Florida's Plant Communities and Bromeliad Habitats

[i]Florida's Plant Communities and Bromeliad Habitats

South Florida has a subtropical climate, with pronounced wet and dry seasons. A mixture of temperate and tropical plants and animals occur in a variety of communities. South Florida lies at or just slightly above sea level, and changes in altitude of only a few feet can result in dramatic changes in associated plant comunities.

The Everglades region is primarily a saw-grass marsh, within which slight elevations in its limestone rock foundation, called hammocks, support communities of tropical hardwoods, which in turn support many of the state's native bromeliads. Bromeliads can also be found in sloughs (slightly deeper and wetter areas) containing cypress swamps, in dwarf cypress domes among the prairie ecosystem, or in the dryer, upland pine flatwoods. Large areas of these unique communities are protected in parks in southern Florida, but development and man-made hydrological changes have threatened many of the areas not under public control.



Epiphytic bromeliads have a highly restricted habitat preferences, in large part based on their ability to absorb mineral nutrients from specific environments. Dome species are only found where canopy and humidity conditions are just right. Bromeliads generally prefer moist habitats that are well lit, although requirements vary by species. Many species are most commonly found near rivers, lakes, and ponds.

Bromeliads will rarely colonize all potential host plants within a habitat. Florida's species of Tillandsia are often found on oak and cypress trees, whose rough bark provides a suitable substrate for seedling attachment, as well as on hackberry trees. Hackberry and live oak trees have many spreading branches that provide a large area for epiphytic growth. Tillandsias generally prefer host trees that branch considerably, have a thick, rough bark with enough crevices to hold seeds, and do not produce chemicals (alleopathic substances) unfavorable for seedling growth. For example, seedlings are not able to develop on many tropical trees such as camphor because of the chemicals produced by the trees.

Florida's threatened and endangered bromeliads occur in the following communities, as defined by the Florida Natural Areas Inventory:



Epiphytes

Epiphytes are plants that live on other plants but do not take any food from them (they are not parasitic). Many kinds of bromeliads, orchards and ferns are found as epiphytes and may be very common in tropical rain forests. In temperate (colder) climates, some algae, lichens and mosses may grow as epiphytes.

Epiphytes may live high in the tree branches (in the canopy) and may also be attached anywhere along the trunk of a suitable tree. Most are found lower in the lower branches, where they are shaded. Most epiphytes can grow on more than one species of tree and even on rocks or telephone wires. Epiphytes produce many seed's beccause most will fall to the ground and die without lodging within the tree canopy.
This growth habit also presents several problems. If the branch on which the epiphyte is growing is broken from the tree by the wind, the epiphyte then falls to the ground with the branch. A larger problem is getting water and nutrients. An epiphyte's roots serves to anchor it to its host tree, and not to absorb water and food. Some epiphytes receive the water they need from rain, others from dew and mist.

Some bromeliads have special absorbing scales (trichomes) that allow them to take in water and nutrients through their leaves. Many epiphytes are adapted to hold water in cavities, between leaves, or in special cells. Other epiphytes (algae, lichens and mosses) can survive long periods without water.
Whether they live in cold or warm climates and under dry or moist conditions, all epiphytes are adapted to their unusual way of life. They are able to survive without soil, sometimes high from the ground, under extreme conditions. The many different kinds of epiphytes have produced a great many adaptations for their environment, and epiphytes contribute substantially to the rich biological diversity found in the canopies of humid tropical forests.



Florida's Bromeliads

Bromeliads are members of the pineapple fanily (Bromeliaceae). They are often called airplants, because while some may grow terrestrially (on the ground), most are epiphutes, growing attached to tree trunks and branches. Epiphytic bromeliads do not harm their host tree. They absorb through their leaves the water and nutrients they need from the air and rain that falls through the canopy and becomes enriched with nutrients along the way.
Many bromeliads collect water between their leaves, serving as a habitat for small animals and a water source in drier months. In addition to their important ecological roles, their unusual form and colorful flowers are an added attraction to the visitors of Florida's many parks and natural areas. Their value is often overlooked, and their loss would be an immeasurable tragedy for the state.

Bromeliads are primarily tropical plants, and most of the species found in Florida prefer warm and humid conditions. The frequent short rains in south Florida during many months, the plant's ability to withstand dry conditions for long periods, and the geological conditions that maintain humidity in the drier months in south Florida all contribute to bromeliad growth.. In addition, the mixture of tropical and temperate plants in south Florida's hammocks and swamps provides the appropriate canopy conditions needed by some species.

