Impact of root diversity upon coupling between soil C and N accumulation and bacterial community dynamics and activity: Result of a 30Â year rotation experiment

Many ecosystem functions and processes depend on biodiversity, however, the effect of root diversity in agroecosystems on soil bacterial communities and processes remained largely unknown. Our objectives were to examine the importance of increased root diversity through crop rotation on soil bacterial community composition and its relationship with soil carbon (C) and nitrogen (N) accumulation, which play an important role in soil fertility. In a field experiment with 30-year crop rotation, where there was no difference in root biomass input in top soil, soil C and N accumulation rates, soil microbial activities and bacterial community composition were investigated. Soil C and N accumulation rates and microbial biomass content were generally increased after rotation, with a greater increase in legume-cereal rotation than in cereal-cereal rotation. Crop rotation also increased soil microbial activity (soil respiration, potential N mineralization), but did not affect soil bacterial diversity. The increased bacterial abundance and changes in bacterial community structure and abundances of dominant bacterial phyla in rotation soils were related to increases in soil C and N accumulation and microbial activity. Our results suggest that increased root diversity through rotation can influence soil bacterial community structure and increase soil fertility by enhancing C and N accumulation rates, and cause positive effects on soil organic C and fertility. The influence of legume-cereal rotation was greater than that of cereal-cereal rotation.