Interactive effects of changes in atmospheric CO2, temperature and precipitation on microarthropod communities in an old field ecosystem

Background/Question/Methods Under global climate change, if rising atmospheric temperatures alter plant and soil microarthropod communities, the effects may be moderated or exacerbated by rising atmospheric [CO₂] and changes in precipitation regimes.  We used an ongoing (5 year), multifactor (ambient or elevated carbon dioxide concentrations [CO₂], ambient or elevated temperature, and moist or dry soil) experiment in a constructed old field plant community (including C3 and C4 grasses, forbs, and legumes) to better understand if and how interactions among global change factors and subsequent changes in plant performance alter soil microarthropod community structure.  Soil cores (3 replications per plot, 0 – 15 cm, 2cm diameter) were collected from plots arranged in a randomized complete split design (12 chambers, 4meter diameter, each split into wet and dry treatments for a total of 24 plots) located at Oak Ridge National Laboratory in eastern Tennessee at the end of the growing season in 2007 and in June of 2008.  In July of 2008, plant and root biomass and surface litter depth data were collected as a proxy for above and belowground primary productivity.  Microarthropods were extracted from soil cores in modified high-gradient Tullgren funnels, and identified to species and morphospecies.    
Results/Conclusions Our data indicate that drought decreases microarthropod abundance and richness, ultimately altering microarthropod composition (Bray-Curtis, ANOSIM), but changes in temperature and atmospheric [CO₂] have little to no impact on microarthropod communities.  Results indicate that local alterations in precipitation regimes may lead to litter and root productivity-mediated changes in belowground microarthropod community attributes with implications for theory concerning and management of above and belowground interactions, ecosystem cascades, and stability of ecosystem processes such as nutrient cycling and litter decomposition in old fields.