Soil carbon in the South Atlantic United States: Land use change, forest management, and physiographic context

• Published in: Forest ecology and management 2022-09, Vol.520, p.120410, Article 120410
• Main Authors: Nave, Lucas E., DeLyser, Kendall, Domke, Grant M., Holub, Scott M., Janowiak, Maria K., Ontl, Todd A., Sprague, Eric, Viau, Nickolas R., Walters, Brian F., Swanston, Christopher W.
• Format: Article
• Language: English
• Subjects: Best management practices; Carbon management; Fire; Harvest; Meta-analysis; Plantation
• ISSN: 0378-1127; 1872-7042
• DOI: 10.1016/j.foreco.2022.120410

•Physiographic factors control baseline soil carbon stocks across the region.•Harvest impacts on soil carbon depend on interaction between place and practice.•Reforestation of cultivated soils increases surface soil carbon stocks.•Prescribed fire decreases surface soil carbon stocks.•Existing best management practices carry soil carbon co-benefits. Evidence-based forest carbon (C) management requires identifying baseline patterns and drivers of soil organic carbon (SOC) stocks, and their responses to land use change and management, at scales relevant to landowners and resource professionals. The growth of datasets related to SOC, which is the largest terrestrial C pool, facilitates use of synthesis techniques to assess SOC stocks and changes at management-relevant scales. We report results from a synthesis using meta-analysis of published studies, as well as two large databases, in which we identify baseline patterns and drivers, quantify influences of land use change and forest management, and provide ecological context for distinct management regimes and their SOC impacts. We conducted this, the fourth in a series of ecoregional SOC assessments, for the South Atlantic States, which are disproportionately important to the national-scale forest C sink and forest products industry in the U.S. At the ecoregional level, baseline SOC stocks vary with climatic, topographic, and soil physical factors such as temperature and precipitation, slope gradient and aspect, and soil texture. Land use change and forest management modestly influence SOC stocks. Reforestation on previously cultivated lands increases SOC stocks, while deforestation for cultivation has the opposite effect; for continuously forested lands, harvesting is associated with SOC increases and prescribed fire with SOC declines. Effects of reforestation are large and positive for upper mineral soils (+30%) but not detectable in lower mineral soils. Negative effects of prescribed fire are due to significant C losses from organic horizons (-46%); fire and harvest have no impacts on upper mineral soils but both increase SOC in lower mineral soils (+8.2 and +46%, respectively, with high uncertainty in the latter). Inceptisols are generally more negatively impacted by prescribed fire or harvest than Ultisols, and covariance between inherent factors (including soil taxonomy) and management impacts indicates how interior vs. coastal physiographic sections differ in their management regimes and SOC trends. In