patrickbdevaney/mia9 · Datasets at Hugging Face

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endemic species. At present, the most common herbs in Miami-Dade County pine rocklands, in
descending order, are pine fern, low rattlebox, Florida five-petalled leafflower, rhizomatous
bluestem, coastal bedstraw, three-seeded mercury, crimson bluestem, pitted stripeseed, Florida
whitetop, and wire bluestem (Bradley, unpublished data). The composition and relative
abundance of herbs in MDC pine rocklands may have differed historically from present
populations.
Composition of the herb layer varies greatly with geographic location, soils, and hydrology. Like
the subcanopy, more temperate species are to the north and tropical species to the south. The
herb layer in sandy areas of the northern Biscayne pinelands may resemble central Florida
sandhill ecosystems. Low elevation areas that flooded seasonally consist of plant species that are
common in marl prairies, such as rhizomatous bluestem, muhlygrass, sawgrass, and starrush
whitetop.
The diversity and density of the herb layer is reduced in areas of heavy hardwood density, such
as near rockland hammocks. Hardwoods limit the herb layer by limiting sunlight penetration to
the ground and by producing a layer of leaf litter that can smother small herbs and limit their
germination.
2.5 Association with Other Habitat Types
Prior to non-indigenous settlement of Miami-Dade County, pine rockland habitat was the
dominant plant community on the Miami Rock Ridge. Pine rocklands merged into other habitats,
and under proper circumstances succeeded to or from these other habitats. Ecotones between
pine rockland and other habitats were historically important habitat for many plant and animal
species.
Rockland hammocks historically occurred across the range of pine rocklands in Miami-Dade
County. Rockland hammocks are closed canopy hardwood forests usually dominated by tropical
tree species and the temperate live oak. Rockland hammocks covered small areas of a few acres
up to several hundred acres. They occurred in areas that were protected from the fires that burned
pine rocklands, typically on the edges of wetlands or in association with abundant solution holes
in the oolitic limestone. Pine rockland can succeed into rockland hammock in the absence of fire,
and rockland hammocks can succeed into pine rockland with frequent fires. Many plant species
grow primarily at the ecotone between pine rockland and rockland hammock, including several
that are now rare or imperiled. The ecotone was also very important for wildlife, which used both
ecosystems. The rockland hammock ecosystem is discussed as an independent chapter in this
management plan.
Alexander (1967) reported results of a 25-year study on pine rockland to rockland hammock
succession. He reports:
“…a complete change from pineland fire-climax to a well-established climatic climax of
West Indian tropical flora with Lysiloma bahamensis acting as the invader tree can occur
in 25 years in southern Florida.”
This statement that pine rocklands can succeed to rockland hammocks within two (2) to three (3)
decades of fire suppression has been mistakenly inferred by many readers. While pine rocklands
EEL Program, Management Plan, Part II – Pine Rockland (DRAFT) _____________________________________________________________________________________________________________________
Page 9
are fire climax communities, that is, pinelands thrive in an ecosystem subjected to a natural
frequency of fires, Alexander’s statement may not be applicable to all pine rocklands in MiamiDade County. Alexander’s results, while accurate for his study, cannot be extrapolated to most
pine rockland fragments since his study site was right between two hammocks. Most pine
rockland sites in the County occur far away from hammocks.
Alexander’s study area, established by Phillips (1940) 25 years previously, was situated between
Castellow and Ross Hammocks, which were only separated by about 500 feet. This 500 foot gap
was filled with a narrow strip of pine rockland. Succession between the Phillips and Alexander
studies was undoubtedly rapid due to heavy seed rain from the adjacent hammocks. Hardwood
stem densities, (e.g. false tamarind) may have been high at the study site even before fire
suppression. Stem densities are typically higher adjacent to rocklands because of heavy seed
rain, but frequent fires keep overall biomass low.
Long-term fire suppression in other pine rockland sites has resulted in conditions similar to
Alexander’s at only a few sites – all adjacent to rockland hammocks. The Camp Owaissa Bauer
Addition EEL site serves as an example. Even in this situation, the succeeded flora consists of a
low diversity of trees, shrubs, and herbs and does not approach the biological diversity of mature
rockland hammocks. This can be observed in the vicinity of Alexander’s study. The area is
dominated by wild tamarind and several other hardwoods, but vegetation structure and
composition is clearly distinct form the interiors of the adjacent hammocks.
More typically, pine rocklands that have been fire suppressed and are not close to rockland
hammocks develop into dense shrublands. Height and coverage of understory palms, especially
saw palmetto and cabbage palm, increases as do understory hardwoods such as wax myrtle,
myrsine, and marlberry. Most fire suppressed sites also have dense coverage of exotic pest
plants, especially Brazilian pepper and Burma reed. As a general rule, pine rocklands do not
succeed to rockland hammocks without the proper seed sources, and even then the time to reach
complete succession to a climax rockland hammock is unknown.
Marl prairies dissected the Miami Rock Ridge, dividing the pine rocklands into a series of
isolated islands. Marl prairies are short hydroperiod wetlands with a marl soil substrate that is
derived from the precipitation of calcium carbonate from periphyton. The marl prairies that were
adjacent to pine rocklands were mainly treeless, dominated by forbs, grasses, and sedges. Water
stood or flowed through these prairies for up to several months during the summer wet season.
Where pine rockland and marl prairie intersected there was a mix of plant species common to
both communities. It is likely that wildlife use was heavy, especially for terrestrial animals that
visited the edges of the marl prairies for drinking water. The marl prairie ecosystem is discussed
as an independent chapter in this management plan.
2.6 Historical Successional Processes
The pine rockland ecosystem is subject to a number of natural stressors, which influence
community structure and composition. In some circumstances the pine rockland community can
succeed into other ecosystems. Natural processes that determine the ecological characteristics of
pine rocklands include fires, the regular occurrence of tropical cyclones, and the rather sporadic
incidence of frosts.
EEL Program, Management Plan, Part II – Pine Rockland (DRAFT) _____________________________________________________________________________________________________________________
Page 10
2.6.1 Fire
Fire frequency for pine rocklands in
Miami-Dade County is generally accepted
as about once every three (3) to seven (7)
years (Hofstetter 1973, Snyder 1990,
USFWS 2000), although Olmsted and
Loope (1984) suggest that 3-7 years may
be too frequent for young pines to attain a
large enough size to survive a fire. It has
been suggested that these fires are usually
ignited by lightning in the summer rainy
season between June and October (Doren
et al. 1993), or between April and June
(Beckage et al. 2003). Given that lightning
strikes occur year-round, and begin to
increase in the transition from the dry season to the wet season between March and May

