patrickbdevaney/mia9 · Datasets at Hugging Face

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soil is slightly basic (Craighead 1971, USFWS 2000) and dark reddish to brown in color
(typically called “Redland Soil”) (USDA 1996). It was from the color of this soil that the
“Redlands” area of southern Miami-Dade County derived its name. Cardsound soil is usually
only about four (4) inches thick and soil permeability is moderately slow (USDA 1996). Unlike
Opalocka soil, there is very little visible Cardsound soil in pine rocklands. The existing deposits
usually cover very small areas of a few square meters or less.
Pine rocklands are also known to contain features called solution holes. Solution holes are
“steep-sided pits of varying sizes formed by the dissolution of rock below the surface followed
by collapse at the top” (Myers and Ewel 1990). Deeper deposits of typically organic soil, noncharacteristic of the typical nutrient-poor sand or loam found in pine rocklands, may be found
within these holes.
2.2.3 Hydrology
Pre-drainage hydrology of pine rocklands varied greatly depending upon elevation. Some pine
rocklands, especially those further north in the county, probably never flooded, or flooded for
only very brief periods during major high water events. Other pine rocklands, such as those
along the west edge of the western Miami Rock Ridge or along the edges of the Transverse
Glades, probably flooded annually for short periods during the summer wet season. Pine
EEL Program, Management Plan, Part II – Pine Rockland (DRAFT) _____________________________________________________________________________________________________________________
Page 6
rocklands on Long Pine Key in ENP may flood for 20 to 60 days per year (Duever et al. 1979),
because these are at lower elevations than most pine rocklands outside of ENP.
2.3 Climate
Miami-Dade County has a subtropical climate that can be divided into two distinct seasons: a
mild dry season and a hot rainy season. The dry season is characterized by mild temperatures,
relatively low humidity, and very little rain. This season usually ranges from late October to mid
May. Occasional cold fronts arriving from Canada are the primary force of weather during the
dry season, disrupting a mild easterly flow off the Atlantic Ocean. High temperatures are
generally around 80 degrees and low temperatures can vary from the low 30s inland to the low
60s near the coast. Temperatures below 32 degrees occur some years. Humidity levels are
generally low with dew points below 60 degrees. The start of the wet season is different every
year, but it generally starts in mid May and lasts through October. The average temperatures
during the wet season range from the upper 80s along the coast to the mid 90s inland.
Precipitation amounts can be copious with monthly totals ranging from five (5) to nine (9) inches
and an annual average of 58 inches. The distinct mark of the wet season is consecutive days of
high humidity with dew points at or well above 60 degrees.
June 1 through November 30 marks the annual hurricane season. During this period Miami-Dade
County may be crossed by one or more tropical cyclones, including tropical depressions, tropical
storms, and hurricanes. The main impact of these storms is the strong winds. Hurricanes have
winds in excess of 74 miles per hour and can bring large amounts of rainfall in very short time
periods, causing regional flooding.
2.4 Vegetation Structure and Composition
Typically pine rocklands consist of three vegetation layers that vary in importance and diversity
according to specific local conditions. A canopy normally dominated by pine trees is followed by
a subcanopy composed of an array of temperate and tropical hardwoods and palms and a diverse
herb layer of a combination of forbs, grasses, ferns, and sedges. Details of the structure and
species richness of each of these layers is provided in the following paragraphs. Please refer to
Appendix B for pictures of historical vegetation structure and composition.
2.4.1 Canopy
The canopy of pine rocklands is dominated by a single species, South Florida slash pine, which
historically ranged in height from approximately 65 to 90 feet (Craighead 1971, Snyder et al.
1990). Diameters of pines historically ranged up to 24 to 30 inches (Craighead 1971, Robertson
1955). Platt et al. (2002) reported pre-Hurricane Andrew pine densities on fragmented pine
rockland sites of between 211 and 975 trees per acre. In the Long Pine Key area of ENP, preHurricane Andrew slash pine densities were recorded at 185 to 477 trees per acre (Snyder et al.
1990) and 294 to 863 trees per acre (Platt et al. 2002). Germination of South Florida slash pine
occurs from October to December. Seedling survival is higher where there is more soil moisture
(McMinn 1970). Seedlings will remain in a fire resistant “grass stage” for two (2) to five (5)
years. While in this grass stage the pines can re-sprout from the root collar after a fire (Ketcham
and Bethune 1963), allowing some to survive. Hofstetter (1973) reported that fires cause an 87%
EEL Program, Management Plan, Part II – Pine Rockland (DRAFT) _____________________________________________________________________________________________________________________
Page 7
mortality of seedlings less than five (5) feet tall and 50% mortality for those 6.6 to 19.8 feet tall.
Seedlings have improved survivability in areas with less duff accumulation (Klukas 1973).
2.4.2 Subcanopy
The subcanopy of pine rocklands consists of a diverse mix of temperate and tropical hardwoods
and palms. Almost 100 native plant species may be present in the subcanopy of Miami-Dade’s
pine rocklands (Bradley, unpublished data). Palms in this layer, all fairly common, include saw
palmetto, cabbage palm, and silver palm, with saw palmetto being the most common and
typically a dominant species in all pine rockland areas. Where pine rocklands historically
experienced seasonal flooding, or had a shallow depth to the water table, cabbage palm becomes
a more dominant species.
Common hardwoods in pine rocklands presently include live oak, poisonwood, southern sumac,
white indigo berry, myrsine, West Indian-lilac, snowberry, nettletree, rough velvetseed, and
willow bustic (Bradley, unpublished data). The ratio of temperate species to tropical species
declines from north to south, with many temperate species becoming absent towards the southern
end of the Miami Rock Ridge, and many tropical species becoming absent to the north. The
subcanopy in the north may resemble a central Florida sandhill more than a pine rockland further
south on the ridge. Historical composition and relative abundance of understory hardwoods may
have differed from current coverage.
In addition to the above hardwoods there are many small shrubs or sub-woody species that can
be conspicuous components of pine rocklands. These include lacy bracken fern, dwarf live oak,
pineland croton, pineland snowberry, partridge pea, and wild sage.
Subcanopy height and density varies temporally and spatially depending on time since fire,
freezes, and distance to rockland hammock communities. Fires, discussed in more detail in
Section 2.6.1 below, historically occur naturally every three (3) to seven (7) years and kill or topkill hardwoods. Freezes and cold weather kill or top-kill more sensitive tropical hardwoods such
as poisonwood and West Indian-lilac (Olmsted et al. 1993). Diversity and stem density of
hardwoods is usually higher in close proximity to rockland hammocks, which serve as a source
for seed rain into the pine rocklands.
No historical data are known that quantified the original density of palms and hardwoods in pine
rockland prior to non-indigenous settlement. Photos from the early 1900s show areas with a very
low palm/shrub layer (less than two feet), but it is difficult to know how representative these
photos are of pine rocklands as a whole (Appendix B). Pine rocklands probably had a subcanopy
layer mostly less than two (2) feet tall. Overall cover of palms and shrubs was probably less thas
25%, with a great degree of patchiness resulting in some very open areas and some very dense
areas.
2.4.3 Herb Layer
Over 225 species of herbs may be found in the pine rocklands of Miami-Dade County (Bradley,
unpublished data). The herb layer consists of forbs, grasses, ferns, and sedges. This herb layer is
much more diverse and has a greater cover where the subcanopy layer is sparse. This herb layer,
much like the subcanopy, consists of temperate and tropical species, but also has a component of
EEL Program, Management Plan, Part II – Pine Rockland (DRAFT) _____________________________________________________________________________________________________________________
Page 8

