Fungal Communities Respond to Long-Term CO2 Elevation by Community Reassembly

摘要

Fungal communities play a major role as decomposers in the Earth's ecosystems. Their community-level responses to elevated CO_(2) (eCO_(2)), one of the major global change factors impacting ecosystems, are not well understood. Using 28S rRNA gene amplicon sequencing and co-occurrence ecological network approaches, we analyzed the response of soil fungal communities in the BioCON (biodiversity, CO_(2), and N deposition) experimental site in Minnesota, USA, in which a grassland ecosystem has been exposed to eCO_(2) for 12 years. Long-term eCO_(2) did not significantly change the overall fungal community structure and species richness, but significantly increased community evenness and diversity. The relative abundances of 119 operational taxonomic units (OTU; ～27% of the total captured sequences) were changed significantly. Significantly changed OTU under eCO_(2) were associated with decreased overall relative abundance of Ascomycota, but increased relative abundance of Basidiomycota. Co-occurrence ecological network analysis indicated that eCO_(2) increased fungal community network complexity, as evidenced by higher intermodular and intramodular connectivity and shorter geodesic distance. In contrast, decreased connections for dominant fungal species were observed in the eCO_(2) network. Community reassembly of unrelated fungal species into highly connected dense modules was observed. Such changes in the co-occurrence network topology were significantly associated with altered soil and plant properties under eCO_(2), especially with increased plant biomass and NH_(4)~(+) availability. This study provided novel insights into how eCO_(2) shapes soil fungal communities in grassland ecosystems.