Microbial processes controlling P availability in forest spodosols as affected by soil depth and soil properties

► We quantify the stocks of available P through microbial processes. ► We assess the relative contributions of surface and deep soil layers to these stocks. ► Microbial P and mineralized organic P decrease with increasing soil depth. ► The role of the deep soil layers (30-120 cm) can however be significant. ► The contributions of the different soil layers depend on several soil properties.