Bedrock determines the elevational patterns of soil phosphorus pools in a subtropical karst forest

Soil phosphorus (P) is an important nutrient limiting plant productivity. The elevational pattern of soil P concentrations is widely used to indicate how P pools are affected by the climate. Despite previous research finding various patterns of soil P concentration across different elevations, little research has been conducted on how bedrock variation in an elevational transect affects P pools. In this study, we examined the elevational patterns of soil P pools (e.g., labile inorganic P (Pi) and organic P (Po), moderately labile Pi and Po, primary mineral P, and occluded P) in top-soils in an elevational transect with alternating bedrock types of clasolite and limestone in a subtropical karst forest. The results showed that concentrations of soil total P, labile Pi, primary P, and occluded P were significantly higher in limestone soils than clasolite soils, while there were no significant differences in labile Po, moderately labile Pi and Po concentrations between the two bedrocks. There were generally no significant linear elevational trends for soil P pools. Our results revealed that the bedrock type had a greater influence on soil P pools than climatic factors. Our study emphasizes the importance of using bedrock changes as a driving factor for the spatial distribution of soil phosphorus pools in mountainous ecosystems.