Fire suppression alters understory community composition of oak-hickory forests in Great Smoky Mountains National Park, USA

Prior to the establishment of Great Smoky Mountains National Park in 1934, oak-hickory forests within the Park burned approximately every 10-15 years. However, since Park establishment, fire activity within GSMNP has been heavily suppressed. We examined understory herbaceous and woody species composition to determine the effects of fire suppression on understory vegetation in oak-hickory forests. We hypothesized that fire suppression has altered understory vegetation communities by decreasing species diversity and abundance in oak-hickory forests. We compared herbaceous and woody species composition and abundance among four sampling categories: unburned stands, and stands that had burned once, twice, and three times over a 20-year period (late 1960s to late 1980s). Preliminary results indicate that species richness was greater in burned areas compared to unburned areas for both herbaceous and woody species (P < 0.05), however, species evenness did not differ among the four sampling categories. Woody species seedling density was greatest in single burn areas compared to unburned, double, and triple burn areas (P < 0.05). Our study demonstrates the impacts of fire suppression in oak-hickory forests in the southern Appalachians. In particular, we showed that species richness and woody seedling density are affected by burn frequency. The results of our study suggest that prescribed burning may be used to increase understory species diversity and woody seedling abundance.