Cycles in food webs can be divided into two main classes: feeding cycles and nonfeeding cycles. The former involve species and their feeding relations (e.g., species A eats species B; species B eats species A); cannibalism is a simple kind of feeding cycle. The latter are typical of food webs that comprise detritus compartments and nutrient pools: organic matter is recycled in the system via mineralization, creating a huge number of detritus-mediated cycles.
Feeding cycles are rare in published food webs. This is mainly due to the fact that the resolution of food webs is usually at the species/group of species level. The number of feeding cycles becomes more significant when age-structured populations are considered, especially in aquatic food webs. Nonfeeding cycles, on the other hand, are extremely abundant in published networks, being several billion cycles for highly resolved ecosystem models.
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