Seasonal dynamics of ammonia-oxidizing archaea (AOA) and their contribution to nitrification in wheat rhizospheres

Aims

The temporal variations in ammonia-oxidizing archaea (AOA) abundance, diversity, ecological characteristics and nitrification rate in the wheat rhizosphere, as well as the impact of exogenous nitrogen addition were investigated. Our goal was to elucidate the role of AOA in the nitrogen cycle of wheat rhizosphere ecosystems and a microbial perspective for sustainable agricultural development.

Methods

The quantitative PCR and high-throughput sequencing technology were used to explore the variations of AOA community abundance and ecological characteristics among wheat growth stages and their environmental impact. Based on the loss of ammonia nitrogen concentration per unit time, the potential nitrification rate of wheat root soil was measured. Finally, based on the control experiment, this study further explored the response AOA community and nitrification rate to nitrogen addition.

Results

Both AOA abundance and nitrification rates were significantly influenced by seasonal changes. During the vegetative growth stage (VGSS), AOA abundance and the nitrification rate reached its peak, and during the reproductive growth stage (RGSS) fell to a low. The α-and β-diversity characteristics of AOA communities showed significant differences across seasons. with VGSS soils showing higher network connectivity and complexity compared to RGSS soils. These differences suggest that random processes primarily regulated community assembly during VGSS. Additionally, exogenous nitrogen addition significantly increased AOA abundance and nitrification rates, with the most pronounced effects observed in the high nitrogen group, indicating that nitrogen availability is a key factor influencing AOA activity and nitrification efficiency in farmland soils.

Conclusions

Our study provides new insights into the role of AOA in the farmland soil nitrogen cycle, and highlights the potential of microbial management strategies to facilitate nitrification and contribute to agricultural sustainability.