plantations on the Virginia Piedmont and South Carolina Coastal Plain over a rotation-length chronosequence

We measured sol1 surface C02 cfflux (F,) 111 loblolly ptnc stands ( P m u ~ t~red~i L ) located on the Vtrglnia Plcdmont (VA) and South Carollna Coastal Platn (SC) In cfforts to assess the lnlpact cl~matc, productlv~ty, and cultural practlccs have on F, in the managed loblolly plnc ecosystem The cffect of qtand dge on F, was cxamlncd using a rcplicaled chronoscqucncc approach In whlch stands ranging from 1 to 25 years slncc plallltng were lnvestlgated Soil COz cfflux was ~ncasured on both VA and SC sites for over a ycar using a closed dynamlc system Multiple lillear regrcsslon was used to evaluate F, correlates and examlnc the rclatlonshlp betweell candidate explanatory vartablcs and F, So11 temperature (top 10 cm) was the major correlate wlth F, on both locattons We obscrvcd a posltivc age effect on F, in VA stands and no rclatlonshlp between age and F, in SC stands Annual sot1 C efflux decltncd wlth stand age In SC due to both reduct~ons In soil temperatures as crown closure occurs and a diminishing heterotrophlc C substrate pool. Annual cstllnated cfflux ranges from 16.7 to 13.2 Mg C ha-' for 1 and 20-year-old stands, rcspectlvely In contrast, annual so11 C cfflux lncrcased wlth age tn VA stands as a result of the posltrve relationship bctwccil stand age and F,, which appears to be related to an increase In the contrlbut1011 of root respiration to total F, over time In VA stands, cfflux cstlmates range from 7 6 to 12 3 Mg C ha-' for 1 and 20-ycdr-old stands, rcspecttvcly These results demonstrate the need to furthe1 consider the impact forcst management dnd wlthln-rcglon varlabllity have on sol1 C cfflux over tlmc when estimating C budgets