The effects of grazing and oak tree removal on soil quality and fertility were examined for a blue oak woodland in northern California. Oak woodland/annual grasslands comprise an estimated 3 million hectares in California, and are used extensively for cattle grazing, providing approximately 75% of the forage produced on California's rangelands. Organic matter additions and nutrient cycling have enabled blue oaks to create islands of enhanced soil quality and fertility beneath the canopy. Analyses of both soil solution and solid-phase soil samples indicated that soil quality and fertility parameters decreased to levels similar to adjacent grassland levels within 5-21 years following tree removal. Additional research is underway to determine whether oak removal results in a similar response in soils formed from other parent materials (e.g., granite and sedimentary bedrock). Compared to oak tree removal, grazing appears to have had little impact on soil quality parameters at this study site. However, grazing impacts could be much greater if more intensive grazing practices were utilized on many rangelands. The kinetic analysis of the soils undergoing long-term laboratory incubation showed marked differences in the behavior of soil organic matter (SOM) pools in soils beneath oak canopies and adjacent grasslands. Soils from grass sites, including those adjacent to stumps, showed bi-phasic SOM pools characterized by labile (fast turnover) and resistant (slow turnover) C mineralization rates. Soils from under oak trees exhibited only one pool of readily mineralizable SOM characterized by a fast turnover rate. The large, labile SOM pool under oak trees demonstrates their importance in maintaining soil quality in these systems. This study suggests that conserving oaks as a component of these ecosystems enhances the soil quality and contributes to the long-term sustainability of California's rangelands. We also conclude that moderate intensity grazing has minimal affect on soil quality.