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dc.contributor.authorGruner, Daniel
dc.date.accessioned2007-08-30
dc.date.available2007-08-30
dc.date.issued2004
dc.identifier.citationGruner, D. S. 2004. Attenuation of top-down and bottom-up forces in a complex terrestrial community. Ecology 85:3010-3022en
dc.identifier.urihttp://hdl.handle.net/1903/7108
dc.description.abstractCarnivore (top-down) and resource (bottom-up) influences in food webs are strong and pervasive, but few studies have investigated their interactive effects in species-rich terrestrial ecosystems. This study focused on arthropods associated with the dominant tree species, Metrosideros polymorpha (Myrtaceae), in Hawaiian forests. Severe soil nutrient limitation on a 120-yr-old lava flow was removed by fertilization and combined with bird predator exclusion cages in a randomized block design. Arthropod densities were measured from clipped foliage at the outset and conclusion of a 33-mo experiment, and their biomass was estimated using regression equations. Metrosideros foliar nitrogen, tree growth, and biomass increased directly in response to fertilization but did not change with bird exclusion. Fertilization increased detritivore densities but not biomass, and both density and biomass of herbivores, while bird exclusion increased both density and biomass of carnivores. Fertilization also increased spider density and biomass, but bird exclusion increased spider numbers (15 species) only in high resource plots. Overall, trophic level biomass responses were less pronounced than density because smaller bodied individuals responded more to enrichment. Bottom-up factors controlled basal trophic levels, and detritivores comprised the largest fraction of arthropod density and biomass. Conversely, top-down impacts were apparent but variable, limited to higher order consumers, and did not cascade to the level of primary producers. These experimental results were consistent with the view that complex forest ecosystems are structured on a bottom-up template.en
dc.format.extent394627 bytes
dc.format.mimetypeapplication/pdf
dc.language.isoen_USen
dc.publisherEcologyen
dc.subjectArthropodaen
dc.subjectbottom-up and top-down processesen
dc.subjectfertilizationen
dc.subjectHawaiian Islandsen
dc.subjectinsectivorous birdsen
dc.subjectMetrosideros polymorphaen
dc.subjectspidersen
dc.subjectpredator exclusionen
dc.subjectterrestrial food weben
dc.subjecttropical island montane foresten
dc.titleAttenuation of top-down and bottom-up forces in a complex terrestrial communityen
dc.typeArticleen
dc.relation.isAvailableAtDigital Repository at the University of Marylanden_us
dc.relation.isAvailableAtEntomologyen_us
dc.relation.isAvailableAtCollege of Chemical & Life Sciencesen_us
dc.relation.isAvailableAtUniversity of Maryland (College Park, MD)en_us


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