Meeting Abstract
P1.34 Saturday, Jan. 4 15:30 Multi-trophic impacts of shrub dominance on arctic arthropod assemblages ASMUS, AL*; GOUGH, L; BOELMAN, NT; WINGFIELD, JC; SWEET, SK; KRAUSE, JS; PEREZ, JH; CHMURA, HE; Univ. of Texas at Arlington; Univ. of Texas at Arlington; Columbia Univ.; Univ. of California, Davis; Columbia Univ.; Univ. of California, Davis; Univ. of California, Davis; Univ. of California, Davis ashley.asmus@gmail.com
In Arctic tundra, woody shrubs are increasing in size and spread as an indirect consequence of climate change. The Ecosystem Exploitation Hypothesis (EEH) predicts that increased primary producer productivity, such as a shift towards shrubbier tundra, should support greater animal biomass and potentially more trophic levels because of greater energy availability at the food chain’s base. Here, we test this hypothesis by comparing the ground-dwelling arthropod assemblages in existing shrub-dominant tundra with the assemblages in “open” tundra dominated by mosses and graminoids. We sampled arthropods with pitfall traps at four sites near Toolik Lake, Alaska. Traps were set for 10 weeks in 2012 through the summer peak of insect abundance. We captured approximately 10,000 individuals representing 80 arthropod families and a variety of trophic guilds. Overall, our results did not match the expectations of EEH. Averaged across all sites, per-trap biomass was lower in the more productive shrub tundra areas. Relative to open tundra, shrub tundra had less herbivore, predator and parasitioid biomass; however, shrub tundra did support slightly more pollinator biomass in the form of pollinating flies and bumblebees. Therefore, we suggest that aboveground plant production does not seem to be the limiting factor for the ground-dwelling arthropod assemblage. Other mechanisms, such as differences in habitat structure, plant quality or soil food webs, may be the cause of the lower biomass in shrub tundra. Regardless, a reduction in ground-dwelling arthropod biomass associated with increased shrub cover could lead to cascading negative effects for other members of the tundra food web, such as insectivorous birds and mammals.
