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
datawere obtained fromfifty pedons sampled at the Missouri Ozark Forest EcosystemProject (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) analysiswas applied to explain relationships between P concentrations
and environmental and soil properties. Total P concentration in the soils studied ranged from 15.6 to
410 mg kg−1 and the range of available P concentration was 0.29 to 30.6 mg kg−1. The CART analysis identified
variables, primarily soil attributes, explaining 48, 71, and 65% of the variability associatedwith 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.