One reason restoration often fails is a lack of native plant establishment. Establishment failure can occur due to a lack of dispersal into the site, inappropriate abiotic conditions for plant survival, or biotic interactions that reduce germination rates or seedling survival. Understanding what is limiting establishment is critical for restoration success. Unfortunately, there has been little synthetic work to identify which restoration practices (e.g., direct seeding, weeding, irrigation) are most likely to improve plant establishment. Here we used a meta-analytical approach to determine what practices are most likely to enhance establishment success in grassland communities in California. We explored the impact of these practices on whole communities as well as on different functional groups (grass and forb). We categorized techniques by the constraint they addressed (dispersal, abiotic, or biotic) to determine which restoration practices are more likely to improve plant establishment. We found that addressing the dispersal filter is the best way to improve plant establishment regardless of the functional group. This suggests that most native plants targeted in restoration are seed limited. While we were able to identify restoration techniques that improve plant establishment, our synthesis revealed that there were insufficient numbers of studies and a lack of uniformity between treatments that hampered efforts to make broad conclusions. If we can expand research to more ecosystems, and use standardized treatments within each ecosystem, the restoration community could synthesize research more efficiently, which would inform our ultimate goal of increasing the success of restoration.

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In coastal California dune ecosystems protect coastal cities from damaging storms and provide habitat for native wildlife. Despite the economic and ecological importance of coastal dunes, habitat loss has continued and is predicted to accelerate with a changing climate. To combat the effects of climate change and ensure that coastal dunes will persist into the future, they need to be prioritized for conservation and restoration. However, for restoration to be successful, endemic plants, which are plant with specialized habitat requirements, need to be prioritized because they make up a significant portion of the biodiversity in California coastal dunes. Because endemic plants are rare and there is limited stock of plants available for transplant, we need to be more aggressive in using pilot studies. These can be used to evaluate the biotic and abiotic conditions that maximize growth and reproduction and to help guide effective reintroduction. To evaluate how exploratory pilot studies can enhance the restoration of rare and endemic plant species, we conducted a study restoring Lupinus nipomensis, a United States federally endangered species, on coastal dunes in San Luis Obispo County, California. We found that L. nipomensis had the highest seed production in plots that had a steep, north facing slope and were protected from herbivores. Our results suggest that restoration efforts should be focused on areas with these characteristics to maximize restoration success. Our pilot reintroduction of L. nipomensis highlights the importance of using pilot experiments to enhance reintroduction success and to quicken the recovery of coastal dune ecosystems.