Agave palmeri restoration: salvage and transplantation of population structure

Agave palmeri (Palmer’s agave) is a long-lived, monocarpic, perennial succulent which provides a critical flower nectar food source for the threatened species, Leptonycteris curasoae (lesser long-nosed bat) among other animals. Agave palmeri flower only once after approximately 25 years. To support the demography needed to have some plants flowering every year, wild populations of A. palmeri must be conserved and mining, construction, and recreational impacts must be mitigated. Collecting, storing, and transplanting wild plants was tested as a potential method for restoring and maintaining A. palmeri populations. In January 2009, 387 wild plants were collected, roughly half the plants were potted in field soil, and the remainder were placed in pots without soil (bare-root) and covered with burlap cloth. During 6-months storage, 1% of plants potted in field soil died while 31% of bare-root plants died. In July 2009, a denuded and scarified field plot was planted with the surviving 277 A. palmeri individuals. Plants received one of three water treatments: a 90-day slow-release gel irrigation supplement, 8 L (2 gal) of water, or no water or gel. Three years after transplanting, survivorship was assessed. The watering treatments had no significant effect on survivorship. The number of green leaves at the time of collection was the most important factor in predicting if the plants lived, died, or survived to flower before dying. Mortality is concentrated in the smallest and largest plants. Transplanting appears to be a viable method of returning diverse size classes of A. palmeri to disturbed sites.