#47

Drill-seeding Blue Oak Acorns is a New Method for Restoration in California’s Rangelands.

Alex Palmerlee, Far View Ranch

Carrie Wendt, Point Blue Conservation Science and Truman Young, University of California at Davis

In both cleared and existing blue oak woodlands, there is a lack of new oak recruitment. Problems of this scale require restoration solutions that are cost-effective and scalable. Existing restoration techniques use a litany of interventions (irrigation, caging, tree tubes, weed control) to ensure high survival per individual at a high price per survivor.

We tested the application of drill-seeding to “farm” oaks in rangelands with a low-tech slip-plow attachment. In two consecutive years we planted blue oak acorns under varying conditions, combining drill-seeding with cattle grazing, shade, and herbicide in a paired nested block study.

Our data suggest that drill-seeding large-seeded species may be a viable restoration technique under multiple conditions. After a year and a half, seedlings are at 6% survival with no post-planting interventions. The lack of costly interventions means that even at low percentages, survival is still very cost-effective. Calculated as a factor of equipment and labor time required to collect, treat, store, and plant acorns, the cost per surviving seedling was under $3.

Current restoration challenges, including those posed by climate change, demand that we develop more cost-effective planting techniques that can be applied on thousands of acres per year. Drill-seeding acorns, surpassing recruitment limitations by mass-seeding, may be a valuable addition to the restoration tool box.