The Fallen Log

The Fallen Log (Adapted lesson of Project Learning Tree): students will gain an understanding of how decomposition takes place while closely observing microhabitats and the organisms that create a community in these places.

Materials:

• Clear containers with lids
• Paper and pencil
• Clipboard or cardboard with paper clip to take notes
• Optional: hand lenses, field guide for insects and non flowering plants

 Background for parents and students: Throughout their lives, trees collect nutrients from the environment and use those nutrients to grow. Decomposers, such as bark beetles, fungi or bacteria, will move into trees and start the decomposition process before the tree dies, often speeding up the death of the tree. 

What can you find on a dead log? 

• There will most likely be fungi, moss and lichen on your fallen log, as well as other plants (seeds that land on soft wood will often sprout and grow out of the wood). Plants and fungi break apart the wood, and moss keeps the log moist, which makes it a suitable habitat for other plants and animals to live. 
• Scavengers! Termites, ants, wood roaches will eat away and break down the log. Look for bark art left behind by bark beetles who eat away at the living layer (cambium) of the tree just under the surface of the bark and contribute to the death of a tree. 
• Predators! Look for spiders, millipedes and beetles who are feeding on the scavengers who are feeding on the rotting logs. Keep an eye out for birds and other animals who are looking to feed on the scavengers and predators!

 Doing the Activity:

1. Begin by asking students why forests aren’t piled high with fallen trees, leaves and branches. What happens to a tree after it dies? Tell students they will be examining dead logs to answer that question. Some additional questions to answer might be:

• How might the tree have died? 
• Has the tree been dead a long time or fairly short?
• What kinds of animals live on the bark? Under the bark? Inside the log? Under the log?
• Where do these animals get the food they need?
• Do any plants live on the log? How can they live without soil?

In addition to answering these (encourage students to come up with their own questions) students will be keeping track of each different kind of plant and animal they see, and where on the log they found it.

2. Explain that students should examine their log, trying their best not to disturb the living things on it as much as possible. Encourage them to look for evidence of animal activity, such as piles of sawdust, holes, tracks, webs, patterns in the wood under the bark. They can get a closer look at creatures by putting them in containers (and then return them to the spot they collected them). If they cannot identify the creature, encourage them to sketch it to identify later. Make sure they note any plants or animals they find!

3. When they are finished examining the log, have them examine areas around the log (under leaf litter, at the base of a tree, under rocks). They should note animals and plants that they found on their logs that also live in the surrounding areas. 

4. Back inside, students can identify what they could not identify in the field. Here is a great resource for insect identification 

5. Have students revisit the questions from step 1. Additional questions to consider might be

• What animals were found on the logs and in nearby areas? What do the log and other areas have in common?
• How do the animals you found on the log interact with it? (Log provides shelter, food and protection)
• Why is it important that logs decompose? (Decomposition recycles the nutrients stored in the log)
• How does the forest ecosystem benefit from a fallen log? (The log provides a habitat for plants and animals, that, in turn, are food for other creatures. As the log decomposes, its stored nutrients become available for other plants and animals).