Station 5: Rotten Log
Remember the decaying layer of organic material on the soil’s surface called humus? The tree that once stood above the trail at this location and then fell across it is a good example of matter decomposing to become humus, and eventually, soil. Bacteria, fungus, molds, yeast, worms and insects break down the woody material. These small organisms are important because the wood they decay is the only natural source of soil nutrients. Plants require three primary minerals for growth — nitrogen, phosphorus and potassium. Other elements such as calcium, magnesium and sulfur are also needed in smaller quantities. However, all of these minerals are of no use to the plant unless water is present. Plant roots absorb water containing the minerals so the plant can photosynthesize its food or store it for later use. Most of these minerals will be returned to the soil when the trees die and decompose. Thus, the forest cycle is continuous.