Carbon amendments are known to influence microbial activity and soil nutrient availability.  A study was conducted to characterize the effects of different levels of post-harvest organic matter retention on microbial cycling of nitrogen (N), phosphorus (P) and carbon (C) in a loblolly pine plantation clearcut in 2004.  Field treatments included: control (25 Mg ha^-1 forest floor), raked (25 Mg ha^-1 forest floor removed), double forest floor (25 Mg ha^-1 forest floor added), and two mulched treatments (25 and 50 Mg ha^-1 of logging debris).  Soil samples were collected from three depths (0-20, 20-40, 40-60 cm) in May, July and October of 2006, and assessments on these samples included determinations of: microbial biomass N, P, and C, extractable N and P, microbial resource limitations, and soil labile organic carbon pools.  To date, results from these analyses have shown that the plots treated with two levels of mulched logging debris have significantly higher microbial biomass C than the other treatments.  These initial results suggest that the management of post harvest forest floor and logging debris can significantly influence soil microbial activity in loblolly pine plantations.