title: Ecosystem carbon density and allocation across a chronosequence of longleaf pine forests.
abstract: Forests can partially offset greenhouse gas emissions and contribute to climate change mitigation, mainly through increases in live biomass. We quantified carbon (C) density in 20 managed longleaf pine (Pinus palustris Mill.) forests ranging in age from 5 to 118 years located across the southeastern United States and estimated above- and belowground C trajectories. Ecosystem C stock (all pools including soil C) and aboveground live tree C increased nonlinearly with stand age and the modeled asymptotic maxima were 168 Mg C/ha and 80 Mg C/ha, respectively. Accumulation of ecosystem C with stand age was driven mainly by increases in aboveground live tree C, which ranged from <1 Mg C/ha to 74 Mg C/ha and comprised <1% to 39% of ecosystem C. Live root C (sum of below-stump C, ground penetrating radar measurement of lateral root C, and live fine root C) increased with stand age and represented 4-22% of ecosystem C. Soil C was related to site index, but not to stand age, and made up 39-92% of ecosystem C. Live understory C, forest floor C, downed dead wood C, and standing dead wood C were small fractions of ecosystem C in these frequently burned stands. Stand age and site index accounted for 76% of the variation in ecosystem C among stands. The mean root-to-shoot ratio calculated as the average across all stands (excluding the grass-stage stand) was 0.54 (standard deviation of 0.19) and higher than reports for other conifers. Long-term accumulation of live tree C, combined with the larger role of belowground accumulation of lateral root C than in other forest types, indicates a role of longleaf pine forests in providing disturbance-resistant C storage that can balance the more rapid C accumulation and C removal associated with more intensively managed forests. Although other managed southern pine systems sequester more C over the short-term, we suggest that longleaf pine forests can play a meaningful role in regional forest C management.
authors.affiliation: Center for Longleaf Pine Ecosystems, School of Forestry and Wildlife Sciences, Auburn University, Auburn, Alabama, 36849, USA.
authors.forename: Lisa J
authors.initials: LJ
authors.lastname: Samuelson
authors.affiliation: Center for Longleaf Pine Ecosystems, School of Forestry and Wildlife Sciences, Auburn University, Auburn, Alabama, 36849, USA.
authors.forename: Thomas A
authors.initials: TA
authors.lastname: Stokes
authors.affiliation: Southern Research Station, USDA Forest Service, University of Vermont, 81 Carrigan Drive, Aiken Center, Room 208, Burlington, Vermont, 05405, USA.
authors.forename: John R
authors.initials: JR
authors.lastname: Butnor
authors.affiliation: Southern Research Station, USDA Forest Service, 3041 Cornwallis Road, Research Triangle Park, North Carolina, 28809, USA.
authors.forename: Kurt H
authors.initials: KH
authors.lastname: Johnsen
authors.affiliation: School of Forest Resources and Conservation, University of Florida, P.O. Box 110410, Gainesville, Florida, 32611, USA.
authors.forename: Carlos A
authors.initials: CA
authors.lastname: Gonzalez-Benecke
authors.affiliation: School of Forest Resources and Conservation, University of Florida, P.O. Box 110410, Gainesville, Florida, 32611, USA.
authors.forename: Timothy A
authors.initials: TA
authors.lastname: Martin
authors.affiliation: School of Forest Resources and Conservation, University of Florida, P.O. Box 110410, Gainesville, Florida, 32611, USA.
authors.forename: Wendell P
authors.initials: WP
authors.lastname: Cropper
authors.affiliation: Southern Research Station, USDA Forest Service, 3041 Cornwallis Road, Research Triangle Park, North Carolina, 28809, USA.
authors.forename: Pete H
authors.initials: PH
authors.lastname: Anderson
authors.affiliation: Center for Longleaf Pine Ecosystems, School of Forestry and Wildlife Sciences, Auburn University, Auburn, Alabama, 36849, USA.
authors.forename: Michael R
authors.initials: MR
authors.lastname: Ramirez
authors.affiliation: Center for Longleaf Pine Ecosystems, School of Forestry and Wildlife Sciences, Auburn University, Auburn, Alabama, 36849, USA.
authors.forename: John C
authors.initials: JC
authors.lastname: Lewis
mesh_terms: D018533:Biomass; D057965:Carbon Sequestration; D065928:Forests; D028223:Pinus / Q000502:physiology*; D015144:Southeastern United States; D013997:Time Factors; D014197:Trees / Q000502:physiology*
keywords: 
  Pinus palustris
  ; carbon dynamics; carbon storage; chronosequence; forest structure; longleaf pine; root-to-shoot ratio; stand age