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Theforest floor, also calleddetritus orduff, is the part of aforest ecosystem that mediates between the living, aboveground portion of theforest and the mineralsoil, principally composed of dead and decaying plant matter such as rottingwood and shedleaves.[1] In some countries, like Canada, forest floor refers to L, F and H organichorizons[jargon].[2] It hosts a wide variety ofdecomposers[3] andpredators, includinginvertebrates,fungi,algae,bacteria, andarchaea.
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 thebiogeochemical 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 throughlitterfall, 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 asarthropods andfungi, 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 inforest fires.[citation needed]
The amount of material in the forest floor depends on the balance between inputs from litter production and outputs from decomposition, and amounts also reflect the site's disturbance history. Both litter production and decomposition are functions of the site (e.g., wet versus dry; cold versus warm; nutrient rich versus nutrient poor) and the vegetation that occupies the site (e.g.,conifer versusbroadleaf). A site's forest floor is determined by its areal weight, depth, and nutrient content. Typically, forest floors are heaviest and deepest inboreal forests andmountain forests where decomposition rates are slow. In contrast, the lightest and thinnest forest floors usually occur intropical forests where decomposition rates are rapid, except on white sands where nutrients could not be supplied frommineral weathering.[citation needed]
The organic layer is divided into three layers: on the surface is theleaf litter formed by undecomposed vegetable matter; underneath ishumus which is the product of decomposed vegetable matter. Between litter and humus is a partially decomposed layer of organic matter ("F: fragmented organic materials").[10][11] Some specialists consider this zone to be equivalent to thesoil horizon (O) whereas for others, this only includes the humus and the intermediate layer, excluding the litter. Woodland plants that inhabit this zone often have bulbs or rhizomes and include ferns such asbracken,monocots such as bluebells anddog's mercury.[citation needed]
In tropical rainforests, the soil itself is often very poor, in contrast to the soils of temperate forests which store nutrients in soil. The lush vegetation is made possible by the abundance and rapid action oftermites,millipedes and other organisms, which break down organic matter and promptly consign it to themycorrhizal network.[12] Therefore, the leaf litter layer oftropical forests may be considerably less apparent, or virtually absent at certain times of the year. With up to three defined canopy layers above, relatively low levels of sunlight (as little as 2%) reach here.[13] Examples of the wide range of plants adapted to this zone include:spike mosses,gingers and the parasiticRafflesia spp.[citation needed]
Media related toplant litter at Wikimedia Commons Media related toforest floors at Wikimedia Commons