soil is slightly basic (Craighead 1971, USFWS 2000) and dark reddish to brown in color

(typically called “Redland Soil”) (USDA 1996). It was from the color of this soil that the

“Redlands” area of southern Miami-Dade County derived its name. Cardsound soil is usually

only about four (4) inches thick and soil permeability is moderately slow (USDA 1996). Unlike

Opalocka soil, there is very little visible Cardsound soil in pine rocklands. The existing deposits

usually cover very small areas of a few square meters or less.

Pine rocklands are also known to contain features called solution holes. Solution holes are

“steep-sided pits of varying sizes formed by the dissolution of rock below the surface followed

by collapse at the top” (Myers and Ewel 1990). Deeper deposits of typically organic soil, noncharacteristic of the typical nutrient-poor sand or loam found in pine rocklands, may be found

within these holes.

2.2.3 Hydrology

Pre-drainage hydrology of pine rocklands varied greatly depending upon elevation. Some pine

rocklands, especially those further north in the county, probably never flooded, or flooded for

only very brief periods during major high water events. Other pine rocklands, such as those

along the west edge of the western Miami Rock Ridge or along the edges of the Transverse

Glades, probably flooded annually for short periods during the summer wet season. Pine

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

Page 6

rocklands on Long Pine Key in ENP may flood for 20 to 60 days per year (Duever et al. 1979),

because these are at lower elevations than most pine rocklands outside of ENP.

2.3 Climate

Miami-Dade County has a subtropical climate that can be divided into two distinct seasons: a

mild dry season and a hot rainy season. The dry season is characterized by mild temperatures,

relatively low humidity, and very little rain. This season usually ranges from late October to mid

May. Occasional cold fronts arriving from Canada are the primary force of weather during the

dry season, disrupting a mild easterly flow off the Atlantic Ocean. High temperatures are

generally around 80 degrees and low temperatures can vary from the low 30s inland to the low

60s near the coast. Temperatures below 32 degrees occur some years. Humidity levels are

generally low with dew points below 60 degrees. The start of the wet season is different every

year, but it generally starts in mid May and lasts through October. The average temperatures

during the wet season range from the upper 80s along the coast to the mid 90s inland.