endemic species. At present, the most common herbs in Miami-Dade County pine rocklands, in

descending order, are pine fern, low rattlebox, Florida five-petalled leafflower, rhizomatous

bluestem, coastal bedstraw, three-seeded mercury, crimson bluestem, pitted stripeseed, Florida

whitetop, and wire bluestem (Bradley, unpublished data). The composition and relative

abundance of herbs in MDC pine rocklands may have differed historically from present

populations.

Composition of the herb layer varies greatly with geographic location, soils, and hydrology. Like

the subcanopy, more temperate species are to the north and tropical species to the south. The

herb layer in sandy areas of the northern Biscayne pinelands may resemble central Florida

sandhill ecosystems. Low elevation areas that flooded seasonally consist of plant species that are

common in marl prairies, such as rhizomatous bluestem, muhlygrass, sawgrass, and starrush

whitetop.

The diversity and density of the herb layer is reduced in areas of heavy hardwood density, such

as near rockland hammocks. Hardwoods limit the herb layer by limiting sunlight penetration to

the ground and by producing a layer of leaf litter that can smother small herbs and limit their

germination.

2.5 Association with Other Habitat Types

Prior to non-indigenous settlement of Miami-Dade County, pine rockland habitat was the

dominant plant community on the Miami Rock Ridge. Pine rocklands merged into other habitats,

and under proper circumstances succeeded to or from these other habitats. Ecotones between

pine rockland and other habitats were historically important habitat for many plant and animal

species.

Rockland hammocks historically occurred across the range of pine rocklands in Miami-Dade

County. Rockland hammocks are closed canopy hardwood forests usually dominated by tropical

tree species and the temperate live oak. Rockland hammocks covered small areas of a few acres

up to several hundred acres. They occurred in areas that were protected from the fires that burned

pine rocklands, typically on the edges of wetlands or in association with abundant solution holes

in the oolitic limestone. Pine rockland can succeed into rockland hammock in the absence of fire,

and rockland hammocks can succeed into pine rockland with frequent fires. Many plant species

grow primarily at the ecotone between pine rockland and rockland hammock, including several

that are now rare or imperiled. The ecotone was also very important for wildlife, which used both

ecosystems. The rockland hammock ecosystem is discussed as an independent chapter in this

management plan.

