| The types of vegetation
found in each region of the wetland are based on what stage of creation/deterioation
is occurring there. The dynamic nature of the deltaic cycle leads
to rapid changes in soil stability, salinity, and subsequently vegetation
type in the active zone of the marsh. The remainder of the marsh
is much more stable and exists along a salinity gradient. The marshes
begin with the barrier islands and move inland to the bottomland hardwood
swamps. |
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A majority of the Louisiana
coastal wetlands are classified as intertidal marshes. Intertidal
marshes are the most abundant landform on the coastal plain, covering approximately
10,192 square kilometers. Intertidal marshes consist of salt, brackish,
and freshwater vegetation types with the species richness increasing with
freshness. This is due to only a few species being able to tolerate
the stresses of both flooding and salinity. The vegetation found in
the coastal marshes can be loosely categorized into groups based on location
within the marsh. Many species overlap into different the different
zones especially along tidal creeks or raised landforms. |
| Barrier islands: typically low
and sandy with poorly developed dunes. The vegetation consists primarily
of salt tolerant xeric grasses and succulent herbs on the dunes
grading into salt marsh vegetation on the inland and Gulf sides. Some
ancient barrier islands exist in the Chenier plains and used to be home
to Live oak forests that have mostly been lost to subsidence and development. |
| Smooth Cordgrass: Present
in highly saline regions with wave action, most common on seaward edge
of barrier islands |
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| Wiregrass: Most
common on higher land on barrier islands |
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| Saltwort: Very salt
tolerant, often found in low spots on and around barrier islands
where evaporation leads to high salt concentrations |
|
| Glasswort: Found both
on barrier islands and mixed in with grasses in the salt marshes. Likes
low, alkaline, salty locations |
|
| Black Mangrove: rare,
but found along the edges of the barrier islands. Growth is very
stunted due to high frost intolerance |
|
| Live oak: Large populations
were once found on ancient levees and other elevated landforms in the Chenier
plain. |
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Salt Marshes: Found
at the coastal edge of the wetland complex and cover approximately 1650
acres. They are characterized by daily tidal flushing that is also
behind the creation of bidirectional stream channels throughout the tidal
marsh area. These streams have slightly elevated banks which are rich
in vegetation and extend further into the brackish marsh. The marsh
is almost completely composed of smooth cordgrass with minor contributions
from other species including black mangrove |
| Brackish marsh: Found
in approximately 4704 acres of the Louisiana coastal wetlands and are characterized
as having salinity levels between 1-10 parts per thousand. Intermediate
brackish marshes contain many freshwater plants that are able to tolerate
occassional spikes of brackish water. The soil characteristics range
widely between those of the salt and fresh marshes. The marshes are
particularly affected by subsidence due to the presence of wiregrass which
require substantial sediment deposition in order to not sink. |
| Saltgrass: Found in
brackish areas on inland side of barrier islands and along the outer edges
of deltaic formations. Is present in both fresh and
salt marshes as well. Has special salt exclusion glands on leaves as
well as roots adapted to penetrate thick hard clay soils. |
|
| Salt Meadow Cordgrass: Most
dominant vegetation type in brackish region of wetlands. Can outcompete
all other species unless natural burning or grazing occurs. |
|
| Wiregrass |
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| Freshwater marsh: Covers
3,829 square kilometers. These marshes are strongly influence by
seasonal flows of the freshwater sources. They form in accreting,
sediment rich, high energy environments. Freshwater marshes are dominated
by maidencane and arrowhead and it is estimated that 70% are actually floating
mats of vegetation. Over time, woody species such as wax myrtle will
colonize these floating mats, causing them to sink and allow for recolonization
by open water plants. The portions of freshwater marsh that are not
floating are more affected by flooding and area therefore slightly less
productive. |
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Maidencane: Dominant
vegetation type in freshwater marshes and in cane zones adjacent to levees,
well adapted for living in floating mats due to thick and extensive roots
accounting for 75% of total plant biomass |
|
Cattail: Dominant vegetation
in nutrient rich portions of freshwater marsh |
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Arrowhead |
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Alligatorweed: Found
in deeper pools of fresh water |
|
Phragmites: Most
common on higher ground with fresh water, tolerant of some salt spray |
|
Waxmyrtle: Shrub
found further inland |
|
Groundsel Tree: Shrub
which prefers growing along open water |
|
Sandbar willow: Found
along high points in the upper freshwater marsh. Commonly grows on
ancient oxbows, levees and sandbars |
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Buttonbush: Commonly
found at the mouth of streams entering the marsh |
| Forested Wetlands: Found
at the landward edges of the freshwater marsh and along the main river
channels feeding the coastal wetlands. Mainly found in swamp and
bottomland forests. Much of the higher and therefore drier land was
converted to agriculture centuries ago. The swamps have anaerobic
soils, greatly limiting biodiversity. The bottomland forests are
much more diverse but are only loosely linked to the coastal wetlands through
hydrology. Levee forests are fingers of forest which extend into
the marshes along ridges of high ground formed by ancient levees. |
| Water Elm: Found in
floodplains subject to high flooding frequency, very intolerant of salt |
|
| Black Willow: obligate
floodplain species, requires poorly drained soils |
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| Water Hickory |
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| Water tupelo: Found
in deep-water swamps |
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| Baldcypress: Most common
inhabitant of deep-water swamps |
|
| Hackberry: Common tree
found in soils that are not saturated throughout the year |
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| Location |
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