Forest Ecosystem: Roughly 38% of Illinois was forested in the mid 19th century; today, only 14% of the state remains forested. CTAP professionals recorded an average of 61 plant species (range 19-108) at 73 forest sites. These forest sites ran the gamut of condition from poor to excellent. Interestingly, CTAP forest locations supported no threatened or endangered species. Sensitive species, those found in relatively undisturbed habitats, averaged 1.1 species and occurred in only 21 of the 73 forest sites. Non-natives averaged a low 3.0 species, occurring at 58 of the 73 sites.
Most dominant species in the ground layer were native but often included Virginia creeper, wood nettle, and black snakeroot, all tolerant of disturbances such as frequent logging and grazing. Sugar maple saplings dominanted the shrub layer, while white oak, American elm, sugar maple, and black oak dominated the canopy.
Regionally, non-native species dominated the community. The northern third of
Illinois supported either garlic mustard, buckthorn, or shrub honeysuckle as
the dominant species in either the ground or shrub layer (Table 3).
Alternatively, multiflora rose and Japanese honeysuckle dominated in 7 of 35 sites in central Illinois. Southern Illinois supported non-natives in the forest, but they only rarely reached dominant status.
Seven area-sensitive, forest-dependent bird species occurred on average at CTAP professional sites. These species generally decline in abundance as forest habitat is fragmented (becomes smaller and more isolated). Ten of the 24 species listed in Table 4 are highly sensitive to habitat fragmentation. An average of 0.67 of these species occurred at CTAP sites. Although historical data are lacking on the diversity and abundance of these 10 species, an average of less than 1 species per site clearly reflects the degraded condition of forest patches in Illinois.
Fragmentation of forest habitat leads to greater edge availability. These edges often harbor the Brown-headed Cowbird, a nest parasite of many birds. Cowbirds had greater detection rates than any other bird except the White-breasted Nuthatch, which highlights the Cowbird's potential for impact on the reproductive success of forest birds in Illinois.
ForestWatch volunteers reported that disturbance-sensitive plant species (blue cohosh, white flowered trilliums, Dutchman's breeches, squirrel corn, doll's eyes, bellwort, hepaticas, Virginia spiderwort, and maidenhair fern) occurred at less than 20% of the 133 sites monitored. The most common of these were squirrel corn and Dutchman's breeches, present at 19% of the sites. The rarest disturbance-sensitive species, the hepaticas, occurred at only 6% of the sites.
Volunteers found that non-native ground-cover species outdistanced disturbance-sensitive natives by a 2.5X margin in total area. Garlic mustard, the most common non-native ground-cover species, occurred at 31% of the sites investigated. In the shrub layer, non-natives averaged more than twice as many stems per hectare than natives. Anthracnose, a fungal pathogen of flowering dogwood, occurred at 5 of 16 sites where dogwoods were present. Volunteers reported no evidence of the gypsy moth, a tree leaf defoliator.
Volunteers reported evidence of a shift in community structure of forests whereby maple saplings tended to establish themselves better than did the oaks and hickories of the canopy. Eleven of 40 upland forest sites demonstrated this phenomenon. Volume 3 of the CTAP I report stated that between 1962 and 1985, maples increased by 41-fold, while oaks declined by 14%.
Grassland Ecosystem: In the 19th century, native prairies once covered approximately 61% of Illinois, generally dominating the landscape in central and northeastern Illinois. Roughly 2,300 acres of high-quality prairie remain, about 0.01% of the pre-European settlement acreage. Most of the grasslands currently listed in the land-cover database (6,932,409 acres, 19.2% of the state) are occasionally plowed, heavily grazed, or frequently mowed and do not resemble native prairies.
Professionals recorded an average of 20 plant species per site (range 6-33 species) at 71 sites. By comparison, high-quality prairie remnants may contain 100 to 140 species in only a few acres. Dominant native species included common goldenrod, red top, big bluestem, trumpet creeper, switch grass, and bead grass. CTAP sites supported few sensitive grassland species and samples revealed no threatened or endangered species. On the contrary, non-native species contributed about 38% of the average total species richness. Even though non-native richness was not extraordinarily high, this assemblage provided the dominant species at 84.5% of all sites. Cool-season grasses contributed nearly all of these non-natives, where they dominated most heavily in northern and central Illinois (Table 5). Most professional sites included pastureland, old fields, hayfields, and transportation rights-of-way, often planted in non-native grasses. Trees and shrubs were not dominant in any of the CTAP grasslands, since acceptable sites were limited to less than 50% tree and shrub cover. Non-native trees and shrubs included Osage orange, white mulberry, Siberian elm, and multiflora rose.
