Synergistic plant-fungal interactions under Phragmites australis - mangrove mixed growth regimes boost particulate organic carbon sequestration in estuarine wetlands

Abstract

Estuarine wetlands, as globally critical carbon sink systems, rely heavily on the dynamics of soil particulate organic carbon (POC) to regulate carbon cycling. However, the mechanisms underlying how plant-fungal synergies under mixed plant communities drive POC accumulation remain unclear. This study focuses on the Min River Estuary wetlands, comparing the effects of mangrove wetland, Phragmites australis wetland, and mixed P. australis-mangrove wetland on soil POC and carbon components in particulate organic matter (POM). Mixed communities exhibit higher total biomass than monocultures. Fungal community analysis demonstrated that the relative abundances of Roussoella, Geosmithia, and Entorrhiza in mixed wetlands were significantly higher than in monoculture habitats (p < 0.05), with Geosmithia showing a significant positive correlation with POC (p < 0.05). Annual mean POC content in mixed wetlands surpassed mangrove and P. australis monocultures by 29.31 % and 28.69 %, respectively. RDA analysis revealed that aboveground biomass (AGB), belowground biomass (BGB), Papiliotrema, and Phaeomyces were the primary factors driving variations in POC. Collectively, mixed plant communities enhance POC accumulation by promoting diverse litter inputs and fungal-driven lignin decomposition-stabilization pathways. These findings elucidates the synergistic plant-fungal interactions driving POC accumulation in estuarine wetlands under mixed plant communities, providing a theoretical foundation for enhancing coastal wetland carbon sequestration and refining predictions of carbon cycling under global change.