Contrasting short-term responses of soil heterotrophic and autotrophic respiration to biochar-based and chemical fertilizers in a subtropical Moso bamboo plantation

Application of biochar-based fertilizer (BF), produced by combining biochar with chemical fertilizer, is known to be an effective way to increase plant growth and soil organic carbon (SOC) stock, but its impact on soil respiration (RS) components and associated mechanisms in subtropical plantations remain unclear. The objectives of this 12-month field study were (1) to examine the effects of the application of a BF versus a chemical fertilizer (CF) on seasonal variations in soil heterotrophic (RH) and autotrophic (RA) respiration in a subtropical plantation of Moso bamboo (Phyllostachys edulis), and (2) to investigate relationships between soil RH and RA and soil environmental factors in different fertilizer treatments. Four treatments were tested: control (no fertilizer applied), BF application, CF application, and a 50: 50 mixture of BF and CF (BCF). Irrespective of the treatment, both RS and RH exhibited strong seasonal patterns. However, adding CF in the soil significantly increased the soil RH whereas BF decreased it (P < 0.05). Both CF and BF significantly (P < 0.05) increased soil RA. The RS, RH and RA were all exponentially related (P < 0.05) to soil temperature regardless of the treatment, and the Q₁₀ value of RH was greater than that of RA (P < 0.05). Applying CF increased the Q₁₀ for RH (P < 0.05), yet the application of BF did not affect it. Although the RS, RH and RA were not related to the soil moisture content in all treatments, both RS and RH were correlated (P < 0.05) with soil water soluble organic C and microbial biomass C concentrations, and also with soil invertase and β-glucosidase activities. In conclusion, compared with the conventional chemical fertilizer use, the novel management practice of biochar-based fertilizer application offers advantages, such as reducing soil C emissions and increasing SOC content, which has the implication of mitigating soil greenhouse gas emissions in subtropical Moso bamboo plantations.