Does Bidens pilosa L. Affect Carbon and Nitrogen Contents, Enzymatic Activities, and Bacterial Communities in Soil Treated with Different Forms of Nitrogen Deposition?

The deposition of nitrogen in soil may be influenced by the presence of different nitrogen components, which may affect the accessibility of soil nitrogen and invasive plant–soil microbe interactions. This, in turn, may alter the success of invasive plants. This study aimed to clarify the influences of the invasive plantBidens pilosaL. on the physicochemical properties, carbon and nitrogen contents, enzymatic activities, and bacterial communities in soil in comparison to the native plantPterocypsela laciniata(Houtt.) Shih treated with simulated nitrogen deposition at 5 g nitrogen m−2yr−1in four forms (nitrate, ammonium, urea, and mixed nitrogen). MonoculturalB. pilosaresulted in a notable increase in soil pH but a substantial decrease in the moisture, electrical conductivity, ammonium content, and the activities of polyphenol oxidase, β-xylosidase, FDA hydrolase, and sucrase in soil in comparison to the control. Co-cultivatingB. pilosaandP. laciniataresulted in a notable increase in total soil organic carbon content in comparison to the control. MonoculturalB. pilosaresulted in a notable decrease in soil bacterial alpha diversity in comparison to monoculturalP. laciniata. Soil FDA hydrolase activity and soil bacterial alpha diversity, especially the indices of Shannon’s diversity, Simpson’s dominance, and Pielou’s evenness, exhibited a notable decline under co-cultivatedB. pilosaandP. laciniatatreated with nitrate in comparison to those treated with ammonium, urea, and mixed nitrogen.