the pole in the bog
Marsh ecology
The pole's appearance tells something about marsh ecology. With time, dead plants and animals are broken down by soil bacteria. Naturally, this also applies to the old fence pole; for, it was also a plant to begin with.
Water and oxygen
Decomposing bacteria need two things in order to thrive – water and oxygen. Both of those resources are abundant just above the ground surface – oxygen in the air, and the pole absorbs water from the marsh. Higher up, the pole is dry, and the section below ground is in an oxygen-free environment. Why is there no oxygen?
No oxygen
The water in a marsh seldom comes in contact with the air and its oxygen, and is therefore poorly oxygenated. Also, the marsh contains great quantities of dead plants that are broken down by bacteria which get their oxygen from the water. Before everything is decomposed, all the oxygen has been used up.
Varying speed
The process of decay goes slowly in the relatively dry environment high up on the pole and in the oxygen-free soil beneath the surface. Decomposition proceeds most rapidly near the surface of the ground. This is what you see on the pole.
