Linkage between plant nitrogen preference and rhizosphere effects on soil nitrogen transformation reveals a plant resource adaptive strategies in nitrogen-limited soils

Abstract

Background and aims

Plant roots can induced changes in soil nitrogen (N) transformation, which is critical for plant N utilization in N-limited ecosystems. However, the linkage between plant N preference and the rhizosphere effects on soil N transformation is rarely explored.

Methods

We determined the relationship between plant N preference (¹⁵N labeling) and the rhizosphere effects on soil net ammonification/nitrification rates of three dominant shrub species (Artemisia ordosica, Salix psammophila, and Caragana korshinskii) in the Mu Us Desert, as well as root traits, rhizosphere and bulk soil microbiomes, functional genes and enzyme activities.

Results

S. psammophila and C. korshinskii with preference for NO₃⁻ had higher rhizosphere nitrification rates, while A. ordosica with preference for NH₄⁺ had higher rhizosphere ammonification rates. The plant N preference was also positively linked to the rhizosphere effects on soil N transformation, indicating that rhizosphere process provided positive feedback to plant N demands. Furthermore, root exudation rates and morphological traits explained the interspecific variations in rhizosphere effects on net ammonification and nitrification rates, respectively. The rhizosphere nifH gene copies and nitrogenase activity contributed to the increasing rhizosphere effect on ammonification rates, while rhizosphere ammonia-oxidizing archaea gene abundance was responsible for the rhizosphere effect on soil net nitrification rates.

Conclusion

We conclude that the linkage between plant N preference and rhizosphere effects on N transformation is driven by specific rhizosphere physical, physiological and microbial environments. This positive plant-soil feedback may promote species establishment in N-limited soils, which is insightful for understanding plant adaption from a rhizosphere perspective.