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

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 (R-s) 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 (R-h) using root free soil incubations. Additionally, these data were examined to determine the effects of fertilization and thinning on R-s and R-h index. The R-s model (R-2 = 0.56) included soil temperature, latitude, a soil moisture by soil temperature effect, soil nitrogen, and bulk density variables. The R-h index (R-2 = 0.45) model included soil moisture, temperature, percent coarse fragments, and elevation. R-s was not significantly affected by either fertilization or thinning, yet R-h index was influenced by both (negatively and positively, respectively). This indicates a shift in relative contributions of heterotrophic respiration and root respiration components to R-s in response to these treatments. (C) 2015 Elsevier B.V. All rights reserved.