Soil micro-food web interactions and rhizosphere priming effect

Abstract

The rhizosphere priming effect (RPE) is the stimulation or suppression of soil organic matter decomposition by living roots and associated rhizosphere organisms. The RPE is pivotal in regulating biogeochemical cycles in terrestrial ecosystems. However, biological mechanisms, especially soil micro-food web interactions, behind the RPE remain largely unknown. We quantified the RPE of soybean and cottonwood at three growth stages using a natural 13C tracer method, measured soil microbial and nematode community composition, and investigated their relations with the RPE. The magnitude of the RPE varied widely at different growth stages. Soybean produced a greater cumulative RPE than cottonwood. The plant species effect was also observed in the bacterial PLFA with higher values found in the soybean treatment. Mantel test analysis suggested that the variations in microbial community were closely related with the RPE, soil and plant characteristics. The nematode community affected the RPE indirectly through altering the structure of the microbial community. We demonstrated that the RPE was connected with interactions of soil micro-food webs. This connection indicates that soil micro-food web interactions in the rhizosphere may either regulate microbial turnover and/or microbial community composition, subsequently modulating the RPE.