15. Fults Hill Prairie Nature Preserve in Monroe County, Illinois showing margin of limestone glade with spcialized species including the Missouri Orange coneflower (Rudbeckia missouriensis), a state-endangered species in Illinois.
OBJECTIVES What are the major vegetation types that have occurred in Illinois and how have they changed since the last ice age and more specifically since European-Americans settled the region? Ecological factors influencing trends, composition, and diversity in prairie, savanna, open woodland, and forest communities are examined. Historical and co...
... Only about 0.01% remains in relatively undegraded condition (White, 1978;IDNR Natural Heritage Database, 2009). Of these prairie remnants, 241 in number, 79% are smaller than 10 acres and 23% are less than one acre (Taft et al., 2009). Other prairie remnants exist but most are degraded. ...
We propose that patterns of plant functional group occurrences could be a reliable indicator of prairie vegetation quality. A method for assessing tallgrass prairie quality based on density and composition of plant functional groups was developed and tested by comparison with qualitative indices calculated from species data at 17 prairies in Illinois. Species sample data were recorded from quadrats while functional group data were recorded from segments of belt transects overlying the species sample transects. Prairies selected include remnants and restorations and represent a wide range of habitat quality including recognized natural areas, degraded remnants, and prairie plantings of varying age and success. For agglomerative clustering of prairie quality classes, a matrix of habitat indices and metrics was used based on species sample data from all sites. Three groups were identified in cluster analysis that were characteristic of high, medium, and low-quality prairies. Mean Functional Group Density (Mean FGD), an index developed based on the mean products of frequency and density among plant functional groups recorded from belt transects at each site, had the highest correlations to habitat quality indices among two other functional group indices tested. Mean FGD was highly correlated with the mean coefficient of conservatism and floristic quality index, indices calculated from species sample data that have been shown to be reliable indicators of habitat quality. In means comparison tests among prairie quality classes, Mean FGD differentiated high-quality from medium and low-quality prairies, but did not distinguish medium from low-quality sites (only two low-quality sites were identified), although rank order of Mean FGD was as predicted. There is a tradeoff in efficiency and precision between species-level and functional group sample data. Species-level data more precisely discriminate differences in low and medium-quality sites; however, functional group sampling is much more rapid requiring only 20-to-25% of the time required for collecting species-level data. Results from functional group sampling highlight differences in functional group composition among prairie quality classes. High-quality prairies are characterized by greater abundance of sedges and hemi-parasites while lower-quality prairies were affiliated more with non-native perennial forbs and annual/biennial species.
Historical reference conditions provide important context for creating ecological restoration and management plans. The U.S. 19th Century Public Land Survey (PLS) records provide extensive ecological information for constructing such reference conditions. We used PLS records to reconstruct pre-Euro-American tree species cover class and vegetation structure types for the Midwest Driftless Area, a 55,000 km2 region currently experiencing multiple conservation threats. We related cover classes to soil texture, topographic roughness, and distance from waterway. Our analyses revealed that the landscape of the Driftless Area was mostly composed of savanna, with two large patches of closed forest and smaller, scattered patches of closed forest, open woodland, and prairie. The Driftless Area was heavily dominated by a variety of oak communities, with bur ( Quercus macrocarpa ), white ( Q. alba ), and black ( Q. velutina ) oak by far the most dominant species across the region. A variety of non-oak communities occurred within the closed forest patches, along rivers, or in smaller areas near the periphery of the region. The prevalence of savanna and oak communities indicates that fire played a key role in mediating historical landscape patterns and ecosystem processes in the region. Variation in soil texture, topographic roughness, and distance from waterways additionally contributed to the diversity of cover classes present prior to Euro-American settlement. Restoration practitioners can use our reconstructions to inform regional and site-specific restoration planning. Because oaks tend to be foundational species within ecosystems and are currently in decline throughout the Driftless Area, restoration activities that encourage these species are urgently needed.
Auchenorrhyncha (i.e., leafhoppers, treehoppers, spittlebugs, and planthoppers) represent some most diverse groups of herbivorous insects in the tallgrass prairie, they have close associations with many native prairie grasses and forbs, and respond in predictable ways to changes in grassland degradation. These attributes make Auchenorrhyncha ideal candidates in the development of a habitat quality index to measure tallgrass prairie integrity. Chapter 1 provides a detailed introduction of ecological integrity, methods used in measuring tallgrass prairie integrity, and the usefulness of insects in assessing prairie integrity. Chapter 2 describes the development of the Auchenorrhyncha Quality Index (AQI), and examines how changes in robustness (vacuum and sweeping) and sensitivity (changes in time of year and prairie community) affected two versions of the AQI (with abundance [AQIw/N] and without abundance [AQIw/outN]). The AQI was computed by assigning each auchenorrhynchan species a Coefficient of Conservatism (CC) value, which ranged from 0 (habitat-generalist/tolerant to degradation) to 18 (prairie-dependent/intolerant to degradation). These CC values are averaged and combined with species richness producing the AQIw/outN or these values are summed and weighted with abundance and combined with species richness producing the AQIw/N. The robustness and sensitivity of both versions of the AQI were analyzed by collecting Auchenorrhyncha from 35 sites in 4 states (Illinois, Wisconsin, Iowa, and Missouri) over 3 years (2004, 2005, and 2008) using a combination of sweeping and/or vacuuming from transects and/or 5x5m plots from wet-mesic, loess, glacial-drift, gravel hill prairies, and sand prairies. ANOVAs showed that both versions of the AQI were insensitive to changes in time of year and prairie community at the landscape level when sampling from four transects using a vacuum but both versions of the AQI exhibited variation on individual sites when vacuum or sweep sampling throughout the growing season and on wet prairies. Chapter 3 examined the ability of the AQI and related measures of Auchenorryncha integrity, and vegetation-based measures of integrity and diversity in discriminating glacial-drift hill prairie quality on 14 sites in Illinois; and examined the relationships between Auchenorrhyncha integrity and diversity and vegetation integrity and diversity. Both Auchenorrhyncha and vegetation integrity discriminated quality in similar ways and prairie Auchenorrhyncha diversity was positively associated with native prairie grasses. Chapter 4 examined the effects of prescribed burning on the AQI and related measures of Auchenorrhyncha integrity and diversity on 22 loess hill prairies in Illinois. These results showed that recently burned and frequently burned sites exhibited lower Auchenorrhnyncha integrity and diversity values than unburned prairies.