Fire and hardwood regeneration in central Texas

Background/Question/Methods The paucity of Quercus spp. and other hardwood recruitment in central Texas has been attributed to high deer densities.  A paucity of hardwood regeneration has also been reported from other regions, where it is often attributed to fire suppression.  The effect of fire on hardwood regeneration in central Texas had not previously been investigated.  Central Texas woodlands are co-dominated by Quercus buckleyi and Juniperus ashei.  J. ashei does not re-sprout after it is burned and is unpalatable to deer; all of the Quercus species can re-sprout and are relatively palatable.  Under current conditions of fire suppression, high deer densities, and no Quercus buckleyi recruitment, woodland community composition is likely to shift towards a monoculture of J. ashei.  We measured the effects of fire on the number, size, and growth of J. ashei and hardwoods, especially Quercus spp. (hereafter Quercus), to determine whether fire suppression is responsible for the lack of hardwood regeneration.  Data were collected in burned and unburned plots at three sites in Balcones Canyonlands National Wildlife Refuge.  Following FIREMON (Fire Effects Monitoring and Inventory Protocol), a standard in fire effects research, we recorded the number and size of all vascular plants in two plots in each treatment-site combination.

Results/Conclusions Burning increased the size of Quercus and other hardwood stems while decreasing the number of J. ashei stems.  Fire killed some J. ashei individuals: burned plots had fewer J. ashei saplings and mature trees.  Burned plots also tended to have fewer J. ashei seedlings.  Quercus individuals between 0.5m and 3m tall were more abundant in burned than in unburned plots; the same pattern appears if plant size is measured as basal diameter.  The average height of these individuals was also greater in burned plots.  The positive effect of fire on Quercus growth was likely the result of increased light following fire.  Increased growth rates would increase the probability that an individual stem would reach a height above deer browsing.  However, we found no evidence of increased Quercus recruitment following fire.  Possibly weather conditions and/or deer densities were not suitable for Quercus recruitment; fire alone was not a panacea.