Date of Award


Degree Name

MS in Agriculture - Soil Science


Natural Resources Management


Dr. Karen L Vaughan


Wetlands serve an important ecological and functional role in the environment. In order to protect wetlands from degradation, the determination of wetland hydrology, hydrophytic vegetation, and hydric soils is necessary. Soils formed from serpentine parent material on hillside slump blocks do not meet any of the current morphological Field Indicators of Hydric Soils. Although these areas seem to be wetlands based on wetland hydrology and hydrophytic vegetation, there is no approved hydric soil indicator that includes the properties exhibited by serpentinitic soils on these landscapes. The objectives of this research were: (1) to examine soil chemical, physical, and morphological properties to determine if they meet the criteria for hydric soils; and (2) to develop a new test Field Indicator of Hydric Soil for use in soils formed in serpentinitic parent materials along the Central Coast of California. Two research sites in Poly Canyon, north of California Polytechnic State University in San Luis Obispo, were instrumented with Indicator of Reduction in Soil (IRIS) tubes over a three month period to measure the amount of Fe reduction in the soil profiles to a depth of 50 cm. The results of the IRIS tube analyses displayed anaerobic conditions persisting for longer than 14 days during the growing season; therefore, these soils are in fact hydric. The development of a new test Field Indicator of Hydric Soil is necessary. Preliminarily, the following is proposed as a new test indicator: soils formed in serpentine parent material occurring on a slump block landforms with a layer at least 10 cm (4 in) thick, no chroma color with a value of 2 or less, and few or less concentrations. The layer is entirely within 30 cm (12 in) of the soil surface. Further research to test this new field indicator includes an additional research site and a year of supplementary data.