Florida Forestry Information |
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| Introduction |
A wide variety
of soils and landscapes comprise the state of Florida. These include:
Soil is the portion of the earth's crust in which plants can grow if water and temperature are adequate, at least the minimum nutrients are available, and toxic substances are in low concentration. All soils develop from weathered rock, volcanic ash deposits, or accumulated plant residues. The majority of soils are formed from weathered minerals which include:
Soils are often deposits of weathered, loosened, or transported particles. These materials are called parent materials and are deposited by water (alluvium), glaciers (moraines), wind (dunes), or gravity (colluvium). These deposits (in parentheses above) are called landforms. |
| Soil Biology |
| When the complex
of rock and plant residues described above is occupied and modified by living
organisms, the dynamic system that we know as soil develops. The term soil biota refers to the organisms that spend all or a part of their life cycle in the soil. They can be divided into
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| Soil Flora |
| Soil flora
refers to a very diverse group of nonanimal organisms that include:
Bacteria Bacteria are classified (ecologically) as:
Actinomycetes are
a group of organisms that are sometimes (incorrectly) grouped with fungi.
They have characteristics of both fungi and bacteria, having branching
hyphae which are often brightly colored.
Fungi make up the
majority of the decomposer organisms in many forest soils. Perhaps
the most significant group of fungi are those that form symbiotic mycorrhizal
associations with tree roots. These mycorrhizae increase the
efficiency with which nutrients, which are at very low concentrations in
the soil, are uptaken by plants.
Free-living algae
live at the interface of the soil and the atmosphere. Blue-green
algae are capable of nitrogen fixation (conversion of atmospheric nitrogen
into usable form for plants).
Roots play an important role in soil development and function. Organic matter is contributed to the lower soil horizons when roots die, promoting the formation of soil structure. The channels left in the soil after roots have decayed improve soil aeration and facilitate the movement of water. Roots also increase the weathering rate of minerals and rock because of organic compounds they secrete or because of the activities of the microorganisms that live in the rhizosphere (the root zone). |
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| Soil Fauna |
| Soil fauna include all animals that
spend at least part of their life in the soil. They are a very diverse
group, ranging from moderately large animals that excavate underground
burrows, to microscopic mites, nematodes, and protozoans that reside in
the films of water coating soil particles.
Soil Invertebrates The burrowing activities of soil invertebrates
influence soil aeration and structure, soil drainage, and soil development.
Mollusks are more abundant in richer soils, where calcium needed for their metabolism is abundant. Earthworms These animals are responsible for large-scale
soil mixing. This takes surface organic matter deep into the mineral
soil, promoting soil structure and bringing minerals from lower horizons
to the soil surface.
Termites play a major role in many tropical
soils as soil mixers and, as earthworms do, aid in the incorporation of
organic matter.
Ants alter the bulk density of soils.
In areas of high activity significant quantities of material are brought
to the surface from lower horizons. This material accumulates at
the surface and after a prolonged period it forms the surface of the mineral
layer. As predators they affect the composition of the soil fauna.
Mites are one of the most numerous groups
of animals in the soil, with numbers as high as 10,000 individuals per
square meter. They exist mainly in the organic surface layers where
they play a major role in decomposition. They also eat bacteria and
fungi.
These animals are another abundant group
in the organic surface layers. They have been reported to reach densities
of 50,000 individuals per square meter in a Douglas fir plantation.
They feed on living and dead plant material, feces, bacteria, and algae.
Potworms are small white worms that can
reach densities of 250,000 individuals per square meter. They eat
dead organic matter and small feces. They ingest small mineral particles
and probably play an important role in mixing organic matter into the mineral
soil.
These animals are small roundworms that are best known for their parasitism of plants and are not known to be involved in the decomposition of organic matter. |
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| The Origin of Florida's Soil Materials |
The Florida plateau
consists of the present peninsula plus a submerged shelf
in the Gulf of Mexico that extends the length of the state. From
about 100 million to 20 million years ago, the Florida peninsula existed
in an environment similar to today's Bahaman Banks, where pure limestone
and dolomite rocks were deposited.
From about 25 to
20 million years ago, changes associated with mountain formation throughout
the Gulf coast caused streams to bring deposits of sand, clay, marl, phosphatic
boulders, and limestone on top of the Florida aquifer.
*Sinkholes are formed by solution of limestone near the surface and consequent collapse of the overlying material into the solution cavities. If surface runoff carries clay sediments into the depression, a lake or marsh may form. Sinkholes are rare where the sedimentary cover over the limestone is more than about 60 meters thick. |
| Physiographic Subdivisions of Florida |
| The physiography of Florida is
the result of erosion, deposits, and solution-related processes that have
formed the land over time. There are ten major physiographic subdivisions
in Florida:
1- Sea Island District:
The sea island district of northeastern Florida ranges from upland terraces
to plains and ridges. Soils are dominantly sandy but significant
expanses of clayey deposits exist. The ecosystems associated with
this district include pine flatwoods, dunes, and salt marshes.
3 - Gold Coast - Florida Bay District: This is a uniformly low-lying district and includes the area of slow south and southwestward drainage from Lake Okeechobee (the Everglades), with coastal ridges, mangrove swamps, and the Florida Keys. Parent material is largely limestone rock with a sand, marl, and organic material covering. The ecosystems associated with this district include marshes, dwarf cypress, prairies, rocklands, and mangroves. 4 - Southwestern Flatwoods District: Located on the southwestern corner of the peninsula, the landscapes of this district include low plateaus and ridges, flatwoods, prairies, rockland/marl plains, and a variety of coastal features. Soils are sand, clay, limestone, and organic deposits. The ecosystems associated with this district include pine flatwoods, prairies, cypress ponds, mangroves, and dunes. 5 - Central
Lake District: This district is
made up of sandhills and lakes typical of the central Florida ridge.
