Adaptation to fire in the rare Appalachian forest herb Xerophyllum asphodeloides and its implications for forest conservation and management

We conducted an extensive study of the role and effects of disturbance by fire on the population biology of turkeybeard (Xerophyllum asphodeloides (L.) Nutt., Melanthiaceae), a rare forest herb occurring in the southern Appalachian Mountains. Long term monitoring data analyses showed that turkeybeard is a long-lived, infrequently flowering perennial with high survival and rapid resprouting ability following fire. Disturbance effects on fruit/seed production were evaluated via a controlled, fire and canopy alteration ‘pulse’ experiment. Population-level flowering and inflorescence production rates increased 60-280% in the 2^nd and 3^rd post-treatment growing seasons. Treated plants had significantly greater fruit/seed production than controls. Relative isolation from other flowering plants had no significant effect on fruit and seed production. Additionally, total seed production per plant increased with floral display size. Population surveys and pollination biology experiments conducted over multiple flowering seasons showed that flowering was low in undisturbed forest and that the species possessed an early stigmatic self-incompatibility system with outcrossing needed for good seed set. These factors combined to subject populations to possible Allee effects in most years likely due to pollinator limitation. Disturbance by fire released plants from these limitations by inducing mass flowering and altering the forest habitat, thereby increasing pollinator activity and thus facilitating outcrossing and seed set. Our study revealed turkeybeard to be one of the few definitively fire-adapted forest understory herbs in the eastern United States. These findings are valuable not only as a major contribution to the understanding of disturbance regimes in Appalachian forests, but also for their implications for improving ecologically based conservation and management of these lands.