Effects of biochar addition on the mineralization of native soil organic carbon in Cunninghamia lanceolata plantation.

Abstract

Effects of addition of different biochars on soil organic carbon (SOC) mineralization were studied by the 13C-labelling technique for a better understanding of biomass resource utilization and carbon sequestration in subtropical Chinese fir (Cunninghamia lanceolata) plantation. An incubation experiment under 25 ℃ was performed over a period of 112 days to address how different biochar addition would affect the mineralization of native SOC. Biochars were produced from Schimasuperba or C. lanceolata litter at 350, 550 and 750 ℃, respectively. Results showed that the mineralization of native SOC was significantly accelerated during the first three days and subsequently suppressed from 7 to 112 days of incubation after C. lanceolata biochar addition compared to the control. In the S. superba biochar addition treatment, there was a significant increase in mineralization of native SOC within the first 14 days of incubation and then a rapid decrease from days 28 to 112. After 112 days incubation, all the three C. lanceolata biochar (350, 550 and 750 ℃) additions significantly inhibited the mineralization of native SOC. A similar trend was observed for the two S. superba biochar (350 and 550 ℃) additions but not for the S. superba biochar (750 ℃) addition. The decomposition rates of S. superba biochar and C. lanceolata biochar were 0.8%-2.8% after 112 days incubation and decreased with the increases of pyrolysis temperature. Under the same pyrolysis temperature, the decomposition rate of the S. superba biochar was significantly higher than that of the C. lanceolata biochar. In conclusion, both the raw material and pyrolysis temperature of biochars would be important factors driving the mineralization of native SOC and biochar degradation.