Vegetation change in response to a tornado and prescribed fire in the Hickory Creek unit of the Big Thicket National Preserve, Texas

A mixed pine-oak forest in the Hickory Creek unit of the Big Thicket National Preserve was hit by a tornado in December of 1983. Subsequently the forest was subjected to three prescribed fires in an effort to restore this area to its former savanna state.\nThe tornado has allowed for both pines and oaks to regenerate. Both groups have regained much of the basal area lost in the tornado. However, the biggest compositional change has occurred at the understory level. There has been a huge increase in the upland shrub Ilex vomitoria (yaupon).\nVegetation composition and density seem to be involved in a positive feed-back loop with fire. Plots dense with shrubs experienced low flame heights, which has allowed for increased shrub growth. This process seems to be leading the tornado plots down a spiral towards unflammability. The current fire regime of periodic winter fires has only been able to slow this process in the most open plots. A more intense use of fire, such as repeated summer burns appears to be necessary to reclaim this area as a fire-dependent savanna.