Grazing Relations — Abstract of Paper


Changes in Soil Quality Due to Grazing and Oak Tree Removal in California Blue Oak Woodlands
Trina J. Camping,¹ Randy A. Dahlgren,¹ William R. Horwath² and Kenneth W. Tate,¹


The effects of grazing and oak tree removal on soil quality and fertility were examined in a blue oak (Quercus douglasii) woodland in the northern Sierra Nevada foothills. Low to moderate grazing intensity has little affect on soil quality; however, oak tree removal resulted in a decrease in most soil quality parameters investigated (carbon, nitrogen, phosphorus, pH) within 5 to 15 years following tree removal. Following tree removal, total C and N pools in the 0-15 cm depth increment decreased by 10 to 20 percent after 5 years and 20 to 40 percent after 21 years. These changes were largest in the 0-5 cm soil depth, but did occur at a slower rate in the 5-15 cm depth. Because all of the soil quality parameters measured are directly related to soil organic matter quantity and/or nutrient cycling processes, removal of oak trees quickly results in a deterioration of soil quality by cutting off the major input of organic matter to the soil. Thus, oak tree removal in blue oak woodland ecosystems in the Sierra Nevada foothills leads to a rapid decline in soil quality and fertility.