Short-term nitrogen enrichment alters microbial phosphorous limitation in Pinus taiwanensis forest soils

Soil microorganisms play pivotal roles in governing nutrient cycling, fertility maintenance, and carbon sequestration in terrestrial ecosystems. A three-year nitrogen enrichment experiment was conducted to investigate the consequences of nitrogen-induced stoichiometric imbalance on soil microbial communities in Pinus taiwanensis forests. Stoichiometric imbalance refers to a mismatch between the stoichiometry of soil nutrients and microbial biomass. Redundancy analysis (RDA) indicated that nitrogen enrichment predominantly correlates with shifts in the soil bacterial community, which are mainly associated with total soil carbon and available phosphorous. Changes in the soil microbial community were associated with the regulation of microbial biomass carbon and phosphorous. Fungal community variations were primarily influenced by increased nitrogen availability rather than soil acidification. Microbial communities influence nutrient restriction through dynamic adjustments to their structural composition. Additionally, a discernible relationship was identified between fungi and the carbon-to-nitrogen ratio of microbial biomass, as well as the carbon-to-phosphorous ratio of microbial biomass. We identified specific taxa from both Chloroflexi (bacteria) and Tremellomycetes (fungi) as biomarkers associated with specific particular nitrogen treatments. Chloroflexi establishes a specialized phosphorous-acquisition niche that not only supports its competitive survival in low-P soil environments but also facilitates its dominance in the microbial community. These biomarkers represent species with varying abundances that induce changes in microbial community structure. Notably, these taxa were identified as potential primary factors in microbial phosphorous limitation. The evidence, where vector A exceeds 45° , indicates that the soil is experiencing phosphorous limitation. Nitrogen enrichment did not exacerbate microbial carbon limitation but intensified phosphorous limitation, as evidenced by enzyme stoichiometry. These findings advance our understanding of how excess nitrogen alters soil microbial nutrient dynamics and community composition in subtropical forest ecosystems.