Nutrient Cycling in Managed and Unmanaged Oak

Abstract: The influence of oak trees and grazing on nutrient cycling in oak woodland-grass ecosystems was examined at the Sierra Foothill Range Field Station in the northern-Sierra Ne-vada foothills of California. Nutrient concentrations in ecosys-tem waterflows (precipitation, canopy throughfall, and soil solutions) were monitored in a non-managed natural area and in an adjacent grazed area. Grazing increased soil solution concen-trations of chloride (Cl) and sodium (Na), but had no effect on major nutrient levels. When comparing between oak and non-oak sites, the oak sites had enhanced soil solution concentrations of Ca, Mg, K, SO4 and PO4, and decreased levels of Na. Soil solution pH beneath the oak canopy was 0.5-1.0 units greater than in adjacent grasslands, and appears to be due to neutraliza-tion of rainfall acidity by the oak canopy and enhanced base cation cycling by the oak