Effect of atmospheric N deposition on rhizosphere soil microbial community composition in a semi-arid grassland

Aims: Human activities have more than doubled the input of atmospheric reactive nitrogen into terrestrial ecosystems, affecting plant and soil microbial communities. This study aimed to investigate the effect of atmospheric N deposition on the rhizosphere soil microbial community composition of the main plant species with different niches in grassland. Methods: An N addition experiment was performed in a semi-arid grassland on the Loess Plateau, China. The experiment consisted of four N addition treatments: N0 (0 g N m⁻² yr⁻¹), N3 (3 g N m⁻² yr⁻¹), N6 (6 g N m⁻² yr⁻¹), and N9 (9 g N m⁻² yr⁻¹). The response of rhizosphere soil microbial community composition from four main plant species to atmospheric N deposition was explored. Results: Nitrogen addition significantly affected rhizosphere soil bacterial community composition of Bothriochloa ischaemum and Stipa bungeana but had no effect on that of Artemisia gmelinii and Cleistogenes squarrosa. Furthermore, it also significantly affected rhizosphere soil fungal community composition of S.bungeana; however, no effects were observed on the other three plant species. Compared with the complexity of rhizosphere soil bacterial network, low N addition rates had a greater effect on the complexity of the rhizosphere soil fungal network. Conclucsions: This study revealed that rhizosphere soil bacterial community composition of plant species with a higher niche breadth is generally more sensitive to atmospheric N deposition. Our study highlights the distinct roles of plant species with different niche breadths in maintaining rhizosphere soil microbial community composition under conditions of global N enrichment.