Plant invasion mediates the regulation of topsoil organic carbon sequestration by the fungal community in coastal wetlands

Spartina alterniflora, which is native to the Atlantic coast, has extensively invaded mangroves/marshes and hence seriously altered coastal soil organic carbon (SOC) sequestration along the Pacific coast. Fungi are directly engaged in the SOC cycle, but how the fungal community impacts coastal carbon sequestration in response to S. alterniflora invasion remains unclear. We explored the fungal community shifts in relation to SOC changes by comparing 6 pairs of independent sites (i.e., dominant native plants vs. S. alterniflora) along a 2,500 km coastal transect in southeastern China. Our results showed that the invasion reduced the fungal diversity and shifted the assemblage processes of the abundant subcommunity, not the rare subcommunity, from determinism (0.409) to stochasticity (0.556). The invasion decreased network topological properties (e.g., network size, centrality, natural connectivity, etc.), cohesion, robustness, and the relative abundance of keystone taxa but increased the vulnerability of the fungal community. Importantly, the Shannon index, total cohesion and keystone taxa of the fungal community were significantly positively correlated with SOC concentration, SOC storage and recalcitrant organic carbon (ROC) but not with labile organic carbon (LOC). The structural equation model further showed that the fungal community diversity, complexity and keystone taxa directly regulated SOC storage under S. alterniflora invasion. Overall, we provide new insights into fungal community shifts and cooccurrence patterns under S. alterniflora invasion, helping us better understand the impact of invasion on SOC cycling and its microbial mechanisms, which will benefit future restoration and optimal coastal management.