The joint effects of deer herbivory and fire on hardwood regeneration on the eastern Edwards Plateau

Background/Question/Methods

Failure of Quercus buckleyi regeneration has been documented in eastern Edwards Plateau woodlands. Similar regeneration failure has been observed in other hardwood species in these woodlands, although little research has been done to quantify this. In other regions, fire suppression has been suggested as a factor in hardwood regeneration failure. White-tailed deer (Odocoileus virginianus) herbivory has also been shown to negatively affect regeneration in Quercus spp. and is thought to be a factor in the regeneration failure of other hardwood species. This study examines the separate and joint effects of fire and herbivory on hardwood regeneration in eastern Edwards Plateau woodlands. Measurements were made on hardwood species in 2 different treatments (burned or control) at 6 different sites. To quantify browsing, the proportion of twigs that had been browsed in the current year was measured on individual plants.  Their size (basal diameter) was also measured.  Sites were characterized by cover, slope, soil type, and other environmental variables.

Results/Conclusions

The most common species was Quercus buckleyi, which was found in 81.7% of the plots. The next most abundant species was Diospyros texana, which was found on 41.7% of plots. Pooling species and treatments and averaging sites, 11.1% of twigs were  browsed  (site averages: 2.7% to 21.1%).  Pooling species, treatment (burned or control) did not have a significant effect on browsing (p=.0714), although on average browsing was less frequent in burned areas.  There  was no significant interaction between treatment and site. Sites differed significantly in the frequency of browsing  (p<.001), likely due to differences in deer density and plant species composition.

Surface fires are being considered as a management tool  to promote hardwood regeneration. These results indicate that deer herbivory will continue after fire, although perhaps at a lower intensity, and must be addressed; fire is unlikely to be sufficient to ensure hardwood regeneration without deer management.