| Vegetation dynamics, the core-satellite species hypothesis, and population dynamics of core, intermediate, and satellite species were studied in managed and unmanaged shale and sandstone glades, southern Illinois. Data resulted from vegetation sampling of forty 0.005 ha permanent plots surveyed during autumn 1995–1998, for species cover. The unmanaged shale glade sites (Berryville and McClure School) are succeeding towards a closed-canopy xeric forest and Touch of Nature sandstone glade has succeeded to a closed-canopy xeric forest as shown by GIS techniques and Detrended Correspondence Analyses. The managed site (Brown shale glade) has been succeeding towards a restored site characterized by a xeric prairie. This suggests that prescribed burning and woody tree removal have returned this site to more of a pre-settlement condition. Without restoration the other sites will eventually be lost as the forest canopy closes. Species distributions from forest openings were examined and were found to follow the predicted patterns of the core-satellite species hypothesis at all scales of analyses (site, site-type, and region). Population growth rates of core, intermediate, and satellite grass species responded positively to the restoration at Brown shale glade. In particular, biennial prescribed burning had profound effects on population dynamics of selected core, intermediate, and satellite species. This includes a significant difference in the growth rates of core, intermediate, and satellite species. It is speculated that there is a minimum population size threshold for successful recruitment of Schizachyrium scoparium seedlings into the general population. Core species outcompeted intermediate and satellite species and intermediate species outcompeted the satellite species across all density levels. This study provides an alternate methodology, statistical design, and analysis to study multi-species competition. Specifically, this includes the Simplex-lattice axial response surface design. This experimental design and associated Scheffé regression models allow the use of mixtures of species that naturally occur in nature. Overall, the findings presented here (community dynamics, species composition, species distributions, and the interaction of core, intermediate, and satellite species) suggest that fire dependent communities have multiple modes of abiotic and biotic interactions. The vegetation dynamics of managed sites show that there is greater directional change than the unmanaged sites. |
