Ecology of South Florida (EVR 3013) LECTURE 18

UPLAND COMMUNITIES III - HAMMOCKS


MOSS-HUNG OAKS

In ghostly benediction,
Weird fingers
Caress the rich verdure
Of the ageless oaks.

A twilight veil,
Woven on unseen looms
And flecked with misty radiance,
Garlands them

With eerie beauty,
Entwining
Its blue-gray fibres
With the living green.
Etta Josephean Murfrey (1931)[in Jones and O'Sullivan 1995]

I. DEFINITIONS

A. Tree Islands

broader term that includes the following:
  1. bayheads
  2. cypress head or dome
  3. willowhead
  4. pop ash head
  5. tropical hardwood hammock
  6. cabbage palm hammock
  7. oak hammock
  8. tropical hardwood hammock

B. HAMMOCK

1. Definitions

Bed:
  1. rope bed (Arawak)
  2. a swinging couch or bed usually made of netting or canvas and slung by cords from supports at both ends (Webster)
Vegetation:
  1. raised island of vegetation (Arabic)
  2. Hummock - a fertile area in the southern U.S. and especially Florida that is usually higher than its surroundings and that is characterized by hardwood vegetation and deep humus-rich soil (Webster)

C. Etymology

a. Bessey (1911)
Bessey believed hammock was derived from a Seminole word for house, but the Muskogee word for house is chickee.

b. More probable origins
Arawak Indians (From Hispaņola) Arabic
in Columbus's journal via spice trade with Europe
HAMACA (1492) HAMALA (1200 - 1300's)
HAMACA (1513)  HAMMOCK (1556)
(Spanish usage) (English Sailors)
HAMMOCK (modern) HAMMOCKHAMMOCK
(English usage) (mound)(forest)

D. Working definition

Hammocks are broad-leaved, evergreen forests with a closed canopy

E. Classification

1. Topographic

a. low hammocks
b. high hammocks

2. Moisture regime

a. xeric
b. mesic
c. hydric

3. Compositional

a. tropical
b. temperate

4. Canopy dominants

a. oak hammock
b. cabbage palm hammock
c. pigeon plum hammock
d. poisonwood hammock

II. PHYSICAL FEATURES

A. Distribution

1. Elevation

Hammocks are often found on higher ground (more resistant) than surrounding area

2. Historical extent

Craighead estimated that there were once more than 500 hammocks (0.1 -40 ha) on Miami Rockland scattered among pine rockland

3. Successional

Hammocks can be sucessional phases of pine flatwoods, scrub, pine rocklands and beach strand vegetation.

B. Physical Attributes

  1. Usually flat, but do occur on ridges
  2. Topography often irregular due to solution features
  3. Large sinks may be present

C. Geology and Soils

1. Tropical hammocks

Underlain by Pleistocene marine limestones --Miami, Key Largo and Tamiami, Anastasia, and Ft. Thompson Formations

2. Oak hammocks

Oak hammocks are underlain by entisols or spodosols

3. Soils

Shallow with high organic content but often with a well-developed humus layer. Plants often establish in organic matter trapped between solution features. pH of this material is circumneutral.

D. Hydrology

1. Limestone

Well-drained due to limestone solution features

2. Sand

Moderately to poorly drained

3. Swamp

Poorly drained when derived from swamp soils

III. PLANTS

A. Physiognomy

Closed canopy of evergreen broadleaf species

B. Canopy composition, size and density

1. Dominants

sometimes single species, e.g., oak, gumbo limbo, poisonwood

2. Canopy

variable composition, to 20m high

3. Density

To 7500 stems per hectare

4. Dominant species

Dominants include Bursera simarouba (gumbo limbo), Coccoloba diversifolia (pigeon plum), Lysiloma latisliquum (wild tamarind), Metopium toxiferum (poison wood), Quercus virginiana (live oak)

C. Subcanopy and shrub layer

Varibale - may or may not be obvious

D. Herb layer

May be sparse

E. Vines

Vines are often very abundant, especially in disturbed sites

F. Epiphytes

Epiphytes are often abundant, including many ferns, bromeliads, and orchids.

G. Related communities

  1. Mesic oak hammocks <--> pine flatwoods
  2. Xeric oak hammocks <--> scrub
  3. Low hammocks <--> mixed swamps or cypress
  4. Tropical hammocks <--> pine rockland

H. Endemics, exotics, and diversity

1. Endemic species

No endemic species

2. Exotics

Ardisia solanacea shoebutton ardisia
Carica papaya papaya
Dioscorea bulbifera air potato
Jasminum spp. jasmine
Schinus terebinthifolius Brazilian pepper

3. Diversity

Diversity is among the highest at the community level. More than 150 tree species occur in Dade, Collier and Monroe county hammocks.

