrsonima lucida, Dodonaea viscosa, Guettarda elliptica, Guettarda scabra, and Serenoa repens. Similar open pine forests occur in the northern Bahama Archipelago and along the coast in western and eastern Cuba where they are known as pine barrens or pine woodlands and are dominated by Pinus caribaea, Pinus tropicalis, and Pinus cubensis, respectively, accompanied by a similar set of species such as the palms Coccothrinax argentata, Coccothrinax miraguana, Coccothrinax orientalis, Coccothrinax yuraguana, and Leucothrinax morrisii. Other species include Byrsonima lucida, Dodonaea viscosa, Guettarda elliptica, Guettarda scabra, Rhus copallinum, Serenoa repens, Tabebuia bahamensis, Tabebuia dubia, Tabebuia lepidophylla, Tabebuia shaferi, and Zamia pumila (T. Armentano pers. comm. 2003). The macrogroup also includes pine-oak dry forests in western Cuba, where the oak species Quercus oleoides also occurs in the Dry Evergreen Oak forest type distributed in Mesoamerica and included in the macrogroup.

Dynamics:  Pine rockland is maintained by regular fire (O''Brien et al. 2008), and susceptible to other natural disturbances such as hurricanes, frost events, and sea-level rise (Ross et al. 1994, as cited in FNAI 2010a). Fires historically burned on an interval of around 3 to 7 years (Snyder et al. 1990) and were typically started by lightning strikes during the frequent summer thunderstorms. Presently, prescribed fire must be periodically introduced into pine rocklands to sustain community structure, prevent invasion by woody species, maintain high herbaceous diversity (Loope and Dunevitz 1981, as cited in FNAI 2010a), and prevent succession to rockland hammock. The ecotone between pine rockland and rockland hammock in Florida is abrupt when regular fire is present in the system. In the absence of fire, the pine rockland may be replaced by hardwood species within several decades (Stout and Marion 1993). Fire is also reported as part of the natural dynamic of dry, pre-montane, mixed Pinus caribaea - Quercus oleoides forests of Belize and Honduras, another community represented within this macrogroup. See also Kennedy and Horn (2008).

Hurricanes and storms can have a major impact on pine rocklands. High winds can significantly affect plant structure or composition by causing canopy and subcanopy mortality (Platt et al. 2000, as cited in FNAI 2010a), resulting in subsequent stimulation of shrub or herbaceous growth. Pine rocklands near the coast may be temporarily inundated by saltwater during severe storms, which can kill or damage vegetation (Snyder et al. 1990). Rare frost events bringing below-freezing temperatures can reduce tropical hardwoods. Because tropical and subtropical plants in pine rocklands are more exposed to below-freezing temperatures in the relatively open understory, they are more likely to succumb to freeze damage than their counterparts in sheltered rockland hammocks (FNAI 2010a). The area of pine rockland in the Florida Keys has been reduced since the 1930s. This is at least partially due to increased ground and soil salinity resulting from a 15-cm local rise in sea level that has occurred since that time (Ross et al. 1994, as cited in FNAI 2010a).

The fire cycle is central to succession in these pine forest communities in the Caribbean, and palms, shrubs and hardwood trees are dynamic structural components. That is, they are relatively sensitive to fires not intense enough to cause the complete replacement of the stand, but recover quickly thereafter. This is surely true for shrubs and hardwoods, which resprout prolifically after fire, but palms grow very slowly and do not resprout. Besides intensity, season of fire is also an important component in the fire regime of pine forests in the Caribbean, as it may influence fuel consumption, fire intensity, and forest development during the post-burn period (Liu and Menges 2005 and references therein). In addition to its effects on existing vegetation, a very intense fire may hinder recovery of the plant community (Spier and Snyder 1998), thereby constraining the development of fuel loads in the post-burn period. Thus the effect of different fire cycles, natural or human-caused, has the capacity to result in different structure and composition of the pine forest ecosystems. In addition to fires, hurricanes are another major natural disturbance affecting the distribution, composition and structure of the pine forests.