Elevation-dependent shifts in soil phosphorus forms and phosphorus-solubilizing microbial diversity suggest enhanced bioavailable phosphorus cycling with rising temperatures

Phosphorus is a crucial nutrient for plant growth, primarily found as insoluble phosphates in soil. The impact of climate change on the phosphorus cycle, particularly through geochemical cycling in forest soils, is underexplored. To address this gap, we investigated soil phosphorus distribution across five elevation gradients in different forest types using the modified Hedley fractionation method and high-throughput sequencing to assess phosphorus-solubilizing microorganisms (PSMs). Our study included evergreen broadleaf forest, coniferous and broadleaf mixed forest, coniferous forest, subalpine dwarf forest, and alpine meadow. We observed that with increasing elevation, organic phosphorus forms such as NaOH-Po and HCl-Po significantly increased, while H2O-Po and NaHCO3-Po varied, peaking in specific forest types. The proportion of labile phosphorus decreased with elevation, whereas stable phosphorus increased. Soil PSM diversity was highest in lower elevations and declined with altitude, with significant shifts in dominant PSM groups across vegetation types. PSMs analysis revealed correlations between specific phosphorus forms and microbial taxa, indicating that elevation and vegetation type influence PSM diversity and phosphorus form distribution. The differences in soil conditions between low and high elevations present distinct characteristics: rapid mineral weathering and organic matter decomposition occur at lower elevations, while higher elevations exhibit higher total phosphorus content but a lower proportion of labile phosphorus. These distinctions open avenues for future research on adaptive strategies for phosphorus management in agriculture and forestry across different altitudes. These findings suggest that rising temperatures may enhance PSM diversity, potentially increasing the proportion of bioavailable phosphorus and accelerating its cycle in forest ecosystems.