South Florida Hardwood Hammock
Summary
This rockland tropical hammock system, as currently defined, occurs only in extreme southern Florida. It consists of upland hardwood forest on elevated ridges of limestone in three discrete major regions; the Keys, southeastern Big Cypress, and the Miami Rock Ridge. Tropical hardwood species are diagnostic of the system. Among the species likely to be encountered throughout are Bursera simaruba, Coccoloba diversifolia, and Eugenia axillaris. Quercus laurifolia is one of the few temperate species which attains prominence in this system. These forests tend to have a dense canopy that produces deeper shade, less evaporation, and lower air temperature than surrounding vegetation. This microclimate, in combination with high water tables, tends to keep humidity levels high. A number of orchid and bromeliad species thrive in such conditions. Unlike most coastal plain systems, fire is a major threat to South Florida Hardwood Hammock (CES411.287). For this reason, many examples occur alongside natural firebreaks.
Source: NatureServe Explorer
Vegetation
There tends not to be strong dominance in these forests, so the principal species list can be long. Tropical hardwood species are diagnostic of the system, although few are common or dominant in all regions where these hammocks occur (Snyder et al. 1990). Among the species likely to be encountered throughout are Bursera simaruba, Coccoloba diversifolia, and Eugenia axillaris. The northward ranges of these species are limited by the incidence of frosts (Drew and Schomer 1984). Other typical dominant tree species, in no real order, are Metopium toxiferum, Swietenia mahagoni, Zanthoxylum fagara, Gymnanthes lucida (= Ateramnus lucidus), Piscidia piscipula, and Pithecellobium keyense (T. Armentano pers. comm.). Other species can include Lysiloma latisiliquum, Nectandra coriacea, Ficus aurea, Sideroxylon foetidissimum, Eugenia foetida, Guapira discolor, Coccoloba uvifera, Leucothrinax morrisii (= Thrinax morrisii), Thrinax radiata, Erithalis fruticosa, Krugiodendron ferreum, Casasia clusiifolia, Erithalis fruticosa, Byrsonima lucida, and Capparis flexuosa.
Source: NatureServe Explorer
Environment
This system occurs in three discrete regions of south Florida. Underlying geology and soils are somewhat different among these regions, and the juxtaposition of the system may be somewhat unique. Generally, soils are highly organic with uneven and widely ranging thickness (Snyder et al. 1990). These forests tend to have a dense canopy that produces deeper shade, less evaporation, and lower air temperature than surrounding vegetation. This microclimate, in combination with high water tables, tends to keep humidity levels high and the community quite mesic (FNAI 1990). Unlike most coastal plain ecological systems, fire is a major threat to South Florida Hardwood Hammock (CES411.287). For this reason, many examples occur alongside natural firebreaks, such as the leeward side of exposed limestone (Robertson 1955), moats created by limestone solution (Duever et al. 1986), and elevated outcrops above marshes, scrub cypress, or sometimes mangrove swamps (Snyder et al. 1990).
Source: NatureServe Explorer
Dynamics
Groundwater and seasonal pooling and drying of the soil are important dynamics. There is organic soil accumulation, thick in some areas and thin in others. Solution-eroded limestone provides wet pockets and dry patches in the environment. Thick organic soil helps maintain high levels of moisture in the system. Hurricanes are a part of the natural dynamics of this ecological system. Fire is very infrequent, due to the protection of this ecological system, many examples occur alongside natural firebreaks.
Source: NatureServe Explorer
Threats
Unlike most coastal plain systems, fire is a major threat to South Florida Hardwood Hammock (CES411.287). Deep duff burning will kill >75% of the upper canopy layer, due to root and cambial damage (Landfire 2007a). Lowered water tables contribute to drying out of the litter and duff, which can allow wildfires to burn much more severely (Enge et al. 2002). The drainage and extensive severe wildfires early in the 20th century led to the loss of much of this habitat. Much of the remaining habitat has now been developed (Enge et al. 2002). Commercial and residential development are threats. Invasive exotic species are a threat, both plants and animals. There are many exotic tropical plants and animals which have naturalized in south Florida. Species such as Colubrina asiatica, Leucaena leucocephala, Manilkara zapota, Schinus terebinthifolius, and Thespesia populnea invade and displace native species. Dumping of yard waste can lead to the invasion of species such as Sansevieria hyacinthoides and Epipremnum pinnatum (FNAI 2010a).
Source: NatureServe Explorer
Distribution
This system is endemic to south Florida.
Source: NatureServe Explorer
Ecologically Associated Plant Species
Plant species that characterize this ecosystem type, organized by vegetation stratum. These are species ecologically associated with the ecosystem, not confirmed present in any specific area.
