November 22, 2010

The Lower Mississippi Valley Region - Ecological Perspective

The flat water-logged land that is the Lower Mississippi Valley is an amazing landscape of life's resilience. Everywhere you look, life is creeping, growing, running, or flying by. And, this is in the cooler months of Autumn. I can only imagine how it is when it is in the grip of the heat and humidity of summer. But, this landscape has the perfect combination of three critical ingredients; heat, moisture, and nutrient-rich soils. Where lush plant life grows, animals will follow.

Flocks of white pelicans converge on an oxbow lake of the Arkansas River
But, these key ingrediants are also what brought people to the region. In conditions my pampered body would consider absolutely miserable, people toiled for centuries to turn swamps and jungles into farmland. Forests were cleared, swamps drained, soils plowed, rivers tamed, and DDT sprayed. How people managed to do this work in the 1700's, under the threat of malaria, snakes, heat stroke, alligators, and spiders I will never truly know or understand.

Over 80% of the original bottomland forests and swamps along the lower Arkansas and Mississippi Rivers have been cleared for agriculture. Once cotton was king ... and it is still grown quite a bit. But, soybeans, rice, corn, tobacco, and other crops are still grown in a landscape where growing conditions last 8-9 months per year and irrigation is basically unnecessary because of the heavy summer rains and high water tables.

Maps showing the loss of bottomland forests and wetlands in the region
But, it has taken its toll on the forests and wildlife. While life is still quite plentiful, where there were once flocks of billions of passenger pigeons and Carolina parakeets, there are now none. Cypress swamps, once so prevalent, are now just narrow strips of green water and huge buttressed trunks you pass on the highways between the extensive fields. Because of the constant threat of insects, fungus, and weeds, this landscape is heavily sprayed with insecticides, fungicides, and herbicides. Organic farming is non-existant here according to a local fruit stand owner we talked to simply because it is impossible.

This was just one section of the perhaps 100's of thousands of blackbirds we saw in this field
But, although we have yet to stop specifically at a cypress swamp or birding area (it's on the agenda), I have rarely seen such a proliferation of life on the horizon or on the roads. Flocks of birds in the thousands soar overhead. Snow geese, herons, egrets, woodpeckers, bluebirds, various hawks and falcons, and blackbirds are constant companions on the highway. And, don't even get me started on the number of roadkill and the accompanying flocks of vultures! At night, we are constantly coaxed to sleep with the hoots of barred, screech, and great horned owls.

Don't worry, THIS copperhead was in a nature center
But, where the land remains relatively intact or where the fields have gone fallow (actually quite common), the forests grow back at amazing speed. We did an interpretive trail where they said the cotton field was abandoned 60 years ago and it was very enlightening...

In upland sites of sandy well-drained soils, such as this former cotton field, the first trees to invade are loblolly pines. These trees are about 60 years old and are slowly being replaced by more shade-tolerant hardwood species.

A magnolia rising up into the stand of hardwoods
Here, in the same stand , hardwoods like southern red oak, sweet gum, tulip trees, magnolias, and even some beech are coming up and replacing the pines. Many of the pines are being ripped apart by the vines that cover their trunks. When those vines break off in windstorms, they tear the bark right off the pines as well and the internal rot is visible. In a humid climate like this, wood does not last long against rot.

Everything in these forests is covered in huge vines of various species.
In this case, these are large grape vines.
Along the sandy streamsides, where disturbance is common, but the soils drain well, forests of cottonwood, sycamores, hackberry, sugarberry, and water oaks dominate. The understory is thick with native cane grasses, vines, and various shrubs.

Native cane grasses along the sandy riparian bottoms
There is definitely a reason we came to this region in November and not July. I serious do not understand why anyone would want to live down here in the summer. This is especially true of the era before the air conditioner. But, really, that explains why states like Texas, Florida, Georgia, and the Carolinas did not see their populations explode until after World War II. As for Arkansas, Mississippi, and Alabama? No such population explosion ever occurred...Any guesses why? That's the subject for another post to come!

This is definitely the biggest spider on a web I have ever seen!
But, my personal preferences and biases aside, I can really appreciate this place as an ecologist and educator. The only thing that makes this place "sub-tropical" rather than tropical are the cool to occassionally cold winters. But, when the heat and humidity return in May (sometimes April), the life will emerge from its torpor and the sounds of crickets, cicadas, and the constant buzzing of mosquitoes will fill the air.

Stand of Water Oaks
We've caught glimpses of the bottomland forests and swamps along the way, but have yet to find the right place to actually stop and explore them. That is a priority and there will be a forth-coming post about the water-logged soils that do not drain well and what happens when you have lots of water in and on the land.

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