Abstract/Summary

Forest soil, especially temperate forest soil, is a prominent sink of atmospheric methane (CH4). Biochar has been increasingly applied to enhance CH4 uptake by soil. However, the effect of biochar size and temperature on CH4 uptake is still largely unknown. A series of incubation experiments were conducted to examine the single and combined effects of biochar addition and temperature (10 °C, 20 °C, and 30 °C) on CH4 uptake by temperate forest soil in China. The biochar was classified into three particle sizes (<0.1 mm, 0.1–0.5 mm, and 0.5–1 mm) and two application rates (0.73% and 3.65%, m: m). Results showed that the CH4 uptake was accelerated with the reduced particle sizes and the increased application rates of biochar. This variation was caused by two factors. Firstly, both the reduced particle sizes and increased application rates of biochar decreased the concentration of inorganic N, which had a negative relationship with CH4 uptake (P < 0.05). Secondly, the reduced particle sizes and increased application rates of biochar promoted both available phosphorus concentration and pH, and these two factors positively correlated with CH4 uptake (P < 0.05). The increased temperatures produced a negative effect on CH4 uptake (P < 0.05) due to the increased concentration of inorganic N after rising temperatures. Furthermore, the combined effect of biochar addition and increasing temperatures on CH4 uptake was antagonistic owing to the reduced Q10 value of CH4 uptake after biochar addition. This research highlights the importance of particle size of biochar on CH4 uptake. Our results also suggest that the positive effect of biochar addition on CH4 uptake may be dampened by global warming in the near future.