The goal of the present study was to determine the quality of a late successional prairie located in Macoupin County, Illinois, and to examine plant community structure. The site is believed to have been cropped at some point in the past, but has now been lying fallow for about forty years experiencing occasional fires and mowing. It was hypothesized that the site would have low floristic integrity since no restoration or management practices have been routinely implemented. Vegetation cover data were collected in early and late summer of 2011 and 2012 from 102 plots located randomly throughout the site. Species richness (S), antilog of Shannon diversity (N 1), average coefficient of conservatism (mean C) and Floristic Quality Index (FQI) were calculated for each sampling session. These were also calculated for a comprehensive species list from the study site and four sites of known quality for comparison (N1 was not included in these calculations due to a lack of abundance data). Bray-Curtis dissimilarities were also calculated based on the species composition of these sites. Auchenorrhyncha (Insects: Hemiptera) were collected on four 40 m transects within the site. Auchenorrhyncha Quality Index (AQI), S, N1 and mean C were calculated based on count data from these transects and others located in eight comparison sites. A 3D ordination was constructed using non-metric multidimensional scaling (NMDS) and vectors representing the diversity indices as well as site size were fitted to the ordination. Analysis of the abundance data showed that from 2011 to 2012 there was a decline in all four diversity index scores. This was likely due to an extended drought period that occurred in 2012 and further studies are necessary to determine if the plant community can recover and stabilize after the disturbance. Comparisons between the study site and other high quality restorations and remnants revealed that the site does indeed have high floristic integrity, contrary to the hypothesis, though it was not very similar to any of the other sites in species composition. Results from the Auchenorrhyncha survey were consistent with those of the vegetation survey. When compared with those of other high quality sites, diversity index scores from the study site were all very similar and in some cases higher. This, again, was contrary to the hypothesis. In the ordination, transects clearly grouped based on the site they occurred in, and Axis 3 was negatively correlated with S though only slightly. A 3D ordination using NMDS was also constructed for vegetation abundance data collected from the 102 random plots. Vectors for a number of variables (average coefficient of conservatism (mean C), average wetness coefficient (mean WC), organic matter content (%OM), and year) were fitted to the ordination to determine which ones were driving the community structure. The vector for mean C was positively correlated with Axis 1, while the vector for year followed a similar trajectory in the opposite direction. This shows the same thing as the diversity variables calculated for species within the plots, that from 2011 to 2012 there was a drop in the mean C for the site, again likely due to drought. On Axis 1, there is a slight separation of plots occurring in the northern half of the site from those occurring in the southern half. This may be due to increased disturbance experienced by the southern sections because of their proximity to buildings. This may also be an artifact of the apparent bias towards dry-habitat species that exists in the designation of C values, as the southern sections remain relatively wet well into late summer months. The vector for mean WC is negatively correlated with Axis 2, revealing that Axis 2 likely corresponds to environmental variables associated with water availability. The vector for %OM is negatively correlated with Axis 3, which corresponds to factors that affect the development of organic matter in the soil. These factors include topography, which can directly affect soil moisture. Higher moisture levels lead to higher organic matter content. Thus, seemingly, the major gradients driving plant community structure in the study site are all related to water availability. Results of this research will be useful in determining what management strategies should be used for the persistence of this prairie habitat. (Abstract shortened by UMI.)
|Commitee:||Minchin, Peter R., Schulz, Kurt|
|School:||Southern Illinois University at Edwardsville|
|School Location:||United States -- Illinois|
|Source:||MAI 52/04M(E), Masters Abstracts International|
|Subjects:||Plant biology, Ecology|
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