patrickbdevaney/mia9 · Datasets at Hugging Face

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Miami-Dade County. Only twelve elemental occurrences of var. depressa have
Page 3-172
PINE ROCKLANDS Multi-Species Recovery Plan for South Florida
been documented, all in Miami-Dade County. This species has been rapidly
declining due to commercial and residential development that is occurring
throughout its range. In order for this species to avoid extinction, efforts must
be made to preserve existing pine rockland habitat.
The sand flax is endemic to Miami-Dade and Monroe counties. This plant can
be found in solution pits and shallow soils of semi-shaded ephemeral pools on
limerock in open pine rocklands, pineland clearings, and adjacent roadsides
(Long and Lakela 1971). Fire suppression reduces the amount of open areas
required by the sand flax. This plant is State listed as endangered due to the
extreme degree of threats that are occurring as a result of development and
natural occurrences. The sand flax should be managed in a manner that
incorporates fire as a tool to preserve and create open habitat.
The ecotone between pine rocklands and tropical hardwood hammocks is
very important habitat for many plant taxa and is discussed in the Tropical
Hardwood Hammock account.
Ecology
Fire is required for the maintenance of the pine rockland community. It
influences vertical structure and species composition, controls the invasion and
growth of hardwood species, allows light to reach understory and herbaceous
plants, and allows for pine regeneration. Although some have reported that fire
also controls the ratio of pineland to hammock under natural conditions (e.g.
Snyder et al. 1990), others (Olmsted et al. 1983) state that the size and shape of
hammocks remain relatively constant over time. Regardless, under conditions
of fire suppression, hardwoods will invade pine rockland and eventually shade
out pine rockland understory species. For this reason, this plant community has
been termed a fire subclimax community, since hardwood development is
kept in check by fire (FWS 1988b; DERM 1994, 1995).
Pine rockland fires are surface fires that have minimal effects on the pine
canopy. The primary source of natural fire in pine rockland systems is lightning
(Snyder 1986). The majority of lightning-caused fires occur between May and
September, with larger fires in the early part of the wet season (Snyder 1986).
The shortest fire interval could be 2 to 3 years, the longest interval 10 to 15
years with most researchers in agreement that pine rocklands typically burn
twice per decade (Snyder et al. 1990). Hofstetter (1973) estimates a proper fire
frequency at 3 to 7 years, although it has been suggested that a fire interval of
3 to 7 years may be too frequent for young pines to attain a large enough size
to survive a fire (Olmsted and Loope 1984).
The South Florida slash pine is very resistant to fire. Seedlings of the South
Florida slash pine have the ability to resprout from the root collar after a
surface burn, while the northern variety is without this adaptation (Ketcham
and Bethune 1963). It also has long needles which shield apical buds, and a
thick bark which protects the inner bark and cambium (Byram 1948, Hare
1965). Hofstetter (1973) reports an 87 percent mortality of seedlings under 1.5
m (5 ft) tall, and approximately 50 percent mortality of saplings 2 to 6 m (6.6
to 19.8 ft) tall. Pine seedlings have better survival rates in areas of low duff
accumulation, and seedling establishment can be improved when fires occur
Page 3-173
PINE ROCKLANDS Multi-Species Recovery Plan for South Florida
soon before seed release, typically in October (Klukas 1973, Snyder 1986). If
fires occur after seed release then seeds are killed (Snyder 1986).
Many herbs and shrubs resprout or grow rapidly after fire, and shrubs are
seldom killed by a single fire (Snyder 1986). Fire may also stimulate flowering
in these taxa. Fire response may vary dramatically depending on the time of
year of the fire event (Snyder et al. 1990). Gunderson et al. (1983) report that
in a study of fire effects on 36 pine rockland plant species, 21 showed no
alteration in post-fire flowering or fruiting patterns. Species with reduced
flowering or fruiting activity included the eight hardwood shrubs. Six species
exhibited an increase in flowering and fruiting activity in the 9 months
following a fire. Snyder (1986) showed that hardwood recovery was not
affected by season of burning. Instead, recovery was affected by fire intensity.
Gunderson et al. (1983) report that fruiting of shrub species is reduced after a
fire, and that repeated burning may also exhaust root reserves. Almost all herbs
in pine rocklands are perennials which resprout quickly after fires. Snyder
(1986) reported that herbs regained their pre-fire biomass 7 months after a dryseason burn and 1 year after a wet-season burn. Annuals or biennials which do
not resprout following fire include false-foxglove (Agalinis fasciculata) and
tiny polygala.
The theoretical successional relationship between pine rockland and
tropical hardwood hammocks has been much discussed (see Olmsted et al.
1983). It has been reported that in the absence of fire, pine rockland will
succeed to tropical hardwood hammock in 20 to 30 years (Alexander 1967,
Wade et al. 1980, Loope and Dunevitz 1981, Snyder et al. 1990), but that
succession may be slowed if less hammock is present in the vicinity of the pine
rockland (Loope and Dunevitz 1981). Olmsted et al. (1983), however, reported
that hammock size and shape stays remarkably constant over time. Since fire
is a natural function in the South Florida Ecosystem, virtually all hammock
expansion into pine rocklands in the absence of fire would have to be attributed
to anthropogenic factors.
Status and Trends
In Miami-Dade County, this relatively high elevation community was one of the
first to be developed. Land clearing commenced during the late 1800s and early
1900s and continued unabated until 1984, when Miami-Dade County passed the
Tree Protection Ordinance which provided some protection to upland forests.
Prior to modern settlement, this vegetative community covered approximately
65,450 ha (161,660 acres) in Miami-Dade County. As a consequence of
development, the north-south distribution of pine rocklands along the Miami
Rock Ridge has been reduced by more than 12 miles. Approximately 8,029 ha
now remain in Everglades NP. A 1975 inventory (Shaw 1975) recorded 2,132 ha
(5,268 acres) in forest fragments of 2 ha (5 acres) or more outside of Everglades
NP. A 1978 inventory reported a further 25 percent reduction (Loope et al.
1979). DERM (1995) reported that in 1990, 375 pine rockland fragments totaling
nearly 1,780 ha (4,400 acres) remained. These fragments averaged only 4.9 ha
(12.1 acres) in size, and ranged from 0.4 ha (1 acre) to 345 ha (853 acres). Acreage
Page 3-174
PINE ROCKLANDS Multi-Species Recovery Plan for South Florida
of pine rockland on Big Pine Key was reduced from 1,049 ha (2,592 acres) in
1955 to 701 ha (1,732 acres) in 1989 (Folk 1991, Folk et al. 1991). In some cases,
this habitat loss has been the direct cause of plant extirpations [e.g. Carters warea

