The effects of fire on the vernal herbs of an eastern mesic forest

Background/Question/Methods

Historically, fire has had a huge impact on the ecology of eastern forests.  Studies have shown how it affects the tree species composition and age distribution.  But the effect of fire on vernal herbs in mesic forests has been ignored.  The purpose of this study was to determine if prescribed fire will influence the species richness, presence of rare and common species, and density of exotics in the vernal herbaceous layer in an eastern mesic forest.  To determine these effects, three sites in a mesic forest in central Kentucky were surveyed prior to- and following one of three treatments: spring burn, winter burn, or control.  Low-intensity spring burns were conducted in April 2010 while winter burns were conducted in February 2011.  We analyzed the influence of fires and season of fire on species richness, abundance of rare species, abundance of common species, and abundance of Glechoma hederacea (an invasive herb).

Results/Conclusions

Species richness increased significantly across all sites due to fire treatment, with a 3% increase in the mean number of herbaceous species per plot (p < 0.006).  However, there was no significant difference in species richness due to the season in which the prescribed fire was conducted.  There were no significant differences in the abundances of rare species, common species, or Glechoma hederacea due to fire treatment or due to fire season.  Changes in species richness due to fire indicate that prescribed fire may be a suitable means of increasing the diversity of vernal herbs in the eastern mesic forest.  This study also shows that further research should be conducted to better understand the effects of burn season on the diversity of forest herbs, as well as fire’s effect on the abundances of both rare and common species in the herbaceous layer.