Carbon emissions from stumps vary by species but not sprouting in a temperate hardwood forest

Cut stumps can be temporary hot spots of carbon emissions due to connections to decaying root systems. Drivers of variation in stump decomposition have yet to be clearly identified, including interactions with stump sprouting, an important regeneration pathway after harvest in temperate deciduous forests. The aim of this study was to identify the effects of sprouting relative to other abiotic and biotic factors on carbon emissions from cut stumps. We measured carbon dioxide (CO₂) and methane (CH₄) flux from the surface of cut stumps 0-4 years following a canopy gap harvest in an upland mixed-oak forest in the southern Appalachians, U.S. Stumps were a CO₂ source for all years with flux values ranging from 0.14 to 227.5 μmol CO₂ m^-2 s^-1. Instantaneous CH₄ flux was largely positive (81 %) and ranged from -0.32 to 201.6 nmol CH₄ m^-2 s^-1. Sprouting did not affect CO₂ or CH₄ flux despite decreasing stump surface temperature and increasing wood moisture. Both CO₂ and CH₄ flux were stable over time since harvest and differed most strongly by genus. Using an average annual C-CO₂ emission rate of 2.6 kg C m^-2 of stump surface yr^-1 and preharvest basal area (42 m² ha^-1), the annual C-CO₂ loss from stumps was estimated to be 109 kg C ha^-1 yr^-1 (16.6 and 800.2 kg C ha^-1 yr^-1 95CI) near-term to gap harvest. Understanding factors influencing the variability in carbon emissions from stump decomposition is critical as we test sustainable forest management approaches that optimize climate change adaptation and mitigation.