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

Abstract

Ammonia (NH3) emissions, the most important nitrogen (N) loss, always induce a series of environmental problems such as increased the frequency of regional haze pollution, accelerated N deposition, and N eutrophication. Arbuscular mycorrhizal (AM) fungi play key roles in N cycling. However, whether AM fungi can alleviate N losses by reducing NH3 emissions is still unclear. The potential and mechanism by which AM fungi reduce NH3 emissions in five land-use types (grazed grassland, mowed grassland, fenced grassland, artificial alfalfa grassland, and cropland) were explored in this study. The results showed that AM fungal inoculation significantly reduced NH3 emissions and the mycorrhizal responses of NH3 emissions were determined by land-use type. Structural equation modeling (SEM) showed that AM fungi and land-use type directly affected NH3 emissions. In addition, the reduction in NH3 emissions was largely driven by the decline in soil NH4+-N and pH and the increase the abundances of ammonia-oxidizing archaea (AOA) and bacteria (AOB), urease activity and plant N content 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.