Alien invasive plant Amaranthus spinosus mainly altered the community structure instead of the α diversity of soil N-fixing bacteria under drought

Abstract Soil N-fixing bacteria (SNFB) may be vital to the invasion process of invasive alien plants (IAPs). Further, SNFB may be altered under drought which can affect the invasion process of IAPs. This study aims to estimate the differences in the α diversity and β diversity of SNFB between the infamous IAP Amaranthus spinosus L. (a spinous annual or perennial herb weed; originates from tropical America) and the native species A. tricolor L. (an annual herb crop) under various degrees of drought (i.e., control, and low, medium, and high degrees of drought, respectively). Drought significantly declines soil pH, water content, and electrical conductivity. Drought significantly rises soil microbial biomass carbon but poses unobvious impacts on the α diversity of SNFB. A. spinosus recruits indistinctive impacts on soil pH, water content, and electrical conductivity as well as the α diversity of SNFB. Drought and A. spinosus significantly affect the β diversity of SNFB. Further, some SNFB taxa have been significantly altered under drought and A. spinosus (i.e., f_Bradyrhizobiaceae under high degree of drought; p_uncultured_bacterium in the rhizosphere soil of monocultural A. spinosus) according to the results of the LEfSe analysis. Thus, drought and A. spinosus are largely changed the community structure of SNFB instead of the α diversity of SNFB.