title: Parallel ecological networks in ecosystems.
abstract: In ecosystems, species interact with other species directly and through abiotic factors in multiple ways, often forming complex networks of various types of ecological interaction. Out of this suite of interactions, predator-prey interactions have received most attention. The resulting food webs, however, will always operate simultaneously with networks based on other types of ecological interaction, such as through the activities of ecosystem engineers or mutualistic interactions. Little is known about how to classify, organize and quantify these other ecological networks and their mutual interplay. The aim of this paper is to provide new and testable ideas on how to understand and model ecosystems in which many different types of ecological interaction operate simultaneously. We approach this problem by first identifying six main types of interaction that operate within ecosystems, of which food web interactions are one. Then, we propose that food webs are structured among two main axes of organization: a vertical (classic) axis representing trophic position and a new horizontal 'ecological stoichiometry' axis representing decreasing palatability of plant parts and detritus for herbivores and detrivores and slower turnover times. The usefulness of these new ideas is then explored with three very different ecosystems as test cases: temperate intertidal mudflats; temperate short grass prairie; and tropical savannah.
authors.affiliation: Centre for Ecological and Evolutionary Studies, University of Groningen, PO Box 14, 9750 AA Haren, The Netherlands. h.olff@rug.nl
authors.forename: Han
authors.initials: H
authors.lastname: Olff
authors.forename: David
authors.initials: D
authors.lastname: Alonso
authors.forename: Matty P
authors.initials: MP
authors.lastname: Berg
authors.forename: B Klemens
authors.initials: BK
authors.lastname: Eriksson
authors.forename: Michel
authors.initials: M
authors.lastname: Loreau
authors.forename: Theunis
authors.initials: T
authors.lastname: Piersma
authors.forename: Neil
authors.initials: N
authors.lastname: Rooney
mesh_terms: D000818:Animals; D003120:Colorado; D003718:Denmark; D017753:Ecosystem; D004777:Environment; D020387:Food Chain; D008386:Marine Biology; D008954:Models, Biological; D006109:Poaceae; D011235:Predatory Behavior; D013019:South Africa