Elevated CO 2 amplifies contrasting cultivar‐specific plant–soil feedbacks mediated by soil biota

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Abstract
Atmospheric carbon dioxide enrichment (eCO 2 ) stimulates crop growth, and the fertilization effect can translate into sustained plant performance through soil biota‐mediated plant–soil feedbacks (PSFs). However, how cultivar‐specific responses to eCO 2 shape soil biotic legacies and determine the direction of PSFs remains poorly understood. Here, we combined a long‐term rice free‐air CO 2 enrichment (FACE) with a greenhouse PSF experiment to test whether weakly and strongly CO 2 ‐responsive cultivars develop contrasting PSFs, using soil inocula collected from FACE plots with contrasting CO 2 treatments and rice cultivars. The results showed that eCO 2 amplified cultivar‐specific PSFs, as reflected by negative PSFs in the strongly responsive cultivar and positive PSFs in the weakly responsive cultivar. Specifically, the strongly responsive cultivar exhibited a 20% reduction in biomass when grown with its own eCO 2 ‐conditioned soil, which was associated with increased herbivorous nematode abundance (35%). Moreover, soil biota‐mediated feedbacks altered cultivar‐specific growth–defence allocation under eCO 2 . The strongly responsive cultivar showed a growth–defence trade‐off, with increased phenolic concentrations occurring at the expense of biomass production, whereas the weakly responsive cultivar exhibited a synergistic enhancement of both biomass (21.4%) and phenolic concentrations (33.9%). Synthesis . Our study suggests that sustaining crop performance under future CO 2 scenarios requires cultivars that coordinate growth, defence and beneficial soil biotic interactions. Integrating cultivar selection with soil biota management therefore offers a promising strategy for sustaining crop production, soil health and agroecosystem resilience under future global change.
Funding Information
  • National Natural Science Foundation of China (32471611)
  • National Natural Science Foundation of China (31870423)

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