Using Dynamic Soil Property Project in Soil Survey to Assess Soil Change and Degredation.

Soil survey organizes the landscape into units with common soil properties, characteristics and classification. An implicit understanding in soil survey, is that these units have a common reference or potential set of soil properties.  These inherent properties, determined by soil forming factors, are augmented and modified by land used and management.  Traditionally, in the U.S., soil survey information is delivered with the dominant use of the landscape in mind.  Current enhancement of soil survey includes documenting dynamic soil properties and soil change due to ecosystem management. Ecological sites are a concept used to describe ‘kinds of land’ that have common potential kinds and amounts of vegetation and characteristic response to disturbance. In intensively managed (agronomic) systems, inputs (e.g. energy, fertilizer, irrigation water) can confound and homogenize vegetation indicators. In these situations, ecological site concepts, as constructed through state and transition models, can be differentiated based upon levels of soil function (indicated by dynamic soil properties) that occur as a result of the management (disturbance).  Reference conditions represent the highest function that can be maintained under desired land use systems.  Soil degradation can be inferred as deviation from reference conditions. We will examine projects conducted using this framework and compare expected and observed soil properties under various land management systems.  The variability of indicators of soil conditions, such as bulk density, aggregate stability and soil organic carbon will be discussed.  Results indicate that soil specific benchmarks (reference levels) are needed in order to interpret the status of current soil observations.