As part of a national-scale evaluation of the consequences of restoration and wildfire fuel reduction treatments in ecosystems that historically had frequent fire (www.ffs.fs.fed.us), we determined the effects of reintroduction of dormant season fire (functional restoration) and thinning from below (structural restoration) on soil organic matter characteristics and microbial activity in two mixed oak forests in the central hardwoods region, and contrasted them with the effects of the same treatments in two conifer forests. The hardwood forests were located on the Allegheny Plateau of southern Ohio (Ohio Hills/OH) and in the southern Appalachian Mountains of North Carolina (Green River/NC). The conifer forests were a pine- oak site in the Piedmont of South Carolina (Clemson Forest/SC) and a pine-fir site in the southern Cascades of northern California (Goosenest Adaptive Management Area/CA).