Environmental and stand management influences on soil CO2 efflux across the range of loblolly pine

• Soil respiration data was collected from 154 plots across 11 states.
• Four-parameter model explained 56% of variation in Rs across the range of loblolly pine.
• Thinning and fertilization did not influence Rs rates, but did impact Rh.
• Forest management may shift relative contributions of heterotrophic and root respiration.

Managed loblolly pine forests comprise an important pool in the global carbon cycle. Understanding the factors impacting fluxes from this pool, including the effects of management activities, will help provide more accurate and precise estimates of carbon pools and allow landowners and policy makers to better manage loblolly pine stands for carbon sequestration. Specific to this study, we sought to create regional models for soil CO2 efflux (Rs) using data collected from 154 plots across 11 states representing the managed range of loblolly pine in the southeastern United States. We also examined an index of heterotrophic respiration (Rh) using root free soil incubations. Additionally, these data were examined to determine the effects of fertilization and thinning on Rs and Rh index. The Rs model (R2 = 0.56) included soil temperature, latitude, a soil moisture by soil temperature effect, soil nitrogen, and bulk density variables. The Rh index (R2 = 0.45) model included soil moisture, temperature, percent coarse fragments, and elevation. Rs was not significantly affected by either fertilization or thinning, yet Rh index was influenced by both (negatively and positively, respectively). This indicates a shift in relative contributions of heterotrophic respiration and root respiration components to Rs in response to these treatments.