Peatlands, vital global carbon sinks dominated by Sphagnum , are increasingly threatened by water table decline (WTD) and nitrogen-phosphorus (N-P) enrichment. Sphagnum relies on complex microbial communities for ecosystem functions, but the combined impacts of these stressors on its physiology, soil biogeochemistry, and microbiome dynamics were poorly understood. In this study, a controlled experiment combining WTD and N-P addition was conducted to investigate how these perturbations alter plant–soil–microbe interactions. Under WTD, soil carbon to nitrogen (C/N) and carbon to phosphorus (C/P) ratios increased while the N/P ratio decreased, indicating altered stoichiometric characteristics. Soil NH 4 + concentrations increased whereas NO 3 − decreased. Soil microbial α-diversity declined, and community assembly analyses further indicated that dispersal limitation played a dominant role in shaping community composition. In contrast, the endophytic microbiome of Sphagnum palustre maintained relatively high network complexity, reflected by increased edge number and average degree. N–P addition increased soil total nitrogen (TN) and total phosphorus (TP) contents and partially restored soil microbial diversity, but reduced the complexity of endophytic microbial networks. Functional gene analysis showed that WTD increased the abundance of several key genes associated with carbon and nitrogen cycling (e.g., nir K, nir S), whereas N–P addition suppressed a substantial subset of these genes. Co-occurrence network analysis revealed keystone taxa shifts and links between microbial network stability, modularity, and capitulum moisture and stoichiometry (e.g., TC/TP, TN/TP). Our findings highlight a stoichiometry-driven mechanism by which hydrological and nutrient perturbations reshape plant–microbe interactions, providing new insight into peatland resilience under global change. • Water table decline is the primary driver of microbial diversity and community composition. • Water table decline triggers N-P limitation by altering stoichiometric ratios. • Compared to soil microbial communities, endophytes exhibit a more stable network structure. • Nitrogen-phosphorus addition mitigates hydrological stress effects on soil microbial communities. • Nitrogen-phosphorus addition reduces the stability of endophytic microbial networks.
Yang et al. (Fri,) studied this question.