Dissolved organic carbon (DOC) originates from leaching of the canopy and from incomplete decomposition of organic matter. Oak trees are known to contain relatively high concentrations of phenolic compounds contributing to formation of dissociated organic acids (organic anions). Concentrations of DOC are approximately 4 times greater in soil horizons beneath the oak canopy than in the adjacent grassland soils (Fig. 17). Following oak removal, DOC concentrations were significantly attenuated in all soil horizons.