Effects of wildfire on stand structure and composition in Guadalupe Mountains National Park, Texas

Authors: John Sakulich*, Regis University, Alan H. Taylor, Pennsylvania State University
Topics: Biogeography, Paleoenvironmental Change, Environmental Science
Keywords: Mixed conifer forest, vegetation dynamics, wildland fire
Session Type: Paper
Day: 4/4/2019
Start / End Time: 9:55 AM / 11:35 AM
Room: Regency Ballroom, Omni, West
Presentation File: No File Uploaded

Wildfire is an important natural disturbance agent in mixed conifer forests of the southwestern United States, but patterns of fire occurrence were highly altered beginning in the late 19th century when fire was excluded through livestock grazing and fire suppression. The absence of fire from these fire-adapted forests has increased tree density and accumulation of fuels. This study investigates the ecological effects of a recent wildfire in mixed conifer forests of Guadalupe Mountains National Park—a region subject to fire exclusion beginning in the early 20th century. In 2016, the Coyote Fire burned through the study area of a previous research project that quantified forest composition, structure, and historic fire regimes. In this follow-up investigation we re-sampled plots from the prior study and analyzed fire effects, tree regeneration, and fire-induced forest dynamics. We compared post-fire (2017) stand composition and structure, pre-fire (2003) conditions, and a dendroecological reconstruction of conditions present at the time of the last major fire (1922). While fire exclusion altered the composition of stands by increasing the relative abundance of Douglas fir, the 2016 fire did not cause substantial shifts in species composition. However, the recent fire did reduce live tree density and basal area by approximately 50%. The most dramatic change in stand structure occurred in plots dominated by Douglas fir, where live basal area was reduced below pre-fire exclusion levels. This research presents an opportunity to examine fire effects from a natural wildfire where the pre-fire forest conditions are known.

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