Miami-Dade County. Only twelve elemental occurrences of var. depressa have

Page 3-172

PINE ROCKLANDS Multi-Species Recovery Plan for South Florida

been documented, all in Miami-Dade County. This species has been rapidly

declining due to commercial and residential development that is occurring

throughout its range. In order for this species to avoid extinction, efforts must

be made to preserve existing pine rockland habitat.

The sand flax is endemic to Miami-Dade and Monroe counties. This plant can

be found in solution pits and shallow soils of semi-shaded ephemeral pools on

limerock in open pine rocklands, pineland clearings, and adjacent roadsides

(Long and Lakela 1971). Fire suppression reduces the amount of open areas

required by the sand flax. This plant is State listed as endangered due to the

extreme degree of threats that are occurring as a result of development and

natural occurrences. The sand flax should be managed in a manner that

incorporates fire as a tool to preserve and create open habitat.

The ecotone between pine rocklands and tropical hardwood hammocks is

very important habitat for many plant taxa and is discussed in the Tropical

Hardwood Hammock account.

Ecology

Fire is required for the maintenance of the pine rockland community. It

influences vertical structure and species composition, controls the invasion and

growth of hardwood species, allows light to reach understory and herbaceous

plants, and allows for pine regeneration. Although some have reported that fire

also controls the ratio of pineland to hammock under natural conditions (e.g.

Snyder et al. 1990), others (Olmsted et al. 1983) state that the size and shape of

hammocks remain relatively constant over time. Regardless, under conditions

of fire suppression, hardwoods will invade pine rockland and eventually shade

out pine rockland understory species. For this reason, this plant community has

been termed a fire subclimax community, since hardwood development is

kept in check by fire (FWS 1988b; DERM 1994, 1995).

Pine rockland fires are surface fires that have minimal effects on the pine

canopy. The primary source of natural fire in pine rockland systems is lightning

(Snyder 1986). The majority of lightning-caused fires occur between May and

September, with larger fires in the early part of the wet season (Snyder 1986).

