 Ah, fall is here! One of the signs is the abundant amount of yellow leaves on the ground, but soon the seasons will change and the snow will cover all the leaves. But when spring time comes, what will happen to all these leaves? Decomposition is the process of breaking organic substances down into simpler forms of matter. First, the leaves fall to the ground, then they soak up water and soluble compounds are released. Along comes an insect or worm to start breaking them into smaller pieces. Now that they are in very small pieces, the microorganisms can begin their work. The most common microorganisms to do this are bacteria and fungi. They secrete chemicals which further breaks down the leaves. The partially digested plant material that is left is called humus. Humus is a major source of nutrition for plants. The rate of decomposition is influenced by the availability of oxygen, moisture, access by decomposers, the material being broken down, and the temperature. Warmer is faster. Decomposition can be accelerated in a compost pile by the buildup of heat and moisture and turning to increase oxygen availability. Decomposition is a vital process without which we would be overrun by mountains of dead biomass. From the University of Wyoming Extension, I'm Mae Smith, Exploring the Nature of Wyoming.