Carbon in heartwood, sapwood and bark along stem profile in three Mediterranean Pinus species

Context: Understanding biological processes in forests is necessary to orientate ecosystem management towards potential C sequestration. To achieve this, information is required about changes in forest biomass C pools, including the stem components (bark, sapwood and heartwood). Aims: This study aimed to determine whether there are differences in C concentration in axial and radial directions within stem biomass in Pinus nigra, Pinus pinaster and Pinus sylvestris. Methods: Wood samples from a permanent plantation in northern Spain were examined for C concentration and wood bulk density: Results: The results showed that C concentration was higher in heartwood than in sapwood in the three species. Pinus spp. sapwood C concentration increased along the stem, while the C concentration in heartwood tissue showed the opposite behavior. In bark, Pinus pinaster showed a decreasing trend, in contrast to Pinus nigra and Pinus sylvestris, where higher values were found at the base and top of the stem. Finally, wood bulk density decreased in heartwood, sapwood and bark areas when stem height increased. Estimating C content taking account different anatomical parts and heights is important in considering the specificy of the different parts because of their potential commercial or ecological use in the forest ecosystems.