Park Naturalist, Long Branch Nature Center
It happens every autumn, the leaves turn color and then drop to the ground. So why don’t the leaves pile up to the branches, along with all the twigs, branch, and logs that fall throughout the year? A vast army of organisms recycles all that organic material back into the soil, releasing nutrients that support new plant growth. This critical task goes on virtually unseen by the most humans.
Fungi and bacteria do the heavy lifting in this world, decomposing of 80 – 90% of forest detritus. But other than mushrooms, the fruiting bodies of fungi, they are mostly visible only under high magnification. More visible, if you know how to see them, are a wide variety of animals that also play an important role in breaking down all that stuff that falls from the trees. Though some of them are microscopic or nearly so, others are visible with the naked eye or with a magnifier.
Collectively, these animals are often called litter critters, since they dwell in the leaf litter covering the forest floor. Perhaps the best know litter critters are earthworms, which emerge from their burrows at night to feed on dead leaves. Another familiar litter critter is the roly-poly or pill bug. Roly-polies are crustacean rather than an insects and breathe through gills. To keep their gills moist, roly-polies usually stay in the moist microclimate under leaves, logs, or other cover.
Other readily visible litter critters include slugs, snails, millipedes, adult beetles, beetle grubs, and fly larvae. Much smaller, and usually found under logs, termites play a huge role in decomposing fallen branches and logs. This is because they are among the few animals capable of digesting cellulose, the major component of wood. Smaller still are various springtails (of the order Collembola) and mites. These are best appreciated through a hand lens, although you might spot a bright red velvet mite walking across the dead leaves.
Not all litter critters eat leaf litter. Spiders, centipedes, ground beetles and other tiny predators search the forest floor for other litter critters. And the danger isn’t limited to predatory invertebrates. Salamanders, relative giants in this world, feed on predators and detritivores alike. It’s a real jungle down there!
You can get a glimpse of this world by sifting a few handfuls of leaf litter through some hardware cloth onto a white sheet. Watch for tiny creatures moving a few moments after you stop sifting. A small jar or bug box will help you detain some of these critters for a closer look. But be sure to them back in the leaf litter to continue their important work. They might be tiny, but they are essential to the health of the forest.