Soil quality and health - Some applications to ecosystem health and sustainability

Sustainability of forest and rangeland ecosystems is intricately linked wit h healthy and productive soils. Soils vary widely in their quality. Their h ealth is a condition of the soil relative to their inherent quality and abi lity to perform vital soil and ecosystem functions. Soils in Pacific Northw est forest and rangeland ecosystems are particularly heterogeneous. For exa mple, selected soils from six Ecoregions, have organic carbon contents that range from about 40,000 to more than 800,000 kg/ha. Total nitrogen content ranges from less than 2,000 to more than 50,000 kg/ha. There is a close relationship between soil quality and health and ecosystem quality and health. Ecosystem stresses can be increased by management acti vities that compact soils and alter soil moisture and nutrient status and p rocesses. Forest health in Inland Western forests is intricately linked wit h carbon and nutrient cycling. A high percentage of soil organisms make the ir home in the soil and play a critical role in the functions of ecosystems . Alteration of soil physical and nutrient conditions can alter the inciden ce of soil borne diseases which, in turn, affect the health of ecosystems. Specific quantitative soil standards, or thresholds, are needed to determin e detrimental conditions. The National Forests have established a variety o f measures of detrimental conditions. A variety of physical measures, such as bulk density changes, displacement and erosion, and detrimental burn con ditions are emphasized. Soils vary widely in their resiliency, or ability to rebound from impacts. A model of soil resiliency adopted from Szabolcs (1994), includes physical, chemical and biological buffering and pedological and anthropological soil fluxes. Several soils from six Pacific Northwest Ecoregions are rated for their resiliency. Criteria for chemical, biological and physical buffering is included.