Conflicting short and long-term management goals: Fire effects in endangered golden-cheeked warbler (Setophaga chrysoparia) habitat

Decades of fire suppression have significantly altered the vegetation structure and composition of savannas, woodlands, and forests. The presence of endangered species and other species of conservation concern in these fire-suppressed systems makes re-introducing fire more challenging. In oak-juniper woodlands of central Texas, we are presented with the challenge of re-introducing fire to attempt to increase oak regeneration, while simultaneously not substantially altering the vegetation structure and composition of the burned areas to avoid degrading habitat that is currently occupied by an endangered species, the golden-cheeked warbler (Setophaga chrysoparia). This bird breeds in Texas red oak (Quercus buckleyi) and Ashe juniper (Juniperus ashei) woodlands with an average combined canopy cover greater than 70 percent. To better understand the effects of fire on golden-cheeked warbler habitat, we examined the effects of four different wildfires on canopy cover and on the abundance and sizes of hardwoods and of Ashe juniper. Burned sites differed in fire frequency, fire seasonality, and time since fire. Burned sites had fewer Ashe juniper seedlings, saplings, and mature trees. Texas red oak and other hardwood trees and saplings sprouted after fire, but effects on hardwood seedlings were mixed. In the short-term, burned areas retained enough canopy cover to maintain golden-cheeked warbler habitat, but in the long-term, if oak regeneration failure continues in fire suppressed areas, these woodlands will likely become Ashe juniper woodlands and no longer provide quality habitat. It may be that more intense and severe fires are needed to sufficiently increase light availability and hence oak seedling abundance. We propose that pre-settlement vegetation was a fire-driven shifting mosaic of oak-savanna, shrubland, and oak-juniper woodland. Savanna and shrubland may mature into oak-juniper woodland under fire suppression, and more intense fires in oak juniper woodland may result in savanna or shrubland. If this proposition is correct, permanent designation of endangered species habitats to specific sites may be unattainable, as the suitability of habitat is dynamic and dependent on the natural fire cycle. We expect that conflicts between short and long-term management goals will increase in the future as stressors such as fire suppression, invasive species, and climate change continue to interact and drive novel plant and animal community dynamics.