Keeping Tabs on Quercus boyntonii

Through much of the year 2020, conservation horticulturalists teamed up to collect and document one of the world’s rarest species of oaks, Quercus boyntonii, the Alabama sandstone oak. The species is known to be extant in six counties in central and northeastern Alabama (USA), and is listed as Critically Endangered by the International Union for the Conservation of Nature. The effort was led by Tracy Cook, Director of the Department of Conservation at the Huntsville Botanical Garden. Her primary collaborator on the expedition was Patrick Thompson, Curator at Auburn University’s Davis Arboretum and Coordinator of the Alabama Plant Conservation Alliance (APCA). The effort was made possible by a Tree Gene Conservation grant funded by the Association of Public Gardens of America and the US Forest Service. The APCA had spent years developing landowner contacts and working to increase awareness surrounding this cryptic species of dwarf oak, generating many leads for the team to pursue in their effort to find trees with enough acorns to collect for preservation in living collections.

Due to the fact that the entire wild population of the species was reported to be only a few hundred individuals, from perhaps 10 elemental occurrences, the team decided to collect more than 30 fields of data on every individual Q. boyntonii they were able to locate. The idea was that a detailed snapshot of the species would provide important baseline information to build on as the team works to illuminate the natural history and basic biology of this little-known Alabama endemic plant. The team began by evaluating outlying occurrences at the southern extent of the range. Plants discovered by the APCA in Autauga County, if verified, will be a new county record for the species, expanding its known range to seven Alabama counties. Proceeding north, the team was able to locate several heavily fruited individuals along the ridge of Double Oak Mountain in Shelby County, on a mixture of state and private lands.

The heart of the range of Q. boyntonii is in Birmingham, the largest city in the state of Alabama. There is a thriving subpopulation to the south that was well documented by this effort, and two, perhaps three, viable populations north of Birmingham have been recognized. The city and its outlying towns and suburbs have spread across what could have been the densest parts of the species genepool, suggesting that the development of Birmingham is the primary reason that the species is critically endangered. This project was able to document five remnant populations within the Birmingham area previously unknown to the Alabama Natural Heritage Program. Unfortunately none of these plants produced enough acorns to collect this year.

An outlying occurrence north of Birmingham on the Cumberland Plateau ended up having a surprising amount of Q. boyntonii, nearly 70 plants observed in just a few hours of walking the privately owned property. The landowners were enthused and look forward to having the team return for a full census of the site. Though there were some exposed rocks, many of the trees were found on sloping, grassy, savannah-like habitat where they extended right down into the flood zone of the Black Warrior River. The team was able to count 496 specimens, leaving approximately 1/3 of the known range to be surveyed in future census efforts. There were 667 acorns collected from 17 maternal lines, which were distributed to 11 public gardens in the Eastern US.

The team also mapped and photographed a series of presumed hybrids that occur with Q. boyntonii and Q. margarettae, Q. montana, Q. stellata, and Q. alba. The completion of the survey and germplasm collection will hopefully take place in 2022. The completion of the survey work will allow for analysis of the frequency of growth forms and for a truer understanding of the number of occurrences and the total population of the species. Details of the project available at: http://www.auburn.edu/cosam/arboretum/treegenepartnership/index.htm