Effects of headwater wetland restoration on the demography, fecundity and ecology of the U.S. federally threatened white fringeless orchid (Platanthera integrilabia) in the Cumberland Plateau of Kentucky

Wetland habitats represent a critical component of biodiversity hotspots that support numerous rare species, including terrestrial orchids. In North America, over half of all terrestrial orchids are found in wetlands, more than a quarter of which are now threatened with extinction (G1–G3). This concerning trend is exacerbated by a lack of information on effective restoration strategies aimed at orchids and other species that inhabit these areas. The white fringeless orchid, Platanthera integrilabia (Correll) Luer, the subject of this study, is restricted to mostly shaded wetland habitats along the Cumberland Plateau of the Appalachian Mountains and has suffered widespread declines due to habitat destruction and hydrologic alterations leading to its U.S. Federal listing in 2016. During an 11-year period, (2009–2020), the effects of canopy thinning and hydrology modification (e.g., debris dam installation) were carried out in Kentucky to improve fecundity and viability in this species. Long-term monitoring revealed increased inundation rates, soil saturation, orchid viability, and enhanced floristic diversity. After 2–4 years post management, flowering increased by over 1000%, coinciding with higher fruit production. Although herbivory by white-tailed deer (Odocoileus virginianus) was widespread and notable (~ 50% of orchids affected), the percentage of aborted flowers declined, resulting in higher overall fruit set and seed production at the restored sites. Our results argue in support of adopting active habitat management as a conservation tool for P. integrilabia and other terrestrial orchids threatened with extinction.