Species-rich communities
Community Type Total Number of Plant Species
Dry Pineland 303
Hammocks 306
Seasonally Wet Pineland 361


I. Plant species list for hammocks


1. Trees
Live oak Quercus virginiana
Laurel oak Quercus laurifolia
Red bay Persea borboniaC
Dahoon holly Ilex cassine
Orange Citrus sinensisEX & C  [state flower]
Cabbage palm Sabal palmetto  [state tree]
Gumbo limbo Bursera simaruba
Pigeon plum Coccoloba diversifolia
Poison wood Metopium toxiferum
Strangler fig Ficus aurea
Sea grape Coccoloba uvifera
Wild tamarind Lysiloma latiliquum
Jamica dogwood Piscidia piscipula
West Indian mahagony Swietenia mahoganiT

2. Shrubs
Marlberry Ardisia escallonoides
Myrsine Myrsine floridana
Spanish stopper Eugenia foetida
White stopper Eugenia axillaris
Tetrazygia Tetrazygia bicolorT
Rough velvetseed Guettarda scabra
Wild coffee Psychotria nervosa
Brazilian pepper Schinus terebinthifoliusEX
Shoebutton ardisia Ardisia ellipticaEX

3. Epiphytes
Butterfly orchid Encyclia tampensisT
Resurrection fern Pleopeltis polypodioides
Cardinal air plant Tillandsia fasciculataC

4. Vines
Muscadine grape Vitis rotundifolia
Air potato Dioscorea bulbiferaEX

IV. ANIMALS

A. Good habitat for many animal species

B. Animal species list for hammocks

1. Birds
White-crowned pigeon  Columba leucocephalaT
Northern cardinal  Cardinalis cardinalis
Wild turkey  Melagris gallopavo
Red-shouldered hawk  Buteo lineatus
Common flicker  Colaptes auratus
Black vulture  Coragyps atratus
Bluejay  Cyanocitta cristata
Palm warbler  Dendroica palmarum
Gray catbird  Dumetella carolinensis
Red-bellied woodpecker  Melanerpes carolinus
Northern mockingbird  Mimus polyglottos [state bird]
Barred owl  Strix varia
Mourning dove  Zenaida macroura

2. Reptiles
Carolina anole  Anolis carolinensis
Brown anole  Anolis sagreiEX
Black racer  Coluber constrictor
E. diamondback rattlesnake  Crotalus adamanteus
Red rat snake  Elaphe guttata
Southern five-lined skink  Eumeces inexpectatus
Green iguana  Iguuna iguunaEX
Rough green snake  Opheodrys aestivus
Pygmy rattlesnake  Sistrurus miliarius
Box turtle  Terrapene carolina

3. Amphibians
Southern toad  Bufo terrestris
Green tree frog  Hyla cinera

4. Mammals
Opossum  Didelphis virginiana
Gray squirrel  Sciurus carolinensis
Florida panther  Felis concolor ssp. coryiT  [state animal]
Bobcat  Lynx rufus
Raccoon  Procyon lotor
Gray fox  Urocyon cineroargenteus
Florida black bear  Ursus americanus ssp. floridanusT
White-tailed deer  Odocoileus virginanus
Key deer  Odocoileus virginanus claviumT
Wild hog  Sus scrofaEX


5. Spiders
Golden orb weaver  Nephila clavipes
Star spider  Gasteracantha elipsoides

6. Butterflies
Gulf fritillary  Agraulis vanillae
Monarch  Danaus plexippus
Atala  Eumaeus atala
Long-tailed skipper  Goniurus proteus
Zebra longwing  Heliconius charitonius[state butterfly]
Giant swallowtail  Heraclites cresphontes

7. Insects
Freshwater Mosquito  Psorophora confinnis
Black saltmarsh mosquito  Aedes taeniorhynchus
Fire beetle  Pyrophorus spp.
Honey bee  Apis mellifera
Palmetto bug  Periplaneta americana
Lubber Grasshopper  Romalea microptera

8. Gastropods
Tree snail  Liguus fasciatusSSC

9. Crustaceans
Land crab  Gecarcinus lateralis
For superscript by species name: C = commercially exploited, SSC = species of special concern, T = threatened. Florida Game and Freshwater Fish Commission listings. EX = exotic.

V. ECOLOGICAL PROCESSES

A. Fire

Hammocks are relatively fire proof as long as the water table remains within a few feet of the ground surface during the dry season

B. Productivity

gC/ m2/yr = ?

C. Succession

1. Fire

Fire maintains the species composition of pine rocklands

2. Absence of fire

In the absence of fire, hardwood species generally invade. Pines do not regenerate in their own shade

3. Changes in the soil

Successional changes lead to changes in the soil. Organic matter accumulates, shading increases, soil moisture increases and resistance to fire increases

4. Patterns

Hammock species (including Metopium toxiferum, Swietenia mahogoni, Bursera simarouba, and Dipholis salicifolia) increase in the absence of fire.

D. Hurricanes

VI. HUMAN EFFECTS

A. Pre-Colombian

1. aboriginal burning

importance is unknown

2. hunting

3. clearing?

for homesite and agriculture

B. 18th and 19th century

1. Homesites and agriculture

2. Seminole hideouts

3. Development

C. 20th century

1. Wide scale development

2. Drainage and altered fire regimes

3. Exotic species

Back to start,  Back to lecture 10,  11,  12,  13,  14 &15,  16,   17,  On to lecture 19

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