Fire effects on community structure, composition, and diversity in a dry sandstone barrens

Fire effects on canopy, shrub/sapling, and ground-cover species composition, structure, and diversity patterns were examined following two burns in a dry sandstone barrens remnant in southern Illinois. Vegetation was monitored at a fire treatment site and a nearby fire-free control site for three years following the first fire and two years following the second fire. Fire effects were most pronounced in the ground-cover stratum and least in the tree stratum. At the fire treatment site, tree species richness was unchanged while tree density (stems greater than or equal to6 cm dbh) declined 10.6% from a baseline total of 945 stems/ha to 845 stems/ha. There was additional tree mortality the second growing season following each fire. Quercus stellata remained by far the most dominant species. Fire effects were limited to small-diameter trees (less than or equal to15 cm dbh) while total tree basal area increased at the treatment site from 17.8 m(2)/ha to 18.22 m(2). Stem density in the shrub/sapling stratum significantly declined immediately following each fire while recovery to preburn levels was underway in four years just prior to the second burn. After two burns, stem density was about 45% the baseline amount. In the ground-cover stratum there were significant increases in diversity, species richness, species density, and percent cover at the fire treatment site while at the control site these variables remained unchanged or slightly declined. Noteworthy differences occurred among C-3 and C-4 graminoid species as many C-3 species (e.g., Dichanthelium spp., Carex spp.) increased greatly in frequency and percent cover with fire while C-4 species (e.g., Schizachyrium scoparium, Sorghastrum nutans) had parallel decline in the treatment and control sites.