Effects of Forest Management and Land Use Change on Soil Carbon in the US Gulf Coastal Plain

Abstract The US Gulf Coastal Plain is a region of diverse forests and management systems and dynamic land use changes. These drivers affect carbon (C) stocks at ecosystem to regional scales, in turn affecting processes such as forest regeneration, hydrologic and biogeochemical cycling, and social and economic systems. We quantified land use change and forest management effects on C stocks in the Gulf Coastal Plain, focusing on soils, using two complementary approaches: meta-analysis of published literature and analysis of forest inventory data. Land use change had larger effects than forest management on soil C stocks at all scales. The direction and magnitude of change in soil C stocks differed among various types of land use change. From a regional perspective, the most important significant changes were those occurring with transfers between agricultural and forested land uses, though less extensive land uses also registered significant changes (e.g., wetland restoration, mine reclamation). Management of continuously forested land had subtler effects, which were focused on aboveground biomass and soil organic horizons. Organic horizons were consistently diminished by prescribed fire and may be reduced by harvesting, though evidence is limited for the latter, and declines are temporary in both cases. Aboveground activities intended to increase stand re-establishment and tree growth, such as competing vegetation control and fertilization, are at least compatible, and potentially synergistic with C storage in belowground pools. Overall, our results demonstrate how forest management can support forest C management and offer quantitative insights into specific management activities to aid researchers, policymakers, and practitioners.