Site related δ^sup 13^C of vegetation and soil organic carbon in a cool temperate region

While soil organic matter 13C isotope helped evaluate vegetation-related change in soil organic carbon (SOC), less is understood about δ13CSOC 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 δ13C 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. δ13CSOC in red pine, chestnut, mixed stands, and bare land increased (∆13C 2.4–5.9‰) from L-layer to 1 m soil depth and indicated C3 vegetation was long-term component of the area. In contrast, δ13CSOC values are more depleted than expected in silvergrass (∆13C −9.7‰), and similar to reforested soil. This indicates its recent colonization in area occupied previously by C3 species. Regression coefficient-β, indicated isotopic fractionation during SOC decomposition/humification and physical mixing that occurs during C turnover in well-drained soil. The δ13CSOC 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.