Alexander (1967) reported results of a 25-year study on pine rockland to rockland hammock

succession. He reports:

“…a complete change from pineland fire-climax to a well-established climatic climax of

West Indian tropical flora with Lysiloma bahamensis acting as the invader tree can occur

in 25 years in southern Florida.”

This statement that pine rocklands can succeed to rockland hammocks within two (2) to three (3)

decades of fire suppression has been mistakenly inferred by many readers. While pine rocklands

EEL Program, Management Plan, Part II – Pine Rockland (DRAFT) _____________________________________________________________________________________________________________________

Page 9

are fire climax communities, that is, pinelands thrive in an ecosystem subjected to a natural

frequency of fires, Alexander’s statement may not be applicable to all pine rocklands in MiamiDade County. Alexander’s results, while accurate for his study, cannot be extrapolated to most

pine rockland fragments since his study site was right between two hammocks. Most pine

rockland sites in the County occur far away from hammocks.

Alexander’s study area, established by Phillips (1940) 25 years previously, was situated between

Castellow and Ross Hammocks, which were only separated by about 500 feet. This 500 foot gap

was filled with a narrow strip of pine rockland. Succession between the Phillips and Alexander

studies was undoubtedly rapid due to heavy seed rain from the adjacent hammocks. Hardwood

stem densities, (e.g. false tamarind) may have been high at the study site even before fire

suppression. Stem densities are typically higher adjacent to rocklands because of heavy seed

rain, but frequent fires keep overall biomass low.

Long-term fire suppression in other pine rockland sites has resulted in conditions similar to

Alexander’s at only a few sites – all adjacent to rockland hammocks. The Camp Owaissa Bauer

Addition EEL site serves as an example. Even in this situation, the succeeded flora consists of a

low diversity of trees, shrubs, and herbs and does not approach the biological diversity of mature

rockland hammocks. This can be observed in the vicinity of Alexander’s study. The area is

dominated by wild tamarind and several other hardwoods, but vegetation structure and

composition is clearly distinct form the interiors of the adjacent hammocks.

More typically, pine rocklands that have been fire suppressed and are not close to rockland

hammocks develop into dense shrublands. Height and coverage of understory palms, especially

saw palmetto and cabbage palm, increases as do understory hardwoods such as wax myrtle,

myrsine, and marlberry. Most fire suppressed sites also have dense coverage of exotic pest

plants, especially Brazilian pepper and Burma reed. As a general rule, pine rocklands do not

succeed to rockland hammocks without the proper seed sources, and even then the time to reach

complete succession to a climax rockland hammock is unknown.

Marl prairies dissected the Miami Rock Ridge, dividing the pine rocklands into a series of

isolated islands. Marl prairies are short hydroperiod wetlands with a marl soil substrate that is

derived from the precipitation of calcium carbonate from periphyton. The marl prairies that were

adjacent to pine rocklands were mainly treeless, dominated by forbs, grasses, and sedges. Water

stood or flowed through these prairies for up to several months during the summer wet season.

Where pine rockland and marl prairie intersected there was a mix of plant species common to

both communities. It is likely that wildlife use was heavy, especially for terrestrial animals that

visited the edges of the marl prairies for drinking water. The marl prairie ecosystem is discussed

as an independent chapter in this management plan.

2.6 Historical Successional Processes

The pine rockland ecosystem is subject to a number of natural stressors, which influence

community structure and composition. In some circumstances the pine rockland community can

succeed into other ecosystems. Natural processes that determine the ecological characteristics of

pine rocklands include fires, the regular occurrence of tropical cyclones, and the rather sporadic

incidence of frosts.

EEL Program, Management Plan, Part II – Pine Rockland (DRAFT) _____________________________________________________________________________________________________________________

Page 10

2.6.1 Fire

Fire frequency for pine rocklands in

Miami-Dade County is generally accepted

as about once every three (3) to seven (7)

years (Hofstetter 1973, Snyder 1990,

USFWS 2000), although Olmsted and

Loope (1984) suggest that 3-7 years may

be too frequent for young pines to attain a

large enough size to survive a fire. It has

been suggested that these fires are usually

ignited by lightning in the summer rainy

season between June and October (Doren

et al. 1993), or between April and June

(Beckage et al. 2003). Given that lightning

strikes occur year-round, and begin to

increase in the transition from the dry season to the wet season between March and May