The Influence of Hydrogeomorphology, Soil Redox Conditions, and Salinity on the Spatial Zoning of Saltgrass, Salt Rush, and Cattails in Scotts Creek Marsh, Swanton Pacific Ranch, CA

Author

Mark D. Gormley, California Polytechnic State University, San Luis ObispoFollow

DOI: https://doi.org/10.15368/theses.2013.233
Available at: https://digitalcommons.calpoly.edu/theses/1167

Date of Award

12-2013

Degree Name

MS in Agriculture - Soil Science

College

College of Agriculture, Food, and Environmental Sciences

Advisor

Karen Vaughan

Advisor College

College of Agriculture, Food, and Environmental Sciences

Abstract

Scotts Creek Marsh (SCM) is a small coastal wetland ecosystem in Davenport, CA. The vegetation of SCM is dominated by three halophytic zones comprised of saltgrass, salt rush, cattails. The objectives of the study were (i) to investigate the variables that influence the zoning of the three dominant halophyte communities in SCM and (ii) to the test the effectiveness of Indicator of Reduction in Soil (IRIS) tubes to indicate the reduction of S. The study examined the following parameters from April 6 to July 21, 2013: (i) the HGM of Scotts Creek Marsh, (ii) soil oxidation and reduction (redox) conditions, (iii) salinity, and (iii) the effectiveness of Adobe Photoshop CS 5.1 (AP5) to analyze IRIS images. All three halophytes were well suited for anoxic, redox, and saline conditions by utilizing morphological adaptations (arenchyma, adventitious roots) to their root systems. The study concluded that the spatial zoning of the three dominate halophyte species within SCM was most likely due to slight differences in the water levels and salinity. The halophytes within SCM were zoned with saltgrass occupying the areas with the lowest water table and highest EC (26.98 dS/m). The cattails dominated the low average saline areas (9.60 dS/m) near the marsh channels with the highest water level. The salt rush zones had a mild EC level of 15.24 dS/m and intermediate water level. The IRIS tubes that were installed as indicators of both sulfur and iron reduction were effective. The tubes that were withdrawn after the closure of Scott’s Creek all had more than 30% reduction of the Fe³⁺ paint. The results from the IRIS study indicate that they are effective at recording the reduction of sulfur. The use of AP5 seemed to be an effective tool for analyzing IRIS images. The analyzed data from the study suggests that changes to the HGM of SCM could potentially alter the ecology of the marsh.