Non-litter effects of elevated CO2 on forest floor microarthropod abundances

The arthropod assemblages of the litter and soil play significant roles in decomposition and nutrient cycling. At the FACE (Free-Air CO2 Enrichment) s ite at the Duke Forest, we assessed the responses of the litter microarthro pod assemblage to elevated CO2 (200 ppm above ambient) in a loblolly pine p lantation. Following the initiation of the elevated CO2 treatment, a trend toward lower microarthropod abundance under elevated CO2 emerged. After 18 months, the mean microarthropod abundance was 33% lower in the elevated tre atment (P=0.04). The decline was evident in all microarthropod groups, but was significant only in the oribatid mites (P=0.04). Because these response s precede any changes in litter quality resulting from the CO2 treatment, t hey may reflect plant-derived changes in the soil that are being conveyed i nto the litter layer.