patrickbdevaney/mia9 · Datasets at Hugging Face

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(Hodanish et al. 1997), ignition probably occurred most frequently in the spring when vegetation
was at its driest (Beckage et al. 2003). Since lightning strikes can occur year-round (Hodanish et
al. 1997), fires probably occurred throughout the year, but more frequently in the spring and/or
summer when lightning is much more frequent.
Long-term temporal patterns of fire occurrence were probably influenced by El Niño induced
climate oscillations, resulting in very short times between fires during some decades, and very
long intervals in other decades (Beckage et al. 2003). Periods of short intervals may have been
important in reducing shrub biomass. Longer intervals may have allowed for pine seedlings to
grow and reach canopy height, which 3-7 year fire intervals may have prevented (Olmsted and
Loope 1984).
Fires set by indigenous people may have also influenced pine rocklands and may have differed
from theoretical natural fire regimes (Pyne et al. 1982). Fires may have been set by Tequesta
Indians to assist hunting efforts and maintain coontie, an important food source (Van Essen
2006). The amount, type, and seasonality of aboriginal burning are unknown.
2.6.2 Tropical Cyclones
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. These storms can also bring large amounts of rainfall in
very short time periods and cause regional flooding.
Tropical cyclones can have significant impacts on pine rocklands. Strong winds can topple pine
trees. On Long Pine Key in ENP, Hurricane Andrew caused the deaths of 20 to 32% of pine trees
in the two (2) years after the storm, with local mortality ranging from only 3 to 4% up to 50 to
60% (Platt et al. 2000). Larger pine trees were more likely to be killed than smaller trees (Platt et
al. 2000). Hurricane Donna in 1960 is reported to have snapped or toppled one (1) to two (2)
Fire in pine rocklands
Photo by Keith Bradley, IRC
EEL Program, Management Plan, Part II – Pine Rockland (DRAFT) _____________________________________________________________________________________________________________________
Page 11
pine trees per acre on Long Pine Key (Craighead 1971). Hurricane Andrew also toppled,
defoliated, or top killed understory hardwoods, reducing subcanopy densities.
Hurricanes can also cause high storm surges, which can temporarily flood coastal pine rocklands.
Salt damage can kill vegetation, including trees, palms, hardwoods, and herbs. In 1992,
Hurricane Andrew’s storm surge reached almost 17 feet at the Deering Estate South Addition
and EEL site, covering pine rocklands. In addition to the pine rockland being flooded, a five (5)
to ten (10) foot tall and 15 to 30 foot wide rack line of dead vegetation and debris was deposited
in the pine rockland. The area covered by the rack line has now succeeded from pine rockland to
a dense shrubland covered by hardwoods, which invaded the rich organic soils left by the
decomposing debris.
2.6.3 Freezes
Freezes and cold weather kill or top-kill many plant species in pine rocklands, especially tropical
hardwoods (Olmsted et al. 1993). Because some pine rocklands can have a large component of
tropical species, freezes can have a major impact, at least temporarily. Freezes can be very
beneficial in removing living hardwood biomass (FNAI and FDNR 1990), but will leave a large
amount of dead woody matter. This dead material is later removed by fires.
2.7 Rare Organisms
Plant and animal species in any ecosystem range from abundant to extremely rare, even under
completely natural conditions. Prior to non-indigenous settlement, some plant and animal species
in pine rocklands were undoubtedly rare even before major human influences. Because botanical
exploration did not start in Miami-Dade County with any significance until the late 1800s, and
poor data was collected even then, we will never fully know the historical abundance of most
plant species. It is also likely that some plant species were never recorded by any botanist and
were lost due to habitat destruction or disturbance without the knowledge of the botanical
community. Examples of plant species that may have been historically rare include Bahama
manjack and Carter’s orchid.
EEL Program, Management Plan, Part II – Pine Rockland (DRAFT) _____________________________________________________________________________________________________________________
Page 12
3.0 Current Conditions, Threats, and Trends
This section discusses the current state of the pine rockland ecosystem in Miami-Dade County
including not only the properties owned and/or managed by EEL, but those owned by other
public entities and private landowners.
3.1 Current Distribution of Pine Rocklands
The distribution of the pine rockland ecosystem has declined dramatically following nonindigenous settlement. At present conditions, almost 84% of the historic Miami Rock Ridge
(approximately 126,500 acres), is now covered by agriculture, suburban lands, or urban lands,
with only small isolated areas of natural vegetation still existing. The remaining portion of the
ridge (approximately 24,500 acres) is located within ENP (Figure 2). A survey conducted from
2004 to 2005 of all remaining forest fragments in Miami-Dade County outside of ENP found that
only 1.8% of the historical extent of pine rocklands remained (Bradley, unpublished data). Only
2,273 acres of the historical estimate acreage of pine rocklands were found to remain. The
geographic range of pine rocklands has been reduced as well – the northern 12 miles of the
Miami Rock Ridge have been completely developed.
In 2005 there were 126 pine rockland fragments in Miami-Dade County outside of ENP
(Bradley, unpublished data). These fragments ranged from 0.25 acres to 800 acres, with a mean
size of 15.6 acres and a median size of 4.3 acres. Figure 2 shows the current versus historical
pine rockland habitat distribution in Miami-Dade County.
3.2 Physiography
Today’s level of human population and urban development in Miami-Dade County was made
possible by a significant effort to drain the landscape. This drainage and dewatering process
brought about other changes that are briefly discussed in the following sections.
3.2.1 Soils
Pine rockland soils are generally unchanged from historical conditions. Because the dominant
substrate of pine rocklands is oolitic limestone, there is little that can be done to it. Pockets of
soil, either quartz sand or loam, cannot erode because they are in depressions in the limestone.
The largest change to pine rockland soils is the accumulation of duff and usually organic soil on
fire suppressed sites. Under historical conditions, periodic fires limited the growth of hardwood
species that produced leaf litter, and also burned any that did accumulate. On many sites this
organic layer is now several inches thick and completely covers the limestone substrate.
Soils may have also changed in pine rocklands that previously flooded for short periods during
the summer rainy season. Dry conditions tend to reduce organic accumulations, principally
because of the lack of protective soil moisture and increased combustion in fires.
EEL Program, Management Plan, Part II – Pine Rockland (DRAFT) _____________________________________________________________________________________________________________________
Page 13
EEL Program, Management Plan, Part II – Pine Rockland (DRAFT) _____________________________________________________________________________________________________________________
Page 14
3.2.2 Hydrology
The historical hydrology of Miami-Dade County has been dramatically and permanently altered.
The water table throughout the county has dropped due to wide-scale drainage projects (see Part
I of this management plan). The water table has decreased throughout the entire range of pine
rocklands. For many forest fragments at high elevations, this is probably not of ecological
significance. Some pine rocklands, however, were close to the water table and probably flooded