Distribution of bromeliads in Florida is primarily determined by temperature condotions. Frost limits most of the state's native bromeliads, and during years of severe cold weather, populations of cold-senitive species can be reduced substantially. At least every decade or two, severe frost kills back populations of bromeliads in north and central Florida, establishing the northern range limits on the species occuring there. Florida's rarest bromeliads (Guzmania monostachia, Catopsis floribunda, and Catopsis berteroniana) are restricted to the southernmost region of the state. These species also have very specific humidity and shade requirements, restricting them to certain habitats with appropriate canopy and geological conditions.

Of Florida's 16 species, 13 are not found elsewhere in the United States, and one (Tillandsia simulata) is precinctive to Florida (found nowhere else). Florida populations of bromeliads are distinct from the West Indian populations from which they originated. There is also genetic variation among populations of certain species within Florida, particularly Tillandsia fasciculata. All of Florida's native species of bromeliads are epiphytic, although some species may sometimes be found growing terrestrially (Tillandsia utriculata and Tillandsia fasciculata).



The Value of Bromeliads to Florida

Bromeliads are important components of the ecosystems in which they are found. Water accumlates between the leaf axils, especially in the larger tank bromeliads, and many small animals live in what to them are like ponds. The base of large leaf axils of mature Tillandsia utriculata may contain water throughout the year in southern Florida, and up to a quart of water has been measured from large plants of this species in the state. Several insect and worm species depend on bromeliads in Florida for their survival, and larger animals such as frogs, snakes and salamanders use these plants for protection and as a water source.
Even non-tank bromeliads provide protection for a number of insect and other invertebrate species. Dozens of spiders and insects hide within masses of Spanish moss as resting sites during the day. Spanish moss also constitutes a significant portion of the nests of several bird species. Owls may also nest occasionally in some bromeliad species..... the great horned owl (Bubo virginianus) has been observed nesting on top of clumps of Tillandsia fasciculata in Florida.

Bromeliads in Florida contribute to a rich biological diversity found in the state's unique ecosystems. Seeds of bromeliads orignally blew in from the West Indies to establish Florida's bromeliad populations, but the plants have been in Florida so long they have become naturalized, adapting to the local environment. Their populations are genetically distinct from those of the same species in the West Indies from which they came. For example, Guzmania monostachia populations in Florida prefer shady locations and are never seen in the exposed upper canopy, the prefered location of populations of the same species in Central America and the Caribbean. The conservation of bromeliads in Florida contributes to the overall conservation of bromeliad biodiversity.

In addition to their important ecological roles, Florida's bromeliads are an aesthetic addition to the state's many parks and natural areas.
The Florida State Park Service recently received the National Gold Medal State Park Award for Excellence designating the Florida Park System as "America's Best Parks." During 2002 - 2003 there were 16.7 million visitors to Florida's state parks, which are the No. 2 destination for air visitors to Florida. The overall direct economic impact of the state park system on local economies was nearly $476 million in 2002 -2003. Bromeliads adorn most of the national, state, and county parks in Florida, contributing substantially to the unique natural features that attract so many visitors each year. Their conservation is of consequence to the growing trend of the ecotourism activities in the state.

Finally, epiphytic bromeliads provide an exceptional opportunity for teaching about many biologicaland environmental themes. In addition to analyzing such concepts as how epiphytic plants can survive in treetops without soil and how the water they collect serves as a home to different kinds of animals, students can appreciate some of the natural treasures of their state and come to understand how easily they can be lost forever. Trachers from elementary to college level and local environmental educators have been bringing groups to the Myakka River State Park for hands-on experiences with these distinctive plants and to see the threats they are facing.
Opportunities exist for similar programs at other bromeliad-rich parks. Conservation of the state's bromeliads ensures that teachers and environmental educators have continued access to this valuable rescource when using parks for hands-on education.

Florida's native bromeliads are a valuable component of Florida's unique ecosystems, and their loss would be significant, not only in ecological terms but also in terms of the loss of educational opportunities and aesthetic pleasure that native epiphytes provide to visitors of natural areas. The conservation of native bromeliads in parks and other protected areas is a priority. It is both desirable for the enjoyment of the many visitors to Florida's parks and necessary for the preservation of the state's endangered and threatened bromeliad species, given the ever-increasing encroachment of human populations on non-protected lands throughout south Florida.



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