Understanding Soil Moisture Levels on Soledad Ridge, Santa Rosa Island, California during the Summer Months

Santa Rosa Island located off the coast of Santa Barbara County was grazed by non-native ungulates leaving the island stripped of vegetation topsoil layer. With the removal of ungulates, the National Park Service began restoring the Cloud Forest on Soledad Ridge. Soledad Ridge is said to have once been covered by large stands of island oaks (Quercus tometella) and other endemic and native plants. The unique leaf and structural morphology of such vegetation collects water from wind derived fog which serves as the main source of water for this unique ecosystem. In an effort to jump-start ecosystem vegetation recovery, a total of 12 two by ten-meter restoration plots under three restoration treatments were installed across four sites. Two sites are characterized as soil sites and two are characterized as bedrock sites. The restoration techniques and treatments include the installation of wattles for erosion control, shade cloth covered 1-inch mesh fences to harvest water from fog, short-term drip irrigation, and the establishment of native plants. This specific study focused on understanding if there is a significant difference in how much fog derived moisture is being absorbed under various restoration treatments, and at what depth in the soil is moisture the most intense. Data was collected using soil moisture probes and using the gravimetric soil moisture technique on soil samples. Based on a soil moisture index, probe results showed that soil moisture under the fog fence treatment was highest. Both soil probe and gravimetric readings showed that soil moisture is more intense at 10 centimeters than at five centimeters. This study aids in showcasing how and if soil moisture conditions are optimal for plant growth and ecosystem recovery