Data from: Ecosystem carbon density and allocation across a chronosequence of longleaf pine forests in the southeastern USA

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 five to 118 years located across the southeastern USA 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% to 22% of ecosystem C. Soil C was related to site index, but not to stand age, and comprised 39% to 92% of ecosystem C. Live understory C, forest floor C, down 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.

森林可通过活体生物量的提升部分抵消温室气体排放，助力气候变化减缓。本研究对美国东南部分布的20片人工经营长叶松（Pinus palustris Mill.）林开展碳（C）密度量化工作，这些林分的林龄跨度为5至118年，并估算了其地上与地下碳动态轨迹。生态系统碳库（涵盖土壤碳在内的全部碳库）与地上活立木碳储量均随林分年龄呈非线性增长，模型拟合得到的渐近最大值分别为168 Mg C/ha与80 Mg C/ha。生态系统碳储量随林分年龄的积累过程主要由地上活立木碳储量的增长驱动，地上活立木碳储量范围为<1 Mg C/ha至74 Mg C/ha，占生态系统碳储量的比例介于<1%至39%之间。活体根系碳（包含伐桩下碳、探地雷达（ground penetrating radar）测定的侧根碳以及活体细根碳的总和）随林分年龄增长，占生态系统碳储量的4%至22%。土壤碳储量与立地指数显著相关，但与林分年龄无明显关联，其占生态系统碳储量的比例为39%至92%。林下活地被物碳、森林枯落层碳、倒木碳以及枯立木碳在这些高频火烧经营林分中占生态系统碳储量的比例均较低。林分年龄与立地指数可解释林分间76%的生态系统碳储量变异。以所有林分（排除草状阶段林分）的平均值计算得到的平均根冠比为0.54（标准差0.19），高于其他针叶林的相关研究报道。活立木碳的长期积累，加上侧根碳的地下积累占比相较于其他森林类型更高，表明长叶松林可提供抗干扰的碳储库，能够平衡集约经营森林伴随的更快碳积累与碳移除过程。尽管其他人工经营的南方松林系统在短期内可固存更多碳，但本研究认为长叶松林在区域森林碳管理中可发挥重要作用。