Nature Bulletin No. 441-A   January 22, 1972
Forest Preserve District of Cook County
George W. Dunne, President
Roland F. Eisenbeis, Supt. of Conservation

****:ROTTING LOGS

Trees are like people. They die from diseases, infections, injuries, 
burns, drowning, malnutrition, and sometimes just plain old age. 
Walking through the woods we see, here and there, dead or dying trees 
of various kinds. For example: a big white oak, with its bark ripped 
from crown to root, was literally cooked by a bolt of lightning during a 
summer thunderstorm. In a grove of black oaks, many are dying 
lingering deaths from infected wounds started years ago when an 
autumn fire swept through the fallen leaves and scorched the living 
wood. In a dense forest there are many that have lost the battle for space 
and sunlight. In some places we see trees that are slowly starving 
because dashing rains have carried away the fertile topsoil and the 
trampling feet of picnickers have injured the shallow roots that bring 
them food.

In our forest preserve picnic areas, for public safety, we remove dead 
trees but elsewhere we let them stand until they fall and then rot where 
they lie. A lot of people think that is both untidy and wasteful but there 
is an important reason for it. In order to restore or maintain a healthy 
natural woodland and all of the wheels within wheels of the living 
machinery that makes it tick, those slowly decaying trunks, branches 
and twigs are vitally necessary. It would be a strange forest without 
them.

A forest is more than trees. The trees are the framework but around 
them is woven an unbelievable complex fabric of life: squirrels, mice, 
birds, bees, beetles, worms, wildflowers, weeds, mushrooms and many, 
many more. Over a period of years a slowly enlarging hole in a standing 
dead snag, for instance, may be occupied in turn by a fungus, a boring 
beetle, a colony of carpenter ants, a woodpecker, a deer mouse, a 
squirrel, a screech owl, and a raccoon. The dead roots, the loosening 
bark and the softening trunk also shelter or feed a host of other wood 
colonists. The roots gradually weaken until one day, in a gust of wind, 
the snag crashes to the ground where the final act of the drama takes 
place.

Some fallen trees rot much more rapidly than others, depending upon 
the kind of tree and whether or not it lies in contact with damp soil. 
Bacteria and the root-like threads of fungi -- whose fruits are 
mushrooms -- spread inward through pores and crevices in the dead 
wood, eating away some of it and leaving the remainder soft. The 
mushroom growths on the outside of the rotting log may include several 
sizes, shapes and colors: bracket types, puffballs, parasols, and some 
resembling a turkey gobbler's tail, oyster shells, or crusts.

There is little hint of the wealth of small animal life within until you 
pull off a big piece of loose bark. Ants, centipedes, millipedes, daddy-
long-legs and beetles scurry away. On the exposed wood are artistic 
patterns made by the engraver beetle. A fiery red mite may creep under 
a shred of bark. Soon there is left no visible sign of life except tunnels 
into the softened wood and perhaps a silk-covered ball of spider eggs 
hidden in a crack.

Now roll the log over. On the moist underside there are likely to be sow 
bugs, slugs, snails, earthworms, spiders, crickets, firefly larvae and 
various beetles. There may be a salamander or two, a toad, a harmless 
snake, and a mouse's nest with her store of seeds. At this season all of 
these creatures are in their winter sleep, so be sure to roll the log back 
in place. Living and dying, generation after generation of them convert 
that wood back into soil food and humus which a healthy forest must 
have .

There is drama and treasure in a rotting log.