The term detritus summarizes nonliving organic matter, be it of animal, plant, fungal, or microbial origin. Some authors consider detritus to include living microorganisms that colonize and nutritionally utilize particulate organic matter (POM), while others stress the presence of inorganic components in detrital pellets. However, detritus sensu strictu consists of the particulate material that is to be degraded and does not include the agents of detritus degradation nor inorganic compounds that cannot be degraded. In aquatic ecology, dissolved organic matter (DOM) is sometimes considered a significant portion of detrital matter (together with POM). Part of DOM is derived from POM through initial steps of decay, and remarkable amounts of DOM have been exuded from living organisms. Hence, DOM is, strictly speaking, not to-be-degraded dead organic matter but either a product of detritus degradation and leaching (see below, for distinction between detritus and its leachate) or, similar to fecal matter (see below), derived from living organisms rather than the result of a death event.
Herein, the focus will be on dead plant material, not including microbial or inorganic components, since this is the most significant contributor to detritus in most terrestrial and aquatic systems. This view coincides largely with what is called litter in terrestrial ecology, while POM in aquatic ecology, and wrack in marine ecology, also includes organic matter of animal origin. Thus, it is obvious that a definition of the term detritus that is commonly agreed upon can hardly be provided.
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