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

Background While soil organic matter 13 C isotope helped evaluate vegetation-related change in soil organic carbon (SOC), less is understood about δ 13 C SOC and SOC in reforested ecosystems. Methods To assess native vegetation (vegetation predominant in the region prior to deforestation) and the effect of reforestation on SOC, we studied δ 13 C of plant, litter and SOC in reforested red pine, chestnut, mixed stands and silvergrass, and compared them with bare land. Results 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. δ 13 C SOC in red pine, chestnut, mixed stands, and bare land increased (∆ 13 C 2.4–5.9‰) from L-layer to 1 m soil depth and indicated C 3 vegetation was long-term component of the area. In contrast, δ 13 C SOC values are more depleted than expected in silvergrass (∆ 13 C −9.7‰), and similar to reforested soil. This indicates its recent colonization in area occupied previously by C 3 species. Regression coefficient- β , indicated isotopic fractionation during SOC decomposition/humification and physical mixing that occurs during C turnover in well-drained soil. The δ 13 C 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. Conclusion Results suggest that reforested species impact soil C decay rate and turnover, and soil ability to maintain SOC stocks post deforestation.