Forest Floor

Two main types of forests grow in the regions between the tropics and the poles, deciduous forest and coniferous forest.  A majority of energy from sunlight is captured by the canopy vegetation, with little leftover to reach the forest floor.  And yet, the lowest level of the forest has an abundance of food and organisms.

Deciduous species are mainly hardwoods including oak, birch, maple, ash, beech, and hickory.  These trees have leaves that are broad and flat, designed to catch sunlight.  Conifer forests are made up mostly of softwood tree species from the pine and fir families.  Most conifers have leaves that are long, thin, and needle-like, a compact form of leaf that is often waxy and designed to withstand the rigors of an environment that is cold and dry for long periods.

Chlorophyll is a chemical that is synthesized by plants and gives leaves and needles their characteristic green color.  Plants use chlorophyll to absorb energy from sunlight and use that energy to power the process of photosynthesis which creates carbohydrates, providing food for the rest of the plant.  Senescence, the process that occurs when a plant stops making chlorophyll, happens as seasons change and day length shortens while temperatures fall.  As chlorophyll is removed, leaves and needles lose their green hues and show their underlying colors of browns, reds, and oranges even as they die and fall to the forest floor.

^{Black beetle on forest floor by Undefined, Getty Images; Forest floor fungi cluster in Autumn woods by Vladimir Srajber, Pexels; Springtail on fallen log by Henrik L, Getty Images; Lush moss covering the forest floor by Doina Gherban}

Fallen leaves create a thick layer of litter, broken down by a rich variety of decomposers including mosses, fungi, insects, and other invertebrates.  Decaying vegetation releases nutrients back into the soil to be used once more as food for other forest plants.  The annual leaf fall adds an estimated 2,600 pounds of vegetation per acre back into forest habitats worldwide.

In deciduous forests, all of the leaves typically fall in late autumn opening up the forest floor to sunlight in early spring.  A group of plants known as spring ephemerals take advantage of this sunlight to quickly flower, bloom, and reproduce before leaves re-appear and shade once more rules the forest floor.  In conifer forests, where shade is ever-present, flora is restricted to shade-loving species such as ferns and fungi.  In addition, fir and pine tree needles are high in acid content and their leaf litter is only broken down by a relatively few fungi species over long periods of time.

All forest floors are rich with many organisms present throughout the year.  Invertebrates including insects, fungi, and small mammals spend their entire lives living in the leaf litter.  Detritus from leaf fall provides food and nutrients throughout the year to the plants and other organisms living in these wonderful habitats.  As you walk the forests, no matter what the season, think about all of the life going on around you each day on the rich woodland floor.