The shortest fire interval could be 2 to 3 years, the longest interval 10 to 15

years with most researchers in agreement that pine rocklands typically burn

twice per decade (Snyder et al. 1990). Hofstetter (1973) estimates a proper fire

frequency at 3 to 7 years, although it has been suggested that a fire interval of

3 to 7 years may be too frequent for young pines to attain a large enough size

to survive a fire (Olmsted and Loope 1984).

The South Florida slash pine is very resistant to fire. Seedlings of the South

Florida slash pine have the ability to resprout from the root collar after a

surface burn, while the northern variety is without this adaptation (Ketcham

and Bethune 1963). It also has long needles which shield apical buds, and a

thick bark which protects the inner bark and cambium (Byram 1948, Hare

1965). Hofstetter (1973) reports an 87 percent mortality of seedlings under 1.5

m (5 ft) tall, and approximately 50 percent mortality of saplings 2 to 6 m (6.6

to 19.8 ft) tall. Pine seedlings have better survival rates in areas of low duff

accumulation, and seedling establishment can be improved when fires occur

Page 3-173

PINE ROCKLANDS Multi-Species Recovery Plan for South Florida

soon before seed release, typically in October (Klukas 1973, Snyder 1986). If

fires occur after seed release then seeds are killed (Snyder 1986).

Many herbs and shrubs resprout or grow rapidly after fire, and shrubs are

seldom killed by a single fire (Snyder 1986). Fire may also stimulate flowering

in these taxa. Fire response may vary dramatically depending on the time of

year of the fire event (Snyder et al. 1990). Gunderson et al. (1983) report that

in a study of fire effects on 36 pine rockland plant species, 21 showed no

alteration in post-fire flowering or fruiting patterns. Species with reduced

flowering or fruiting activity included the eight hardwood shrubs. Six species

exhibited an increase in flowering and fruiting activity in the 9 months

following a fire. Snyder (1986) showed that hardwood recovery was not

affected by season of burning. Instead, recovery was affected by fire intensity.

Gunderson et al. (1983) report that fruiting of shrub species is reduced after a

fire, and that repeated burning may also exhaust root reserves. Almost all herbs

in pine rocklands are perennials which resprout quickly after fires. Snyder

(1986) reported that herbs regained their pre-fire biomass 7 months after a dryseason burn and 1 year after a wet-season burn. Annuals or biennials which do

not resprout following fire include false-foxglove (Agalinis fasciculata) and

tiny polygala.

The theoretical successional relationship between pine rockland and

tropical hardwood hammocks has been much discussed (see Olmsted et al.

1983). It has been reported that in the absence of fire, pine rockland will

succeed to tropical hardwood hammock in 20 to 30 years (Alexander 1967,

Wade et al. 1980, Loope and Dunevitz 1981, Snyder et al. 1990), but that

succession may be slowed if less hammock is present in the vicinity of the pine

rockland (Loope and Dunevitz 1981). Olmsted et al. (1983), however, reported

that hammock size and shape stays remarkably constant over time. Since fire

is a natural function in the South Florida Ecosystem, virtually all hammock

expansion into pine rocklands in the absence of fire would have to be attributed

to anthropogenic factors.

Status and Trends

In Miami-Dade County, this relatively high elevation community was one of the

first to be developed. Land clearing commenced during the late 1800s and early

1900s and continued unabated until 1984, when Miami-Dade County passed the

Tree Protection Ordinance which provided some protection to upland forests.

Prior to modern settlement, this vegetative community covered approximately

65,450 ha (161,660 acres) in Miami-Dade County. As a consequence of

development, the north-south distribution of pine rocklands along the Miami

Rock Ridge has been reduced by more than 12 miles. Approximately 8,029 ha

now remain in Everglades NP. A 1975 inventory (Shaw 1975) recorded 2,132 ha

(5,268 acres) in forest fragments of 2 ha (5 acres) or more outside of Everglades

NP. A 1978 inventory reported a further 25 percent reduction (Loope et al.

1979). DERM (1995) reported that in 1990, 375 pine rockland fragments totaling

nearly 1,780 ha (4,400 acres) remained. These fragments averaged only 4.9 ha

(12.1 acres) in size, and ranged from 0.4 ha (1 acre) to 345 ha (853 acres). Acreage

Page 3-174

PINE ROCKLANDS Multi-Species Recovery Plan for South Florida

of pine rockland on Big Pine Key was reduced from 1,049 ha (2,592 acres) in

1955 to 701 ha (1,732 acres) in 1989 (Folk 1991, Folk et al. 1991). In some cases,

this habitat loss has been the direct cause of plant extirpations [e.g. Carters warea