Terrestrial vegetation and soils may act as important carbon sinks if risin
g atmospheric CO2 stimulates plant production. We used free-air CO2 enrichm
ent (FACE) technology to expose three 30 m diameter plots of a loblolly pin
e (Pinus taeda) forest to elevated CO2 at 200 mu L/L above ambient levels,
while three control plots were outfitted with FACE apparatus but were fumig
ated with ambient air. We quantified litterfall mass and chemistry, fine ro
ot biomass increment and turnover, CO2 efflux from soils, delta(13)C in soi
l CO2 soil CO2, soil microbial biomass C and N, and potential net N mineral
ization. After two growing seasons, elevated CO2 caused significant increas
es in loblolly pine litterfall mass and fine root increment. Within the fir
st year of FACE treatment, the concentration of CO2 in soil had increased,
and soil surface CO2 efflux was generally higher at elevated CO2, but this
difference was not statistically significant. Loblolly pine litter C:N rati
o, fine root turnover, microbial biomass C and N, and potential net N miner
alization were not significantly affected by elevated CO2. Our results sugg
est that elevated atmospheric CO2 may accelerate inputs of organic matter t
o soil C pools in loblolly pine forests, but it may also accelerate losses
of C from belowground by stimulating soil respiration.