Biochar amendments increase soil organic carbon storage and decrease global warming potentials of soil CH4 and N2O under N addition in a subtropical Moso bamboo plantation

摘要

Background: Nitrogen(N) deposition affects soil greenhouse gas(GHG) emissions, while biochar application reduces GHG emissions in agricultural soils. However, it remains unclear whether biochar amendment can alleviate the promoting effects of N input on GHG emissions in forest soils. Here, we quantify the separate and combined effects of biochar amendment(0, 20, and 40 t·ha) and N addition(0, 30, 60, and 90 kg N·ha·yr) on soil GHG fluxes in a long-term field experiment at a Moso bamboo(Phyllostachys edulis) plantation.Results: Low and moderate N inputs(≤60 kg N·ha·yr) significantly increase mean annual soil carbon dioxide(CO) and nitrous oxide(NO) emissions by 17.0%–25.4% and 29.8%–31.2%, respectively, while decreasing methane(CH) uptake by 12.4%–15.9%, leading to increases in the global warming potential(GWP) of soil CHand NO fluxes by 32.4%–44.0%. Moreover, N addition reduces soil organic carbon(C;SOC) storage by 0.2%–6.5%. Compared to the control treatment, biochar amendment increases mean annual soil CO2emissions, CHuptake, and SOC storage by 18.4%–25.4%, 7.6%–15.8%, and 7.1%–13.4%, respectively, while decreasing NO emissions by 17.6%–19.2%, leading to a GWP decrease of 18.4%–21.4%. Biochar amendments significantly enhance the promoting effects of N addition on soil COemissions, while substantially offsetting the promotion of N2O emissions, inhibition of CHuptake, and decreased SOC storage, resulting in a GWP decrease of 9.1%–30.3%.Additionally, soil COand CHfluxes are significantly and positively correlated with soil microbial biomass C(MBC) and pH. Meanwhile, NO emissions have a significant and positive correlation with soil MBC and a negative correlation with pH.Conclusions: Biochar amendment can increase SOC storage and offset the enhanced GWP mediated by elevated N deposition and is, thus, a potential strategy for increasing soil C sinks and decreasing GWPs of soil CHand NO under increasing atmospheric N deposition in Moso bamboo plantations.