Augmenting the smallest California endangered Dudleya brevifolia population

Stacy Anderson, Joe Davitt, Katie Heineman, David Hogan, Joyce Maschinski, and Tobin Weatherson, San Diego Zoo Global

Declining small populations may be supported through augmentation. To aid the smallest of five populations of the tiny endangered succulent, Dudleya brevifolia, The Chaparral Lands Conservancy approached the San Diego Zoo Global Plant Conservation team to augment the smallest population located on delicate sandstone bluffs of the Torrey Pines State Reserve Extension in Del Mar. On January 19, 2017, we germinated seed and grew plants in our nursery to learn about propagation needs. On January 4, 2019, we introduced 46 corms into two predesignated transect plots on two areas near the small extant population. Prior to planting, we cleaned each corm of potting soil, measured its length, assigned a unique id, and randomly designated it to a plot. On the installation day, we drilled holes in the sandstone to accommodate the corms, backfilled each with native soil, and watered. We noted the location of each introduced corm with a small nail and recorded x,y coordinates and GPS location using a sub-meter GPS. Later we buried 23 mm HDX pit tags next to the corms to ensure long-term location of each individual. Following installation, we monitored the status of each corm every two weeks. Thus far, we have noted aboveground growth of 8 individuals. However, we cannot determine if the corms are actively growing underground. We will continue to monitor the phenology of the corms this spring though it is possible that introduced corms are establishing underground and will not initiate aboveground growth until next spring.