Grassland restoration strategies for sandy soils under drought conditions: lessons learned from a seeding trial in Northern California

California contains some of the most geographically complex patterns of biodiversity on Earth, but much of that diversity has been lost since European settlement. California grasslands, for example, were once dominated by diverse native perennial grasses, geophytes, and annual forbs. Today, these grasslands are largely dominated by non-native, invasive, annual plant species. Detailed quantitative records of California grasslands prior to European colonization do not exist, and many grassland areas have likely been so altered that they may no longer support their original plant communities. Consequently, developing restoration plans that can both restore native grasslands and reduce non-native species pressure is challenging. One major challenge is restoring riparian grassland vegetation along drainages impacted by historical hydraulic mining. In 2015, we implemented a 2 x 2 factorial experimental design to assess survival and growth of eight native grasses and forbs at the Abbott Lake restoration site in Northern California. Approximately seven miles south of Yuba City in Sutter County, California, Abbott Lake was acquired by the California Department of Fish and Wildlife in 1982, and since acquisition, re-establishment of native riparian habitat that was present prior to degradation has been unsuccessful. Vegetation sampling was conducted in May 2015, and minimal seedling survival of the eight selected species was observed. Low survivorship results could be attributed to a combination of unseasonably warm temperatures, low precipitation, soil conditions, predation or other extraneous factors. This thesis looks at potential causes for low survivorship and provides recommendations for future grassland restoration projects specifically in sandy soils.