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

Soil bacterial community could be affected by Amaranthus retroflexus L

Invasive plants can disrupt the growth performance of native plants by releasing allelochemicals affecting on litter decomposition. Furthermore, these invaders can establish a plant-soil feedback loop with soil microorganisms, which promotes their continued successful invasion primarily through decomposition process. Consequently, it is of the utmost importance to conduct research that analyzes the impacts of invasive plants' allelopathy on their interaction with soil microorganisms. This study aims to investigate the effects of Amaranthus retroflexus L., an invasive Amaranthaceae plant's allelopathy, on its interaction with soil bacterial communities, compared to the native plant A. tricolor L., and also the impacts of the allelopathy of Amaranthus retroflexus on soil enzyme activities. The research was conducted via an indoor planting experiment in which a gradient of Amaranthus retroflexus leaf litter was added. In particular, Amaranthus retroflexus leaf litter resulted in an increase in pH, electrical conductivity, total nitrogen, and neutral protease activity in soil under certain treatments. The amount of Amaranthus retroflexus leaf litter and the form of incubation condition may be the primary determinants of the composition of bacterial communities in soil and the number of functional gene pathways of soil bacteria involved in the decomposition process (especially the decomposition of carbon-containing substances), rather than the alpha diversity of soil bacteria. Consequently, Amaranthus retroflexus may predominantly modify the composition of bacterial communities in soil and the number of functional gene pathways of soil bacteria involved in the decomposition process, rather than the alpha diversity of soil bacteria, to facilitate its subsequent invasion.