Tree canopy
Bursera simaruba, Coccoloba diversifolia, Coccoloba uvifera, Lysiloma latisiliquum, Metopium toxiferum, Piscidia piscipula, Pithecellobium keyense, Quercus laurifolia, Sideroxylon foetidissimum, Swietenia mahagoni, Thrinax radiata
Shrub/sapling (tall & short)
Byrsonima lucida, Casasia clusiifolia, Erithalis fruticosa, Eugenia axillaris, Eugenia foetida, Guapira discolor, Gymnanthes lucida, Krugiodendron ferreum, Nectandra coriacea, Thrinax morrisii, Zanthoxylum fagara
Herb (field)
Cynophalla flexuosa, Ficus aurea
Nonvascular
Acroporium smallii, Plagiochila micropteryx
Source: NatureServe Ecological System assessment
Ecologically Associated Animals (2)
Animal species ecologically associated with this ecosystem type based on NatureServe assessment. These are species whose habitat requirements overlap with this ecosystem, not confirmed present in any specific roadless area.
Source: NatureServe Ecological System assessment
At-Risk Species Associated with this Ecosystem (3)
Species with conservation concern that are ecologically associated with this ecosystem type. G-Rank indicates global conservation status: G1 (critically imperiled) through G5 (secure). ESA status indicates U.S. Endangered Species Act listing.
Source: NatureServe Ecological System assessment
Component Associations (14)
Plant community associations that occur within this ecological system. Associations are the finest level of the U.S. National Vegetation Classification (USNVC) and describe specific, repeating assemblages of plant species. Each association represents a distinct community type that may be found where this ecosystem occurs.
| Name | G-Rank | |
|---|
| Bursera simaruba - Swietenia mahagoni - Lysiloma latisiliquum / Nectandra coriacea - Coccoloba diversifolia Forest | G1 | NatureServe |
| Casasia clusiifolia - Guapira discolor - Pithecellobium keyense - Metopium toxiferum Forest | G1 | NatureServe |
| Conocarpus erectus - Sideroxylon celastrinum - Erithalis fruticosa - Manilkara jaimiqui ssp. emarginata Forest | G1 | NatureServe |
| Ficus aurea - Sideroxylon foetidissimum - Bursera simaruba / Eugenia foetida - Guapira discolor Forest | G1 | NatureServe |
| Magnolia virginiana - (Sabal palmetto) Tropical Shell Midden Woodland | G2 | NatureServe |
| Metopium toxiferum - Eugenia foetida - Coccoloba uvifera - Leucothrinax morrisii / Erithalis fruticosa Forest | G2 | NatureServe |
| Metopium toxiferum - Eugenia foetida - Krugiodendron ferreum - Swietenia mahagoni / Capparis flexuosa Forest | G2 | NatureServe |
| Metopium toxiferum - Leucothrinax morrisii - Byrsonima lucida / Schizachyrium spp. Woodland | G1 | NatureServe |
| Morella cerifera - Ilex cassine - Quercus virginiana - Serenoa repens Scrub | G2 | NatureServe |
| Opuntia stricta - Acanthocereus tetragonus - Evolvulus convolvuloides - Indigofera oxycarpa Shrubland | G1 | NatureServe |
| Pteridium caudatum Forb Vegetation | GNR | NatureServe |
| Sideroxylon foetidissimum - Sideroxylon salicifolium - Ficus aurea - Quercus virginiana - Celtis laevigata Forest | G1 | NatureServe |
| Strumpfia maritima Shrubland | G1 | NatureServe |
| Thrinax radiata - Casasia clusiifolia - Erithalis fruticosa Forest | G1 | NatureServe |
State Conservation Ranks (1)
Subnational conservation status ranks (S-ranks) assigned by Natural Heritage Programs in each state where this ecosystem occurs. S1 indicates critically imperiled at the state level, S2 imperiled, S3 vulnerable, S4 apparently secure, and S5 secure. An ecosystem may be globally secure but imperiled in specific states at the edge of its range.
Methodology and Data Sources
Ecosystem classification: Ecosystems are classified using the LANDFIRE 2024 Existing Vegetation Type (EVT) layer, mapped to NatureServe Terrestrial Ecological Systems via a curated crosswalk. Each EVT is linked to the USNVC (U.S. National Vegetation Classification) hierarchy through pixel-level co-occurrence analysis of LANDFIRE EVT and NatureServe IVC Group rasters across all roadless areas.
Vegetation coverage: Coverage percentages and hectares are derived from zonal statistics of the LANDFIRE 2024 EVT raster intersected with roadless area boundaries.
Ecosystem narratives and community species: Sourced from the NatureServe Explorer API, representing professional ecological assessments of vegetation composition, environmental setting, dynamics, threats, and characteristic species assemblages.
IVC hierarchy: The International Vegetation Classification hierarchy is sourced from the USNVC v3.0 Catalog, providing the full classification from Biome through Association levels.
Component associations: Plant community associations listed as components of each NatureServe Ecological System. Association data from the NatureServe Explorer API.
State ranks: Conservation status ranks assigned by NatureServe member programs in each state where the ecosystem occurs.