Ammonia-oxidizing archaea are more important than ammonia-oxidizing bacteria in nitrification and NO3 −-N loss in acidic soil of sloped land

Abstract

As part of a long-term sloped land use experiment established in 1995 at Taoyuan Agro-ecosystem Research Station (111°26′ E, 28°55′ N) in China, soil samples were collected from three land use types, including cropland (CL), natural forest, and tea plantation. Quantitative polymerase chain reaction and terminal restriction fragment length polymorphism were used to determine the abundance and community composition of amoA-containing bacteria (AOB) and archaea (AOA). The results indicate that land use type induced significant changes in soil potential nitrification rate and community composition, diversity, and abundance of AOB and AOA. Both AOB and AOA community compositions were generally similar between upper and lower slope positions (UP and LP), except within CL. The LP soils had significantly (p < 0.05) higher diversity and abundance of both AOB and AOA than in the UP. Potential nitrification rate was significantly correlated (p < 0.05) with diversity and abundance of AOA, but not with AOB. Among land use types, the NO3− and amoA-containing AOA runoff loss was greatest in CL. Nitrate-N runoff loss was significantly correlated (p < 0.05) with the loss of AOA amoA copies in the runoff water. Furthermore, relationships between NO3−-N runoff loss and abundance of AOA but not of AOB at both slope positions were significantly correlated (p < 0.05). These findings suggest that AOA are more important than AOB in nitrification and NO3−-N runoff loss in acidic soils across sloped land use types.