Layers

The main layers of all forest types are the forest floor, the understory, and the canopy. The emergent layer, above the canopy, exists in tropical rainforests. Each layer has a different set of plants and animals, depending upon the availability of sunlight, moisture, and food.

• The Forest floor is covered in dead plant material such as fallen leaves and decomposing logs, which detritivores break down into new soil. The layer of decaying leaves that covers the soil is necessary for many insects to overwinter and for amphibians, birds, and other animals to shelter and forage for food. Leaf litter also keeps the soil moist, stops erosion, and protects roots against extreme heat and cold. The fungal mycelium that helps form the mycorrhizal network transmits nutrients from decaying material to trees and other plants. The forest floor supports a variety of plants, ferns, grasses, and tree seedlings, as well as animals such as ants, amphibians, spiders, and millipedes.

• Understory is made up of bushes, shrubs, and young trees that are adapted to living in the shade of the canopy.

• Canopy is formed by the mass of intertwined branches, twigs, and leaves of mature trees. The crowns of the dominant trees receive most of the sunlight. This is the most productive part of the trees, where maximum food is produced. The canopy forms a shady, protective "umbrella" over the rest of the forest.

• Emergent layer exists in a tropical rain forest and is composed of a few scattered trees that tower over the canopy.

In botany and countries like Germany and Poland, a different classification of forest vegetation is often used: tree, shrub, herb, and moss layers (see stratification (vegetation)).