The smell of smoke is in the air. On Sunday, February 17, 2013, the Refuge burned the first of three 100-acre plots in Golden-cheeked Warbler habitat as part of a designed experiment. The Refuge manages approximately 14,000 acres for Golden-cheeked Warblers. Why are we burning these three 100-acre plots? First, the potential for a catastrophic wildfire can be greatly reduced by burning these areas under conditions of humidity, temperature, wind, and fuel moisture that allow the slash (from cutting before the Refuge acquired the land), downed trees, and leaf litter to be consumed while having a low risk of a spreading crown fire. Second, we predict that Golden-cheeked Warblers will be more productive in juniper-oak woodlands with high canopy cover and high tree species diversity. We are hoping to increase oak canopy cover by promoting recruitment of oaks and reduce dense stands of young juniper (not eliminate – “all things in moderation” as Benjamin Franklin proffered) that invade areas where fire is excluded.
Each of the sites being burned is paired with a control site. Researchers collected data on the vegetation and warblers on all the sites in 2012. Data will be collected on all the sites again in a framework termed a Before-After-Control-Impact study design. The difference on each plot is calculated for data from before and after the treatment. Then, the difference of these differences is calculated for each pair of sites. The first difference (Before minus After) accounts for changes that occur over time, with the natural variation accounted for on the control plots. The second difference (Control minus Impact) then accounts for the change that was actually due to the treatment, in this case the fire.
Managing natural resources requires setting objectives, implementing actions to achieve those objectives, monitoring the resources to learn and assess if the objectives are being met, and then modifying or changing actions as warranted. Often, we need to conduct experiments to assess new techniques. Results from this experiment will inform land managers on the role of fire in management of juniper-oak woodlands for Golden-cheeked Warblers. That smell of smoke will soon be replaced by the sound of Golden-cheeked Warblers. Last year the first male was observed at Warbler Vista on March 3. So, get out there on the trails and enjoy the sounds of spring.