Co-occurrence networks dominated by rare and abundant fungal species influence the potential function of fungal communities in Eucalyptus urophylla plantations under successive planting

The successive planting of Eucalyptus urophylla significantly disturbs soil fungal community composition. However, little is known about how abundant and rare species, the main contributors to community composition, are affected by the above planting pattern. We aim to investigate the abundant and rare fungal taxa affected by the successive planting of E. urophylla and identify the driving factors affecting them. First-to-fourth generations of E. urophylla plantations and a broad-leaved forest were established in Guangxi State Daguishan Forest Farm in southern China. We used co-occurrence network analysis to identify key taxa and employed partial least squares path modeling to reveal the main driving force affecting them. Results showed that successive planting altered rare fungi in the soil. Compared with abundant species, rare species had a higher average degree and betweenness centrality, in which saprophytes occupy important nodes but some pathogenic fungi also exhibited a marked upward trend with increasing planting generations. Umbelopsis and Russula were symbiotrophs and decreased significantly with successive planting. The concentrations of total potassium (TK) and available boron in the soil, as well as pH, were important driving factors that directly affected the key taxa. Our results suggest that the successive planting of E. urophylla disturbed the primitive status of rare fungi. The function of the fungal community tended to change with the decrease in symbiotic fungi and increase in saprophytic and pathogenic fungi. Based on the above research, the sustainable management of Eucalyptus urophylla plantations should regulate soil pH and potassium content, reduce excessive soil disturbance, and retain harvest residues to restore the balance of fungal communities and alleviate successive planting obstacles.