Influence of Pinyon Pine Trees on Soil Chemical and Physical Properties

Abstract Accumulation of nutrients in the surface soil beneath mature pinyon pines ( Pinus edulis Engelm.) was compared to nutrient levels in adjacent shrub‐dominated areas. With the exception of Cu, concentrations of both macro‐ and micronutrients ranged from 2 to 20 times higher in the soil beneath 490‐year‐old trees than in adjacent areas where the length of biotic influence was presumed to be considerably less. Phosphorus concentrations beneath the trees averaged 132 ppm and suggested the presence of octocalcium phosphate. Significantly less clay was found beneath the pinyon trees than in the shrub‐dominated openings, an apparent result of eolian material accumulating beneath the pinyon canopy. Regression equations relating tree age to levels of macronutrients, B, conductivity, organic matter, and clay in the soil beneath the trees were highly significant (0.01 level); coefficients of determination ranged from 0.47 to 0.77.