Contrasting effects of bamboo leaf and its biochar on soil CO2 efflux and labile organic carbon in an intensively managed Chinese chestnut plantation

The effects and associated mechanisms of the application of organic residues or their derived biochar on the dynamics of soil organic C and soil CO2 efflux in planted soils are poorly understood. This paper investigated the impact of bamboo leaf and the derived biochar applications on soil CO2 efflux and labile organic C in an intensively managed Chinese chestnut plantation in a 12-month field study. The treatments studied included Control, application of bamboo leaf (Leaf), and application of biochar (Biochar). The Leaf treatment increased (P < 0.05) soil CO2 efflux and concentrations of water-soluble organic C (WSOC) and microbial biomass C (MBC). The Biochar treatment increased soil CO2 efflux and WSOC and MBC only in the first month after application, but such effects diminished thereafter. The annual cumulative soil CO2 emission was increased by 16 % by the Leaf treatment as compared to the Control, but there was no difference between the Biochar and Control treatments. The soil organic C (SOC) storage was increased by biochar addition but not by bamboo leaf addition. An exponential relationship between soil temperature and soil CO2 efflux was observed regardless of the treatment. Soil CO2 efflux was correlated to soil WSOC (P < 0.05) but not to soil MBC or moisture content. The apparent temperature sensitivity (Q10) of soil CO2 efflux was ranked as Leaf > Biochar > Control. In comparison with the application of fresh bamboo leaf, pyrolyzed bamboo leaf (biochar) application decreased CO2 effluxes and increased C sequestration in the soil.