The invasive Alternanthera philoxeroides modifies the sediment microbiome in urban and periurban river wetlands

Few studies have evaluated the invasive effects on soil properties in urban ecosystems. In this study, population density and impervious surface area were used to divide the two river wetlands of Qingdao City, China— River Zhangcun and River Wenquan—into urban and periurban types. Sediments were sampled from plots colonized by the invasive Alternanthera philoxeroides and the native Typha angustifolia in these two river wetlands. The sediment properties, including fertility, stoichiometry, microbial diversity indices (observed species, Chao1, Shannon’s diversity index and Simpson’s diversity index) and species composition, were evaluated and compared. We found similar fertility and stoichiometry between sediments derived from invasive and native species. A greater bacterial diversity was found in the sediment derived from A. philoxeroides in the periurban river, while a greater fungal diversity was merely shown for the Shannon’s diversity index of A. philoxeroides regardless of river types. In addition, more microbes relevant to nutrient cycling processes, such as denitrification, accumulated in response to invasion, which may have decreased the habitat quality and impeded the invasion of T. angustifolia into A. philoxeroides populations. The discrepancy in urbanization status affected the impact of plant colonization on sediment properties, and the opposite results were shown for the comparisons of sediment nitrogen availability and bacterial diversity between the two species. Urbanization discriminated the impact of invasion to some degree. The invasion of A. philoxeroides altered the sediment microbiome, and the potential plant‒soil feedback needs further investigation.