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is used as a general term for all that was recently living together with excreta (see Chapter 2). The organic matter derived from tissues in the litter is increasingly digested by repeated cycles of ingestion and excretion. Species participate in the ingestion of food, its partial digestion and absorption, and excretion of the remaining portion. Therefore, repeated cycles of biological processing and chemical modification of organic matter have two effects. One causes an accumulation of increasingly indigestible (or recalcitrant) organic matter. The other supplies a steady source of soluble nutrients into the soil solution. The end result of decomposition trophic interactions is the return of nutrients into primary production food webs, in the form of soil solutes, carbon dioxide and other gases (Figs 2.1 and 4.1).

Primary production-driven consumers and their parasites

Primary production-driven consumers and their parasites

Litter Decomposition Nutrients

Litter decomposition-driven saprotrophs and their parasites

Fig. 4.1. Flow of nutrients between primary production and saprophytic species. The diagram does not indicate the biomass and amount of flow, but shows the direction of flow between living and decomposing biomass. Numbered arrows indicate (1) uptake of nutrients from the soil solution by roots and rhizoids; (2) uptake of nutrients by mycorrhizae; (3) litter from plant-derived tissues; (4) plant tissue digestion by symbionts of consumers of primary producers; (5) consumption of primary producers; (6) litter from consumers in the primary production subsystem; (7) litter from saprotrophs; and (8) consumption of saprotrophs by consumers in the primary production subsystem.

Litter decomposition-driven saprotrophs and their parasites o u> y

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