The Use of Native Plants and Mycorrhizal Fungi for Slope Stabilization and Topsoil Management

Several field and greenhouse projects were undertaken to improve understanding of native plants and their association with arbuscular mycorrhizal fungi in a restoration context. At a site near Los Olivos, California, the erosion control benefits of two live mycorrhizal amendments and a sterile control were tested on a filled embankment. The native inoculum cultured from a nearby donor site outperformed a commercially available product in reducing soil erosion. The utility of applying of a commercial mycorrhizal inoculant was tested for use in restoring a cut slope lacking topsoil but no benefit was found. Some of the biophysical changes that occur when native topsoil is excavated and stockpiled were investigated. A general decline in soil quality from excavating and salvaging operations was noted, evident in the loss of soil aggregate stability, increased bulk density, lost soil organic matter, and a sharply reduced nutrient profile. Native species can benefit in subtle ways from the application of a cover crop once stockpiled soil has been redisturbed and re-applied for habitat restoration. These benefits would likely accrue over time and a cover cropping regime would need to be implemented with a carefully managed fertilization plan to replace nutrients lost from the initial excavation.