Phosphorus is an important nutrient limiting forest growth in many parts of world, and soil P forms and concentrations may be associated with a host of soil and environmental attributes in a complex soil landscape. The objective of this study was to identify key environmental and soil properties influencing total and available soil P concentrations in a mixed oak (Quercus L.)–hickory (Carya Nutt.) forest ecosystem. Soil samples and soil characterization data were obtained from fifty pedons sampled at the Missouri Ozark Forest Ecosystem Project (MOFEP) located in south-central Missouri, USA. Additional soil chemical analyses were conducted to measure total P, available P (Mehlich-3 P and Bray-1 P), and citrate bicarbonate dithionite (CBD) extractable Fe, Al, and Mn content. Classification and regression tree (CART) analysis was applied to explain relationships between P concentrations and environmental and soil properties. Total P concentration in the soils studied ranged from 15.6 to 410mgkg−1 and the range of available P concentration was 0.29 to 30.6mgkg−1. The CART analysis identified variables, primarily soil attributes, explaining 48, 71, and 65% of the variability associated with total P, Mehlich-3 P, and Bray-1 P concentrations, respectively. Extractable Mn was the most important explanatory variable in all CART models (explaining 28–33% of soil P variation). The CART analysis provided a concise framework for coupling soil and environmental variables to understand and identify locations within a complex soil landscape that may be susceptible for nutrient depletion. Furthermore, findings of this research highlight a need to more thoroughly evaluate relationships between Mn and P forms and concentrations in soil.