When you come upon a rotting log in the woods or along a woodland trail, this may prove to be an interesting encounter with diverse life forms that either gobble the decaying wood or benefit from other creatures that do so. Although these tree trunks themselves are lifeless, they are the main part of a mini eco-system that supports many living things. Mushrooms and other fungi, lichens, insects and other arthropods, slime molds, salamanders, springtails, birds, and mosses are some of the organisms that can be found inside, on, or under these logs.
One thing that decaying wood releases is carbon, which is part of the natural process that stabilizes climates in the long-term. Forests can absorb carbon, and as trees die and decay over time, the carbon released goes back into the atmosphere. According to German ecologist Sebastian Seibold, “trees both absorb carbon during photosynthesis and release it when they respire, and together with deadwood decomposition, these carbon-inhaling and carbon -exhaling processes help to keep the composition of the atmosphere stable.”
This year, dead logs have been especially full of certain life forms because of the occurrence of rainfall in the summer and fall that kept the wood wet. Especially evident have been certain fungi and slime molds.
Wasp nest, tapioca, red raspberry, wolf’s milk and white coral slime molds are easiest to see when their fruiting bodies are present. A good hand lens will help you identify these tiny organisms. Red raspberry slime, for instance, may appear like a smear of red jam on a log where bark is missing when the fruiting bodies appear. The well-named pretzel slime mold is found on moist, punky wood under rotting bark.
Fungi that feed off of dead wood help to decompose it over time. Turkey tail and false turkey tail fungi often occur in large groups, and their size makes them easy to find. Blue stain cup fungi are so small, you need to look for the dead wood they have caused to stain blue which indicates their presence. Jelly disks like the Ascocoryne sarcoides can be found from fall to winter on dead wood in forests. Bear’s head tooth fungi looks like a mass white icicles hanging down from decaying tree trunks and logs. The violet crust fungi, Phlebiopsis crassa, often covers sections of dead logs where bark is still intact.
Insects that feed on dead and decaying logs may be better found by pulling off loose bark. Sometimes pillbugs and larvae of wood eating beetles may be found by doing so. Handsome fungus beetles will feed on crust fungi on the outers ends of logs. Research has shown that up to one third of insects found in forests and woodlands benefit from deadwood, either by feeding on it or by feeding on the insects that do. In turn, these insects become food for birds that know where to look for them. Pileated woodpeckers are a good example of a bird that is well adapted to tapping into trees and logs that insects are living inside.
Rotting logs and stumps are a good springboard for plants like ferns and certain tree saplings to grow on. A good example is the stilt-rooting yellow birch, whose seeds will germinate on stumps. The seedling sends roots over the sides of the stump where they penetrate the ground. Over time, the stump (or log) decays, and the tree looks like it is on stilts.
Look for slugs and snails feeding on both moss and algae on logs. They will also feed on all types of mushrooms, both on the caps and the stalks, so check any fleshy mushrooms you find on or near logs. Springtails can be found on jelly fungi like witch’s butter even in the winter. This fungus is brilliant yellow and is easy to spot on dead wood.
Turning over a dead branch or log that remains intact may reveal a salamander or two any time of year. I have found a red- backed and a spotted salamander under the same log this week. The microclimate under the log provides moisture and food like worms and other arthropods and also protection for these amphibians. Be careful when rolling the log back to avoid injuring these creatures.
As a final note, there are always surprises when exploring the natural environment, for instance, when overturning a section of decaying log that was hollow, it split open to reveal a mourning cloak butterfly in diapause in this excellent overwintering spot. I put it back carefully, as this butterfly is one of several species that will overwinter, and it will sometimes be seen flying about the woods on warm winter days.
