Partitioning soil respiration across four age classes of loblolly pine (Pinus taeda L.) on the Virginia Piedmont

•RH is partitioned from RS in managed loblolly pine plantations.•Estimates of RH:RS is needed to calculate annual forest NEP.•Stand age, season, and stand characteristics influence RH:RS.•RH:RS declines as stand age increases. Quantification of the heterotrophic component of total soil respiration is important for estimating forest carbon pools and fluxes, and for understanding carbon dynamics associated with stand development and silvicultural management. We measured the proportion of heterotrophic respiration (RH) to total soil respiration (RS) in extensively managed loblolly pine (Pinus taeda L.) stands of four age classes in the Piedmont physiographic province of Virginia. Our objectives were to evaluate the influence of stand age and seasonality on the proportion of RH to RS (RH:RS). RH was partitioned using root exclusion cores, and both RS and RH were measured 90days following installation of cores for five seasons. Repeated measures analysis revealed that stand age and measurement season each had a significant effect on RH:RS (P