January 1, 2019.
Research on the Cloud Forest Restoration Project at Soledad Ridge, Santa Rosa Island in Channel Islands National Park, aims to understand the properties of soil water infiltration, specifically field‚Äêsaturated soil hydraulic conductivity (Kfs). Measuring the soil water infiltration rate allows us to calculate potential water reaching plant root systems, the amount of water remaining on the surface, and potential water runoff. The soil types on Soledad Ridge have different organic matter origins including: Island oak trees (Quercus tomentella), annual grasses (eg. Bromus spp., Avena spp), and coyote brush (Baccharis pilularis). In some areas historic non-native herbivore overgrazing resulted in erosion of upper organic layers, exposing large sections of bedrock. We hypothesized that the hydraulic conductivity will be lower in bedrock sections as compared to the other soil types present on site. We used a modified bottomless bucket method (Mirus 2012) consisting of a small bucket approximately 20 centimeters in diameter with the bottom removed. The bucket was secured to each of the soil types to make a watertight seal: bedrock required caulking; the other soil types required grooving and twisting into the ground. The amount of time required for one liter of water to infiltrate was measured which yielded the hydraulic conductivity (Kfs). We found that bedrock had the lowest infiltration rate of approximately 1 Kfs whereas the other soils had a rate of approximately 100 Kfs. These results support our hypothesis that bedrock hydraulic conductivity is significantly slower than infiltration of the other soil types. These results can be used to design suitable planting and irrigation treatments in future restoration efforts at the cloud forest.
Kathryn McEachern, Ken Niessen, Robyn Shea
California State University, Channel Islands (CSUCI)
The 2018 STEM Teacher and Researcher Program and this project have been made possible through support from Chevron (www.chevron.com), the National Marine Sanctuary Foundation (www.marinesanctuary.org), the National Science Foundation through the Robert Noyce Program under Grant #1836335 and 1340110, the California State University Office of the Chancellor, and California Polytechnic State University in partnership with California State University, Channel Islands. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the funders.