Friday, December 2, 2011

Louisiana Wetlands and the Mississippi River Delta Part 1

A Louisiana bayou in the Mississippi River Delta.  
Louisiana boasts an amazing 40 to 45 percent of the continental United States wetlands.  Flying into, and driving through Southern Louisiana gives you a good sense of the vastness of these wetlands, miles and miles of unbroken soggy earth everywhere.  Water is literally everywhere, there is of course lots of open water, and where there isn't open water there are sopping wet grassy marshes, and where there aren't mashes their are soaked forests.  The air is always full of humidity with a faint marshy smell, no matter where you are at.  I have visited many wetlands in my life, but none compare to the expansiveness and diversity of these subtropical wetlands.

A part from the sopping wet nature of southern Louisiana, the next most obvious feature is the perfectly flat nature of this landscape.  This soaked flat landscape is a result of the Mississippi River reaching the Gulf of Mexico and depositing massive amounts of water and sediment as the river slows before dumping into the ocean.  The Mississippi begins as a small clear stream at Lake Itasca in Northern Minnesota, which I have personally walked across in only a few short steps that only went up to my knees.  Growing up, I also fished the Mississippi River in Iowa where it is a mighty and muddy river.  Flowing southward, the river continues to grow in volume and accumulate more muddy sediments making it "The Big Muddy."  All this water and mud however has to end up somewhere and is deposited in a delta entering the Gulf of Mexico in southern Louisiana.  This deposition and delta forming process has been taking place for thousands of years since the end of the last ice age.  The entirety of Southern Louisiana was at one time deposited by the Mississippi, and today, over one mile of sediment covers the underlying bedrock.
Oak trees draped with Spanish Moss along a higher, drier portion on a bayou.
Along the Mississippi and other distributary rivers flowing out of it, heavier sandy sediments are deposited along the bank.  These sediments form a sort of natural levee elevated above the rest of the alluvial plain.  On these natural levees many species of oaks are commonly found including the Southern Live Oak, Water Oak, and Swamp Laurel Oak.  These Oaks can only tolerate temporary flooding and need to be on dry land adjacent to lots of water, such as next to a river or swamp.  A short distance from the river, the natural levee slopes slowly down, away from the river.  As the slope moves downward, away from the river, the ground becomes increasingly wet.  Maples and Ash grow on this wetter back-slope along with some oaks.  Lower on the back-slope the ground becomes increasingly saturated, often with standing water, here Baldcypress and Water Tupelo grow.  These areas are still high enough on the slope so that they are not flooded for extended periods of time.  Cypress trees can grow for over 1000 years on these sites and grow large "buttress" roots around the base of their stump in order to stabilize themselves for these long periods of time in these soggy loose soils.  All of these trees are draped with often thick clumps of Spanish Moss.  This moss, is technically not a moss at all but rather more closely related to a pineapple, very odd considering they look nothing alike.  These draperies of Spanish Moss are normally tan colored, except for after rainfall when they turn green.  Hanging from trees and blowing in the wind the moss gives the narrow bayous a romantic southern feel, as they decorate the majestic oaks and cypress trees.
Baldcypress trees found in wetter portions of the wetland then the oaks.  
A floating marsh wetland characterized by grasses, sedges, and rushes.  These types of marshes are important locations for alligator hibernation.

Away from the natural levee and closer to the mouth of the river where the water is always flooded, floating marshlands exist which are dominated by grasses, rushes, sedges, and cattails.  Historically, these floating marshes were far more common and widespread.  As they were settled, channels were dug through these marshes and the sediments piled adjacent to the channel.  These new channels formed what are known today as bayous with the adjacent piles of sediments forming vegetation similar to the natural levees along rivers.  These marshes and bayous can have brackish water (slightly salty) or freshwater and are filled with an abundance of life.  Brackish waters have crabs, while crayfish are found in fresh, both of which are trapped for the great seafood the area is known for.  Bass, crappies, drum, gar, and catfish are in abundance in these areas.  A guide told me there are so many fish in these wetlands that if you don't catch any fish, you don't tell anyone.  In other words, there are always fish to be caught, and to not catch any is not typical, and embarrassing.  Birds also fill these areas including waterfowl of all types, herons, and ibis.

This concludes part one of the Louisiana Wetlands.  In our next entry we will cover the famous alligator of these wetlands as well as some of the ecological issues they face today.  

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