(Hodanish et al. 1997), ignition probably occurred most frequently in the spring when vegetation

was at its driest (Beckage et al. 2003). Since lightning strikes can occur year-round (Hodanish et

al. 1997), fires probably occurred throughout the year, but more frequently in the spring and/or

summer when lightning is much more frequent.

Long-term temporal patterns of fire occurrence were probably influenced by El Niño induced

climate oscillations, resulting in very short times between fires during some decades, and very

long intervals in other decades (Beckage et al. 2003). Periods of short intervals may have been

important in reducing shrub biomass. Longer intervals may have allowed for pine seedlings to

grow and reach canopy height, which 3-7 year fire intervals may have prevented (Olmsted and

Loope 1984).

Fires set by indigenous people may have also influenced pine rocklands and may have differed

from theoretical natural fire regimes (Pyne et al. 1982). Fires may have been set by Tequesta

Indians to assist hunting efforts and maintain coontie, an important food source (Van Essen

2006). The amount, type, and seasonality of aboriginal burning are unknown.

2.6.2 Tropical Cyclones

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. These storms can also bring large amounts of rainfall in

very short time periods and cause regional flooding.

Tropical cyclones can have significant impacts on pine rocklands. Strong winds can topple pine

trees. On Long Pine Key in ENP, Hurricane Andrew caused the deaths of 20 to 32% of pine trees

in the two (2) years after the storm, with local mortality ranging from only 3 to 4% up to 50 to

60% (Platt et al. 2000). Larger pine trees were more likely to be killed than smaller trees (Platt et

al. 2000). Hurricane Donna in 1960 is reported to have snapped or toppled one (1) to two (2)

Fire in pine rocklands

Photo by Keith Bradley, IRC

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

Page 11

pine trees per acre on Long Pine Key (Craighead 1971). Hurricane Andrew also toppled,

defoliated, or top killed understory hardwoods, reducing subcanopy densities.

