The significant contribution of fungi to soil N2O production across diverse ecosystems

Sporadic observations from pure culture study and direct soil measurement have indicated that fungi can substantially contribute to soil N2O production. Yet, it is still uncertain whether this fungal significance is a more general ecological phenomenon. In this study, relative contributions of fungi and bacteria to soil N2O production were examined in five ecosystems, including conventional farming (CON), integrated crop and livestock system (ICL), organic farming (ORG), plantation forestry (PF), and abandoned agriculture field subjected to natural succession (SUCC). Soil N2O production was measured at 90% water-filled pore space from antibiotic-free controls and soils amended with streptomycin, cycloheximide, or both. Streptomycin and cycloheximide additions significantly reduced soil N2O fluxes from the five systems, ranging from 31% to 54% and 40% to 51%, respectively. Fungi contributed more to soil N2O fluxes than bacteria in PF, whereas fungi and bacteria made comparable contributions in other four systems. Furthermore, soil pH was correlated positively with the percentage of bacterial contribution to soil N2O flux, but negatively with the percentage of fungal contribution to soil N2O flux as well as the ratio of fungal-to-bacterial contributions. Our results showed that fungi could potentially contribute to soil N2O prbduction in diverse agroecosystems and their contribution might be more pronounced in the acidic plantation forestry. (C) 2013 Elsevier B.V. All rights reserved.