Ecological strategies govern fungal performance on soil carbon cycling in agroecosystems

Fungi are essential to maintaining ecosystem functions; fungal functional traits are impacted simultaneously by long‐term ecological interplay. However, how fungal types with different ecological strategies mediate functional traits remain poorly understood.

Here, we examined the role of ecotypes (specialists, opportunists or generalists) in shaping fungal community structure and function traits by employing a network of four long‐term (>10 years) nitrogen (N) gradient experiments across distinct regions with contrasting soil fertility. By combining amplicon sequencing and metagenomics, we evaluated the functional guilds and metabolic traits of these distinct ecotypes and determined the fungal carbon (C) mineralization rate to evaluate their contribution to carbon cycling.

The results showed that the overall abundance of fungi increased with increasing soil fertility, while the alpha diversity decreased and the ecological niche of fungi narrowed. Critically, specialists and opportunists exhibited different performances in the community, namely, the relative abundance of specialists increased, while that of opportunists decreased with increasing soil fertility. Specialists characterized by high‐energy metabolism and respiration became enriched in high‐fertility soils, which favours the dominance of saprotrophic fungi following N addition. Such community shift drives functionality alteration, for example, the diversity of carbohydrate metabolism and the capacity for cellulose degradation increased. A key saprotrophic specialist, Mortierella elongata , was significantly enriched in high‐fertility soils. Opportunists were suppressed by specialists in high‐fertility soils, whereas in low‐fertility soils their abundance increased and pathogen proliferation was promoted, particularly in N enrichment. These shifts showed no correlation with cellulose mineralization; yet, as predicted, was accompanied by enhanced amino acid decomposition. By comparison, generalists with low abundance remain stable across all soils.

Synthesis and applications . Our study highlights the dynamics of organic carbon and eventually soil fertility that fungi change with different ecological strategies, advancing a mechanistic understanding of how fungal communities maintain and modulate soil fertility. Utilizing key microbial traits as predictors significantly improves the assessment of agroecosystem services. Integrating the interplay of microbial functional and ecological attributes into models will enable more reliable forecasts of ecosystem sustainability.