Forest floor

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The forest floor, also called detritus or duff, is the part of a forest ecosystem that mediates between the living, aboveground portion of the forest and the mineral soil, principally composed of dead and decaying plant matter such as rotting wood and shed leaves.^[1] In some countries, like Canada, forest floor refers to L, F and H organic horizons.^[2] It hosts a wide variety of decomposers^[3] and predators, including invertebrates, fungi, algae, bacteria, and archaea.

The forest floor serves as a bridge between the above ground living vegetation and the soil, and thus is a crucial component in nutrient transfer through the biogeochemical cycle. Leaf litter and other plant litter transmits nutrients from plants to the soil.^[4] The plant litter of the forest floor (or L horizon) prevents erosion, conserves moisture, and provides nutrients to the entire ecosystem.^[5] The F horizon consists of plant material in which decomposition is apparent, but the origins of plant residues are still distinguishable.^[2] The H horizon consists of well-decomposed plant material so that plant residues are not recognizable, with the exception of some roots or wood.^[2]

The nature of the distinction between organisms "in" the soil and components "of" the soil is disputed, with some questioning whether such a distinction exists at all.^[6] The majority of carbon storage and biomass production in forests occurs below ground.^[7] Despite this, conservation policy and scientific study tends to neglect the below-ground portion of the forest ecosystem.^[8] As a crucial part of soil and the below-ground ecosystem,^[9] the forest floor profoundly impacts the entire forest.

Much of the energy and carbon fixed by forests is periodically added to the forest floor through litterfall, and a substantial portion of the nutrient requirements of forest ecosystems is supplied by decomposition of organic matter in the forest floor and soil surface. Decomposers, such as arthropods and fungi, are necessary for the transformation of dead organic matter to usable nutrients. The sustained productivity of forests is closely linked with the decomposition of shed plant parts, particularly the nutrient-rich foliage. The forest floor is also an important fuel source in forest fires.