Nitrogen and water addition regulate fungal community and microbial co-occurrence network complexity in the rhizosphere of Alhagi sparsifolia seedlings

Abstract Rhizosphere microbes are key regulators of phreatophyte establishment in extremely arid environments. Although it is known that increased nitrogen (N) deposition alters microbial communities in arid lands, the effect of N enrichment in soil on phreatophyte rhizospheric microbes remain poorly understood. In a mesocosms experiment, we characterized the diversity, composition of rhizospheric bacterial and fungal communities of Alhagi sparsifolia seedlings by high-throughput sequencing in four-level N additions under drought and well-watered regimes. The relationships between microbial communities and soil properties and plant traits were also quantified. N interacted with water explained the 42.1% variation on fungal community composition, and significantly altered their alpha-diversity which positively correlated with proline accumulation in leaves, while the rhizobacterial community exhibited stability to N and water inputs. The Mantel test showed that microbial community composition at the OTU level was interrelated to soil properties and plant traits. Co-occurrence network analyses suggested that low N input (0–3 g m−2 year−1) and drought stress caused more complex associations along with vulnerability to environmental interference. Our results proposed that rhizosphere bacterial and fungal communities of phreatophyte respond differently to N enrichment under divergent water regimes. Climate change could potentially affect desert plant-microbe interactions. These findings can contribute to predicting and managing ecological and evolutionary responses of the desert ecosystem under global changing scenarios.