Differential patterns of dissolved organic matter-microbe interactions under consecutive nitrogen addition revealed by Energy-Diversity-Trait integrative Analysis in a Moso bamboo forest

Abstract Aims The interaction between dissolved organic matter (DOM) and microbial communities serves as a critical regulator of forest soil carbon (C) pool dynamics; however, the mechanistic drivers of these relationships under prolonged nitrogen (N) addition remain unclear. Methods Using a combination of fluorescence spectroscopy, high-throughput sequencing, and co-occurrence network analysis, we explored the responses of bacterial and fungal communities, along with their interactions with DOM to N addition. By applying the Energy-Diversity-Trait integrative Analysis (EDTiA) framework, we further elucidated the potential mechanisms shaping these interactions. Results Results showed that N addition significantly reduced soil dissolved organic carbon content and reshaped bacterial life-history strategies, notably suppressing copiotrophic bacterial taxa. Compared to fungi, bacterial communities exhibited greater sensitivity to N enrichment and displayed a tighter linkage with DOM traits. Network analysis indicated divergent response patterns in bacterial versus fungal interactions with DOM under N addition. The EDTiA framework further revealed that low-N addition weakened DOM-bacteria interactions, primarily mediated by alterations in DOM composition and bacterial life-history strategies. Conversely, high-N conditions strengthened DOM-fungi interactions, likely attributable to enhanced energy inputs, improved nutrient availability (particularly elevated nitrate levels), and increased microbial biomass. Conclusion These results underscore the central roles of energy and nutrient supply, DOM composition, and microbial life-history strategies in governing DOM-microbe interactions, offering novel insights into how N deposition shapes microbial mediation of soil carbon processes.