Hurricanes can also cause high storm surges, which can temporarily flood coastal pine rocklands.

Salt damage can kill vegetation, including trees, palms, hardwoods, and herbs. In 1992,

Hurricane Andrew’s storm surge reached almost 17 feet at the Deering Estate South Addition

and EEL site, covering pine rocklands. In addition to the pine rockland being flooded, a five (5)

to ten (10) foot tall and 15 to 30 foot wide rack line of dead vegetation and debris was deposited

in the pine rockland. The area covered by the rack line has now succeeded from pine rockland to

a dense shrubland covered by hardwoods, which invaded the rich organic soils left by the

decomposing debris.

2.6.3 Freezes

Freezes and cold weather kill or top-kill many plant species in pine rocklands, especially tropical

hardwoods (Olmsted et al. 1993). Because some pine rocklands can have a large component of

tropical species, freezes can have a major impact, at least temporarily. Freezes can be very

beneficial in removing living hardwood biomass (FNAI and FDNR 1990), but will leave a large

amount of dead woody matter. This dead material is later removed by fires.

2.7 Rare Organisms

Plant and animal species in any ecosystem range from abundant to extremely rare, even under

completely natural conditions. Prior to non-indigenous settlement, some plant and animal species

in pine rocklands were undoubtedly rare even before major human influences. Because botanical

exploration did not start in Miami-Dade County with any significance until the late 1800s, and

poor data was collected even then, we will never fully know the historical abundance of most

plant species. It is also likely that some plant species were never recorded by any botanist and

were lost due to habitat destruction or disturbance without the knowledge of the botanical

community. Examples of plant species that may have been historically rare include Bahama

manjack and Carter’s orchid.

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

Page 12

3.0 Current Conditions, Threats, and Trends

This section discusses the current state of the pine rockland ecosystem in Miami-Dade County

including not only the properties owned and/or managed by EEL, but those owned by other

public entities and private landowners.

3.1 Current Distribution of Pine Rocklands

The distribution of the pine rockland ecosystem has declined dramatically following nonindigenous settlement. At present conditions, almost 84% of the historic Miami Rock Ridge

(approximately 126,500 acres), is now covered by agriculture, suburban lands, or urban lands,

with only small isolated areas of natural vegetation still existing. The remaining portion of the

ridge (approximately 24,500 acres) is located within ENP (Figure 2). A survey conducted from

2004 to 2005 of all remaining forest fragments in Miami-Dade County outside of ENP found that

only 1.8% of the historical extent of pine rocklands remained (Bradley, unpublished data). Only

2,273 acres of the historical estimate acreage of pine rocklands were found to remain. The

geographic range of pine rocklands has been reduced as well – the northern 12 miles of the

Miami Rock Ridge have been completely developed.

In 2005 there were 126 pine rockland fragments in Miami-Dade County outside of ENP

(Bradley, unpublished data). These fragments ranged from 0.25 acres to 800 acres, with a mean

size of 15.6 acres and a median size of 4.3 acres. Figure 2 shows the current versus historical

pine rockland habitat distribution in Miami-Dade County.

3.2 Physiography

Today’s level of human population and urban development in Miami-Dade County was made

possible by a significant effort to drain the landscape. This drainage and dewatering process

brought about other changes that are briefly discussed in the following sections.

3.2.1 Soils

Pine rockland soils are generally unchanged from historical conditions. Because the dominant

substrate of pine rocklands is oolitic limestone, there is little that can be done to it. Pockets of

soil, either quartz sand or loam, cannot erode because they are in depressions in the limestone.

The largest change to pine rockland soils is the accumulation of duff and usually organic soil on

fire suppressed sites. Under historical conditions, periodic fires limited the growth of hardwood

species that produced leaf litter, and also burned any that did accumulate. On many sites this

organic layer is now several inches thick and completely covers the limestone substrate.

Soils may have also changed in pine rocklands that previously flooded for short periods during

the summer rainy season. Dry conditions tend to reduce organic accumulations, principally

because of the lack of protective soil moisture and increased combustion in fires.

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

Page 13

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

Page 14

3.2.2 Hydrology

The historical hydrology of Miami-Dade County has been dramatically and permanently altered.

The water table throughout the county has dropped due to wide-scale drainage projects (see Part

I of this management plan). The water table has decreased throughout the entire range of pine

rocklands. For many forest fragments at high elevations, this is probably not of ecological

significance. Some pine rocklands, however, were close to the water table and probably flooded