It is a sandhill karst terrain with many solution basins. The permeable
sands and rapid internal drainage of this region make it the principal
recharge area of the Florida aquifer. Soils are sand, clay, and organic
deposits. The ecosystems associated with this district include sandhills
and sand pine scrub.
7 - Tifton
Upland District: Located in the
north central portion of the Florida Panhandle, this upland district's
topography is controlled by thick deposits of sediments that have been
sculptured by surface drainage. Soil materials are clay or loam,
topped by a varying thickness of sand. The ecosystems associated
with this district include pine and mixed hardwood forests.
10 - Southern Pine Hills District: This district is located in the far western portion of the Panhandle, this district is an area of thick sediments. The northernmost, highest sections are stream-sculptured from an alluvial plain over a layer of sand, gravel, silt, and clay. Intermediate elevations consist of ridges formed by coastal sediments, and the coastal strip consists of relic lagoon and barrier island features. Soil materials are loam and clay to the north with an increasing thickness of sand toward the southern part of the district. The ecosystems associated with this district include pine and mixed hardwood forests, sandhills, and dunes. |
| Management Considerations |
| Soil is the least renewable physical component of the forest ecosystem.
Once lost it is probably the most difficult resource to replace. Much
of the very fertile soil on moderate topography in climates suitable for
high-production forestry have been claimed by agriculture. Our need
for food has traditionally outweighed our need for forest products.
Thus foresters and private nonindustrial forest (PNIF) landowners are frequently
left with less productive soils. Due to this limitation, foresters generally have fewer options for manipulating soil physical and chemical properties than does the farmer. Foresters can fertilize some types of sites and use fire or mechanical site preparation to improve the fertility of the land after harvesting, but trees generally must be grown with the soil resource we have inherited or purchased.
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| Soil Disturbance |
| Disturbances to the soil from harvesting can vary from
a slight disturbance to the forest floor to complete loss of the upper
soil horizons. The degree of ground disturbance is determined by
the type of harvesting equipment used and the time of year harvesting
takes place. Level of Soil Disturbance Associated with Different Types of Harvesting Equipment The least soil disturbance occurs with skyline yarding, a harvesting method in which logs are moved from the stump to the landing (where logs are loaded onto trucks) suspended in the air by a taut cable. High lead yarding, the most common harvesting method on the west coast, disturbs the soil significantly more than skyline yarding. In this method the logs are dragged to a central landing by a slack cable, and there is considerable soil disturbance on the yarding roads. The highest degree of disturbance is associated
with tractor or skidder yarding. This method involves
a wheeled or tracked vehicle dragging the log from the harvesting site
to the landing by a cable. In more northern climes, disturbances to the soil can be minimized by harvesting during the winter months when snow acts as a protective layer over the soil. In Florida this is not an option.
Disturbance to the soil can be minimized by scheduling harvesting activities during the dry season when the soil is less likely to by moved or altered by heavy equipment. |
| Effects on Soil Stability |
| On steep slopes, the stability of the soil may be significantly reduced to the point where mass soil movement occurs (slides, slumps, and debris avalanches). The topography of Florida rarely lends itself to these types of effects, but there are some areas, particularly on the Panhandle, where consideration to mass soil movement is appropriate. |
| Alteration in Soil Temperature |
| Changes in soil
temperature occur as a result of clearcutting. The extent of these
changes depends on the degree of mineral soil exposure and the reduction
in the depth of the surface organic matter accumulation.
Roots are largely confined to the surface organic layers. Where these layers contain nutrient-poor material, the plants will experience inadequate nutrition and grow very slowly. The restriction of roots to the surface of the forest floor, which may dry out during the dry period, make seedlings susceptible to drought injury or death. Exposure of mineral soil reduces temperature extremes at the soil surface which can be beneficial to plants, but in environments with hot summers, soil temperatures may increase to levels that are lethal for many plants. |
| Alteration of Soil Physical Properties |
Use of heavy machinery
can alter:
Some findings: In one study on the impacts of forest operations on soil physical properties, soil density increased exponentially with increasing number of passes of a tractor. One pass of a tractor on wet soil resulted in as much compaction as four trips on a dry soil!
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| Take-Home Message |
It is important to remember that in most
cases the productive potential of the site is vested in a relatively thin
surface layer of soil. Erosion of only a few centimeters of this surface
layer may be accompanied by significant reductions in plant growth.
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| References
Fisher, R.F., A.S. Jenson, D.M. Post, D.L. Rockwood, W.H. Smith, and E.T. Sullivan. Forest Management for Small Ownerships. Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville. 33 pp. Kimmons, J.P. 1987. Forest Ecology. Macmillan Publishing Company, N.Y. 531 pp. Miller, R.W. and R.L. Donahue. 1990. Soils: An Introduction to Soils and Plant Growth. Prentice Hall, Inc., Englewood Cliffs, N.J. 768 pp. Myers, R.L. and J.J. Ewel (editors). 1990. Ecosystems of Florida. University of Central Florida Press, Orlando, Florida. 765 pp. To order Ecosystems of Florida, write to:
Pritchett, W.L. and J.W. Gooding. 1975. Fertilizer Recommendations for Pines in the Southeastern Coastal Plain of the United States. Agricultural Experiment Stations, Institute of Food and Agricultural Sciences, University of Florida, Gainesville. |
Autotrophic:
satisfy energy needs by utilizing energy released during transformations
of inorganic compounds.