Rhizosphere remediation of saline-alkali soils by Helianthus tuberosus: Linking microbial-metabolite synergies to carbon sequestration

Saline-alkali soils (SAS) threaten global food security and climate resilience by degrading soil health and undermining carbon sequestration. While salt-tolerant crops offer nature-based solutions, their mechanisms of soil structure recovery and carbon stabilization remain unclear. This study across three typical Chinese SAS regions (Songnen, Hetao, and Jianghuai Plain) shows that cultivating Jerusalem artichoke (JA)-a high-value salt-tolerant crop-for 1-2 years drives SAS rehabilitation through rhizosphere engineering. JA improves aggregate stability (2.96-10.31-fold), reduces soil salinity (12.3-90.0 %), boosts soil organic carbon (SOC) stocks (9.21-12.78 Mg C ha^-1 yr^-1), and optimizes nitrogen cycling (NO₃/NH₄ decreased by 44.9-83.8 %). Key metabolites (e.g., trehalose 6-phosphate) mediate these improvements by selectively enriching key microbes identified via network and LEfSe analyses (Solirubrobacter, Sphingomonas, Nitrospira, Variovorax). These microbes drive region-specific carbon turnover through coordinated CAZyme activities: GH13 and CBM48 enhance microbial carbon use efficiency via labile carbon hydrolysis, GT51 promotes SOC accumulation through recalcitrant necromass production and aggregation, and CBM2/GH facilitates carbon accessibility, forming a degrade/rebuild cascade that integrates carbon retention with JA's adaptive growth. PLS-SEM analysis confirms that JA cultivation primarily enhances soil structure stability (total effect: +0.762) and SOC accumulation (+0.639) by stimulating a cohesive microbe-metabolite-enzyme network. This synergy directly improves soil structure, with Year 2 outperforming Year 1 as microbial functions shift from stress adaptation to nutrient cycling. JA thus balances agronomic productivity with ecological restoration, establishing a plant-soil feedback framework for sustainable SAS rehabilitation.