Precipitation amounts can be copious with monthly totals ranging from five (5) to nine (9) inches

and an annual average of 58 inches. The distinct mark of the wet season is consecutive days of

high humidity with dew points at or well above 60 degrees.

June 1 through November 30 marks the annual hurricane season. During this period Miami-Dade

County may be crossed by one or more tropical cyclones, including tropical depressions, tropical

storms, and hurricanes. The main impact of these storms is the strong winds. Hurricanes have

winds in excess of 74 miles per hour and can bring large amounts of rainfall in very short time

periods, causing regional flooding.

2.4 Vegetation Structure and Composition

Typically pine rocklands consist of three vegetation layers that vary in importance and diversity

according to specific local conditions. A canopy normally dominated by pine trees is followed by

a subcanopy composed of an array of temperate and tropical hardwoods and palms and a diverse

herb layer of a combination of forbs, grasses, ferns, and sedges. Details of the structure and

species richness of each of these layers is provided in the following paragraphs. Please refer to

Appendix B for pictures of historical vegetation structure and composition.

2.4.1 Canopy

The canopy of pine rocklands is dominated by a single species, South Florida slash pine, which

historically ranged in height from approximately 65 to 90 feet (Craighead 1971, Snyder et al.

1990). Diameters of pines historically ranged up to 24 to 30 inches (Craighead 1971, Robertson

1955). Platt et al. (2002) reported pre-Hurricane Andrew pine densities on fragmented pine

rockland sites of between 211 and 975 trees per acre. In the Long Pine Key area of ENP, preHurricane Andrew slash pine densities were recorded at 185 to 477 trees per acre (Snyder et al.

1990) and 294 to 863 trees per acre (Platt et al. 2002). Germination of South Florida slash pine

occurs from October to December. Seedling survival is higher where there is more soil moisture

(McMinn 1970). Seedlings will remain in a fire resistant “grass stage” for two (2) to five (5)

years. While in this grass stage the pines can re-sprout from the root collar after a fire (Ketcham

and Bethune 1963), allowing some to survive. Hofstetter (1973) reported that fires cause an 87%

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

Page 7

mortality of seedlings less than five (5) feet tall and 50% mortality for those 6.6 to 19.8 feet tall.

Seedlings have improved survivability in areas with less duff accumulation (Klukas 1973).

2.4.2 Subcanopy

The subcanopy of pine rocklands consists of a diverse mix of temperate and tropical hardwoods

and palms. Almost 100 native plant species may be present in the subcanopy of Miami-Dade’s

pine rocklands (Bradley, unpublished data). Palms in this layer, all fairly common, include saw

palmetto, cabbage palm, and silver palm, with saw palmetto being the most common and

typically a dominant species in all pine rockland areas. Where pine rocklands historically

experienced seasonal flooding, or had a shallow depth to the water table, cabbage palm becomes

a more dominant species.

Common hardwoods in pine rocklands presently include live oak, poisonwood, southern sumac,

white indigo berry, myrsine, West Indian-lilac, snowberry, nettletree, rough velvetseed, and

willow bustic (Bradley, unpublished data). The ratio of temperate species to tropical species

declines from north to south, with many temperate species becoming absent towards the southern

end of the Miami Rock Ridge, and many tropical species becoming absent to the north. The

subcanopy in the north may resemble a central Florida sandhill more than a pine rockland further

south on the ridge. Historical composition and relative abundance of understory hardwoods may

have differed from current coverage.

In addition to the above hardwoods there are many small shrubs or sub-woody species that can

be conspicuous components of pine rocklands. These include lacy bracken fern, dwarf live oak,

pineland croton, pineland snowberry, partridge pea, and wild sage.

Subcanopy height and density varies temporally and spatially depending on time since fire,

freezes, and distance to rockland hammock communities. Fires, discussed in more detail in

Section 2.6.1 below, historically occur naturally every three (3) to seven (7) years and kill or topkill hardwoods. Freezes and cold weather kill or top-kill more sensitive tropical hardwoods such

as poisonwood and West Indian-lilac (Olmsted et al. 1993). Diversity and stem density of

hardwoods is usually higher in close proximity to rockland hammocks, which serve as a source

for seed rain into the pine rocklands.

No historical data are known that quantified the original density of palms and hardwoods in pine

rockland prior to non-indigenous settlement. Photos from the early 1900s show areas with a very

low palm/shrub layer (less than two feet), but it is difficult to know how representative these

photos are of pine rocklands as a whole (Appendix B). Pine rocklands probably had a subcanopy

layer mostly less than two (2) feet tall. Overall cover of palms and shrubs was probably less thas

25%, with a great degree of patchiness resulting in some very open areas and some very dense

areas.

2.4.3 Herb Layer

Over 225 species of herbs may be found in the pine rocklands of Miami-Dade County (Bradley,

unpublished data). The herb layer consists of forbs, grasses, ferns, and sedges. This herb layer is

much more diverse and has a greater cover where the subcanopy layer is sparse. This herb layer,

much like the subcanopy, consists of temperate and tropical species, but also has a component of

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

Page 8