Huisinga, K. D., D. C. Laughlin, P. Z. Fulé, J. D. Springer, and C. M. McGlone (Ecological Restoration Institute and School of Forestry, Northern Arizona University, Box 15017, Flagstaff, AZ 86011). Effects of an intense prescribed fire on understory vegetation in a mixed conifer forest. J. Torrey Bot. Soc. 132: 590–601. 2005.—Intense prescribed fire has been suggested as a possible method for forest restoration in mixed conifer forests. In 1993, a prescribed fire in a dense, never-harvested forest on the North Rim of Grand Canyon National Park escaped prescription and burned with greater intensity and severity than expected. We sampled this burned area and an adjacent unburned area to assess fire effects on understory species composition, diversity, and plant cover. The unburned area was sampled in 1998 and the burned area in 1999; 25% of the plots were resampled in 2001 to ensure that differences between sites were consistent and persistent, and not due to inter-annual climatic differences. Species composition differed significantly between unburned and burned sites; eight species were identified as indicators of the unburned site and thirteen as indicators of the burned site. Plant cover was nearly twice as great in the burned site than in the unburned site in the first years of measurement and was 4.6 times greater in the burned site in 2001. Average and total species richness was greater in the burned site, explained mostly by higher numbers of native annual and biennial forbs. Overstory canopy cover and duff depth were significantly lower in the burned site, and there were significant inverse relationships between these variables and plant species richness and plant cover. Greater than 95% of the species in the post-fire community were native and exotic plant cover never exceeded 1%, in contrast with other northern Arizona forests that were dominated by exotic species following high-severity fires. This difference is attributed to the minimal anthropogenic disturbance history (no logging, minimal grazing) of forests in the national park, and suggests that park managers may have more options than non-park managers to use intense fire as a tool for forest conservation and restoration.
The Journal of the Torrey Botanical Society
Vol. 132 • No. 4
Vol. 132 • No. 4