SPATIAL AND TEMPORAL DYNAMICS BETWEEN OVERSTORY STRUCTURE AND GROUND FLORA 
DIVERSITY OF TWO LIMESTONE GLADES IN PIKE COUNTY, ILLINOIS.

Michael J. C. Murphy and Sean E. Jenkins.  
Department. of Biological Sciences, Western Illinois University, Waggoner Hall, 
1 University Circle, Macomb, IL 61455.

Tallgrass prairie and associated communities once dominated Illinois and much of 
the Midwest.  Today, these communities are considered critically endangered, 
occupying less than two percent of their original area.  Highly fragmented 
remnants are currently disappearing, converting to closed canopy conditions 
after decades of fire suppression.  Consequently, a greater understanding of 
successional processes and their effects on grassland communities is necessary 
in order to enhance preservation efforts.  During the summer of 2001, study 
areas were established on two, limestone glade grassland communities on the 
bluffs of the Illinois River, in Pike County, Illinois – representing minimal, 
and high disturbance.  To assess patterns and effects of succession in these 
communities, tree and sapling age structure, distribution and composition were 
determined, spatial relationships analyzed, and ground flora 
diversity/distribution examined in relation to these overstory parameters.  The 
glades were found to have very different stem age distributions with markedly 
different ground flora compositions.  Stem compositions and densities within age 
classes between glades, also differed significantly.  Age histograms revealed 
recent periods of strong stem recruitment, with the highest stem densities 
occurring in younger age classes.  Preliminary analyses indicate strong spatial 
aggregation of stems occurring within multi-species age classes and within age 
classes comprised of specific species.  Preliminary analyses also indicate 
negative correlations between ground flora diversity/distribution and overstory 
stem density and species composition.  Analyses examining spatial 
attraction/repulsion between age classes, species, and age classes within 
species are currently underway.
      
Key words: limestone glades, spatial temporal dynamics, grassland communities, 
succession, habitat loss