A decaying log lying on the floor of the forest appears lifeless and useless to the casual observer. Nothing could be further from the truth, however, as the decomposing wood harbors thousands of living organisms within and beneath it, in their own unique ecological community.
Existing in conjunction with the log and in consort with each other, living and dying, generation after generation, they recycle the log back into the organic elements that a forest must have. This recycling process also produces rich humus, which not only helps the soil to retain its moisture but also aids in making minerals more readily usable as plant nutrients.
Finally, after many years, the decomposition process is complete, and nothing is left of the original tree except crumbling punk riddled with the hyphae, or roots, of molds and mushrooms. Frugal Mother Nature has reclaimed the elements of life she originally loaned to the living tree.
Some of the organisms one might find associated with a decaying log in the Rock River Valley are as follow: bacteria, slime molds, fungi, lichens, mosses, ferns, protozoa, nematodes, earthworms, sow bugs, centipedes, millipedes, pseudoscorpions, wood roaches, termites, boring beetles, beetle larvae, springtails, fly larvae, and various amphibians and reptiles.
Each of the organisms attacks the rotting log in its own way. The termite, for example, ingests the deteriorating wood that is largely composed of the complex carbohydrate cellulose. Unfortunately for the termite, it has a difficult time digesting cellulose and would probably starve to death if it did not have symbiotic protozoans nestled snugly in its gut. These minute animals can break down the cellulose to usable sugars that are shared with its termite host. This sort of association is a neat biological arrangement called mutualism, where the insect provides the protozoan with a warm, moist, home and plenty of food, and the protozoan provides the termite with usable carbohydrate.
Boring beetles and wood roaches also rely on the good services of the mutualistic protozoans to digest cellulose to sugar, but the earthworm and others are equipped with cellulose-digesting enzymes and need no digestive assistance. As the worm ingests bits of wood, a muscular gizzard grinds them into tiny particles to ftcilitate digestion.
Bacteria and the other lower forms of life found in a rotting log have evolved certain special processes that enable them to exploit their environment by utilizing cellulose and the waste products of animals to obtain food to be converted into energy. These minute and primitive organisms form the first link in the food chain of the rotting logs ecology and are eaten by larger creatures termed predators, which in turn, are eaten by larger predators. The flow of energy, which originally came from the sun and was trapped and stored by the living tree, is then complete throughout the members of the rotten log community.
Many species of snakes set up housekeeping under downed logs, as do certain types of amphibians, especially salamanders.
While they stand, dead and decaying trees furnish homes for many mammals and birds including bats, squirrels, opossums, raccoons, wrens, bluebirds, woodpeckers, wood ducks, owls, and a host of other vertebrate forms of life. When the dead tree falls to the ground and is in the initial stages of decomposition, it continues to furnish harborage for many species. A dead and decaying tree is far from lifeless.
Jonathan Swift accurately described what is going on in a rotting log when he wrote:
So, naturalist see, a flea
Hath smaller fleas that on him prey
And these have smaller fleas still to bite them,
And so proceed ad infinitum.
The next time you pass a rotting log in the wood, be aware that there is a flea circus occuring within it.
Dr. Robert Hedeen is a former resident of Marylands eastern shore and resided in the Chicago area from 1960-1971. He is a retired professor emeritus of biological sciences in the University of Maryland system. He has published more than 30 scientific papers, has written numerous magazine articles, and is the author of two books on the natural history of the Chesapeake Bay.