Interactive effects of biochar and AMF on plant growth and greenhouse gas emissions from wetland microcosms

Both biochar and arbuscular mycorrhizal fungi (AMF) can affect plant growth, but little is known about how the interaction between biochar and AMF affects greenhouse gas emissions from plant-soil systems. We tested the hypotheses that biochar and AMF can interact to affect greenhouse gas emissions due to promoted plant biomass and changed soil N availability. We assembled microcosms, each initially grown with three rarnets (vegetative individuals) of a clonal, wetland plant Phragmites australis, with or without AMF in soil and with or without biochar addition to soil. Biochar addition alone and AMF presence alone both significantly enhanced biomass of P. australis, but such effects became weaker when they were present simultaneously. The presence of AMF significantly decreased concentrations of chlorophyll and nitrogen (N) in P. australis and concentrations of NH4+-N, NO3--N, inorganic N and total N in soil, but such effects became weaker when biochar was added to soil than when it was not. Biochar addition significantly increased concentrations of chlorophyll and N in P. australis when AMF were present, but had little impact when AMF were absent. The presence of AMF increased CO2 emission and CO2 equivalent independent of biochar addition. The presence of AMF also increased N2O emission when biochar was added, but decreased it when biochar was not added. We conclude that biochar addition and AMF presence can interact to affect plant growth and N uptake, soil N availability and greenhouse gas emissions from plant-soil ecosystems.