Arbuscular mycorrhizal fungi reduce ammonia emissions under different land-use types in agro-pastoral areas

Ammonia(NH3) emissions, the most important nitrogen(N) loss form, always induce a series of environmental problems such as increased frequency of regional haze pollution, accelerated N deposition, and N eutrophication. Arbuscular mycorrhizal(AM) fungi play key roles in N cycling. However, it is still unclear whether AM fungi can alleviate N losses by reducing NH3emissions. The potential mechanisms by which AM fungi reduce NH3emissions in five land-use types(grazed grassland, mowed grassland, fenced grassland, artificial alfalfa grassland, and cropland) were explored in this study. Results showed that AM fungal inoculation significantly reduced NH3emissions, and the mycorrhizal responses of NH3emissions were determined by land-use type. Structural equation modeling(SEM) showed that AM fungi and land-use type directly affected NH3emissions. In addition, the reduction in NH3emissions was largely driven by the decline in soil NH4+-N and pH and the increases in abundances of ammonia-oxidizing archaea(AOA) amoA and bacteria(AOB) amoB genes,urease activity, and plant N uptake induced by AM fungal inoculation and land-use type. The present results highlight that reducing the negative influence of agricultural intensification caused by land-use type changes on AM fungi should be considered to reduce N losses in agriculture and grassland ecosystems.