Biomass and carbon storage in an age-sequence of Cyclobalanopsis glauca plantations in southwest China

Million-hectare plantations of Cyclobalanopsis glauca were planted in southwest China to restore the degraded vegetation. Although many studies of these plantations have been conducted, from the genetic scale to regional scales, the role of stand age in regional carbon (C) cycling remains unclear. In this study, we examined the biomass and C storage of the main ecosystem components in five C. glauca plantation stands in Guangxi Province, southwest China, that ranged in age from 8 to 70 years. The ecosystem and tree biomass increased with increasing stand age. On average, the highest C concentration was found in tree branches, whereas the lowest C concentration was found in the underground parts of herb. C concentration in trees, shrubs, herbs, and litter were age-dependent. C storage in C. glauca plant biomass in stands aged 8, 20, 40, 50, and 70 years was 40.45, 78.25, 90.41, 94.46, and 114.69 Mg ha−1, respectively. Soil organic C (SOC) storage in the top 1 m of soil in plantations aged 8, 20, 40, 50, and 70 years was 70.38, 90.84, 84.39, 47.91, and 107.99 Mg ha−1, respectively, with SOC concentration decreasing with increasing soil depth. Total C storage in the plantation ecosystem averaged 110.83, 169.09, 174.80, 142.37, and 222.68 Mg ha−1 in the 8-, 20-, 40-, 50-, and 70-year-old plantations, respectively, with most of the C storage in the aboveground biomass and soil rather than in the belowground biomass. Our results suggest that successional development as temporal factor influencing C storage in plantations are important considerations for fully realizing the ecological value of the C. glauca plantations in southwest China.