Site related δ13C of vegetation and soil organic carbon in a cool temperate region

While soil organic matter C-13 isotope helped evaluate vegetation-related change in soil organic carbon (SOC), less is understood about delta C-13(SOC) and SOC in reforested ecosystems. To assess native vegetation (vegetation predominant in the region prior to deforestation) and the effect of reforestation on SOC, we studied delta C-13 of plant, litter and SOC in reforested red pine, chestnut, mixed stands and silvergrass, and compared them with bare land. After 40 years, reforestation increased SOC by 82.86% and 24.90% in 0-10 cm and by 45.96% and 24.85% in 0-30 cm depths in chestnut and mixed stands, respectively. However, SOC content decreased in red pine and silvergrass in both 0-10 cm and 0-30 cm depths. delta C-13(SOC) in red pine, chestnut, mixed stands, and bare land increased (a dagger C-13 2.4-5.9aEuro degrees) from L-layer to 1 m soil depth and indicated C-3 vegetation was long-term component of the area. In contrast, delta C-13(SOC) values are more depleted than expected in silvergrass (a dagger C-13 -9.7aEuro degrees), and similar to reforested soil. This indicates its recent colonization in area occupied previously by C-3 species. Regression coefficient-beta, indicated isotopic fractionation during SOC decomposition/humification and physical mixing that occurs during C turnover in well-drained soil. The delta C-13(SOC) based estimated proportion of new carbon (f (new)) and decomposition rate (k) were higher in chestnut and mixed stand, and their turnover time was shorter than red pine and silvergrass. Results suggest that reforested species impact soil C decay rate and turnover, and soil ability to maintain SOC stocks post deforestation.