Dynamics of biomass and carbon sequestration across a chronosequence of masson pine plantations

Abstract

Abstract The changes of forest biomass stock and carbon (C) sequestration with stand ages at fixed intervals in the different vegetation components remain unknown. Using the masson pine ( Pinus massoniana ) relative growth equation, biomass carbon stocks were obtained in four masson pine plantations at 12 year intervals (3 years, 15 years, 27 years, and 39 years). Meanwhile, the changes in soil organic C (SOC) stock with stand ages were also estimated. The biomass stock varied from 1.41 to 265.33 Mg ha −1 , 6.87 to 7.49 Mg ha −1 , and 2.66 to 4.86 Mg ha −1 in the tree, shrub, and herb layers. Carbon concentrations in plant tissues were 51.6%, 39.0%, and 42.2% in the tree, shrub, and herb layers. The aboveground biomass C contributed 81.7% and 60.5% in the tree and shrub layers, and the root to shoot (R/S) ratio of the tree and shrub layer biomass averaged 0.23 and 0.69. Biomass C stock increased significantly ( p < 0.05) with forest age, whereas the changes in biomass accumulation rate decreased significantly ( p < 0.05). The annual net C sequestration increased with age from 0.47 to 9.83 Mg ha −1 yr −1 in the tree layer but decreased in the shrub and herb layers. The SOC content decreased with soil depth but increased with age, whereas the SOC stock increased with depth and age. However, the total ecosystem C stock increased significantly ( p < 0.05) with stand age suggesting that age is the controlling factor of photosynthetic and biological processes and thus changes in biomass accumulation and C sequestration in masson pine plantations. Therefore, in‐depth studies are needed for continuous monitoring of the changes in nutrients and elements cycling with stand ages in this forest ecosystem.