Okefenokee Peat ... Swamp or Bog?

Exposed Peat due to drought.

Hooded Pitcher Plant
Insects beware!

I'm not sure if I mentioned it before, but the Okefenokee swamp is not really a swamp ... though it has swamps within it. It is really a wildly diverse collection of habitats -- all variations on the peat bog. It might, in fact, be better described as a bog rather than a swamp. To the west, in the upland area there are more true swamps and less of what we normally think of as a bog. The Eastern half is very bog like. Bogs are depressions filled with peat -- usually moss or lichen and very acidic water. They tend to be fragile and diverse habitats. It is here, for example that you will find carnivorous plants as the soil is rather nutrient deficient. The peat, or collected dead plant material, has been accumulating in the Okefenokee basin for thousands of years.

Exposed peat
with a thin layer of dried muck

So why doesn't peat decay and turn to muck like we find with the plant material that accumulates in the bottom of our tidal marshes here in St. Mary's County? Well, first and obviously, peat accumulates because more organic matter is deposited than rots and so there is a net increase in organic stuff. So lets take a step back and remind ourselves of what is responsible for degrading organic stuff -- mostly bacteria (and some fungus); oxygen loving bacteria. Now here around the Chesapeake we are familiar with the problem of having too much oxygen consuming bacteria breaking down organic stuff as this is, after the excessive input of nutrient pollutants, what causes the depletion of oxygen in the water and the annual, and ever growing, summer dead-zone at the bottom of the Bay. Returning to our peat bog, we can imagine that all that plant material is a feast for the bacteria! But while feasting the bacteria consume all the oxygen, which kills the bacteria! So the available oxygen limits the amount of bacteria and the bacteria themselves limit the available oxygen! Needless to say there is not a lot of oxygen in the water of a peat bog! And, of course, the deeper you go the less oxygen there will be! (Oxygen comes from air, inputs of water and living submerged plants -- from the top!) We should note that the acidity of the water also inhibits decay, and the acidity of the water will increase the deeper we delve into the peat layer. Whew.

Peat with muck layer peeled back

So why is our marsh any different? Well, perhaps the big factor is the amount of water that enters the system. The Okefenokee is entirely rain fed so there is not a great deal of oxygen being added by incoming water. Our marshes have creeks at the back of them, bringing in fresh oxygen, and they may be subject to the tide which also increases oxygen levels. For whatever reason, the amount of dead organic material entering the marsh does not overwhelm the bacteria's ability to break it down. There is no known exact formula for why some places accumulate dead plant material and others do not.

Peat dug up a bit

So what then, exactly is peat? From the description above we can see that some areas where dead plant material is deposited do not decay rapidly, but they do decay! At least partially, until they are buried so deep that decomposition stops. While the plant material is near the surface the weaker parts of the plant (like cellulose) break down, but there is not enough time for the tougher, more resilient parts of the plant to decompose before the oxygen runs out, the acid levels build up and decay stops. So all that remains of the plant, and what accumulates over time, are the lignins or the strong structural stuff that fill the gaps in cell walls. It is what makes trees stand upright! This process of partial decay is called, not surprisingly, or creatively, "peatification".

Closeup of peat fibers ... partially decomposed plant material.