Effects of biochar addition on CO2 and CH4 emissions from a cultivated sandy loam soil during freeze-thaw cycles

This study was conducted to examine the effects of biochar additions (0, 2 and 4%, w/w) on soil carbon dioxide (CO2) and methane (CH4) emissions during freeze-thaw cycles (FTC). The results showed that soil CO2 emissions were stimulated by both FTC and biochar addition. However, the differences in soil CO2 emissions between control (CK) and FTC treatments were not significant when biochar addition rate was 4%, indicating that high biochar addition rate may have stronger effect on stimulating soil CO2 emissions than FTC. The increased soil dissolved organic carbon content, which attributed to the labile carbon in biochar, was the likely reason for the increased CO2 emissions. The negative CH4 emissions were promoted by biochar, especially under FTC conditions; possibly due to the structure of biochar soil aeration increased, which formed a favourable environment for methanotrophs. The results of this study indicate that biochar additions can increase soil CO2 emissions and CH4 uptakes during FTC, and such effects are different from those under CK conditions.