Professionals censused birds at 75 grassland sites during 1997-1999. The 12 species listed in Table 6 are area-sensitive, grassland-dependent species and their presence serves as an indication of grassland condition. Professionals detected an average of only 2.0 area-sensitive species per site. While a few of the 12 species in Table 6 do not occur statewide, this value is very low when compared to historical data gathered by other INHS scientists.
CTAP professionals detected Eastern Meadowlarks, a species of medium sensitivity, more frequently than any other species. It appears that this species does well in the small, degraded patches of remaining grassland habitat. From these data, it might be inappropriate to maintain its status of medium sensitivity. Professionals also reported that the Brown-headed Cowbird had a high rate of detection. Cowbirds reproduce rapidly, having the capacity to introduce their eggs into the nests of many birds in a single growing season. They represent a significant threat to sensitive-species reproduction.
A potential bellwether species in grasslands is the Bobolink, whose numbers declined by over 90% in Illinois since 1966. Cropping, overgrazing, excessive mowing, and the small size of most parcels negatively impact the reproductive success of this and other bird species. CTAP established minimum criteria for acceptance of grasslands related to these factors, resulting in rejection of many sites. Hence, the peril that Bobolinks and other species face may well be greater than implied by our data.
Currently, EcoWatch is piloting its PrairieWatch program. Their protocols complement those of professionals. Within a short time, depending on availability of resources, volunteers will be monitoring this troubled Illinois ecosystem.
Wetland Monitoring: Natural wetlands in Illinois have declined from pre-European settlement estimates of 23% of the land area to 2.6%. Only 6,000 acres of high-quality wetland remain in Illinois, a little over half of all remaining wetlands. Wetland loss in the state has been the result of draining, filling, dredging, and urban development. Our remaining wetlands have degraded further due to fragmentation, siltation, altered hydrological conditions, and by the invasion of introduced species.
Professionals sampled 78 emergent wetlands between 1997 and 1999, and recorded 15 species (range 1-19) on average. Sensitive species richness was less than 0.2, with no threatened or endangered species. Sensitive species included snowy campion, rough bedstraw, bristly smartweed, northern bugleweed, and comb pondweed.
Non-natives averaged only two species per site; however, they often dominanted to the point of forming near monoculture when present. Table 7 demonstrates that of these non-natives, reed canary grass was the most dominant, especially so in northern and central Illinois. The common reed (Phragmites sp.), though considered native, has become invasive in disturbed wetlands of southern Illinois, usually forming an impenetrable monoculture when present. Common species detected in the shrub and tree layer included mostly native black willow, buttonbush, sandbar willow, green ash, silver maple, eastern cottonwood, peach-leaved willow, and American elm.
Professional ornithologists censused 80 sites from 1997 to 1999. Many of these offered little suitable habitat for wetland-dependent birds, and many times contained species more representative of grassland ecosystems. While many of the birds that use wetlands are able to live in other habitats (e.g., Red-winged Blackbird, Song Sparrow, Common Yellowthroat), the 31 species listed in Table 8 are truly wetland-dependent. Their presence serves as an indicator of wetland conditions. At least 18 of these species utilize wetlands in southern Illinois, while at least 27 species occur in the north.
Statewide, professionals detected only 19 wetland-dependent species known to occur in Illinois, reporting only 1.3 of these species per site. A disheartening finding was that more than 55% of the wetlands supported no wetland-dependent species. Twelve of 35 threatened or endangered bird species in Illinois depend upon wetlands to forage and rear young. Professionals detected only three of these species at only three (3.8%) of the sites. This rarity further reveals the degraded condition of the average Illinois wetland.
CTAP Streams: Most stream courses at the turn of the 20th century were sinuous, associated with rich marshes that ameliorated flooding, had a treed riparian zone, and supported a diverse community of plants and animals. Streams of today face myriad challenges including nonpoint-source pollution (diffuse sources running off the landscape), channelization, erosion, sedimentation, and hydrologic modification. These disturbances and the point-sources of past and present have had severe impacts on the condition of our waterways. Irretrievable losses include the local extirpation or complete extinction of 11 fishes, 17 mussels, and several sensitive aquatic insects species.
CTAP professionals have sampled up to 120 stream sites during 1997-2000. Their primary indicators support the contention that streams in Illinois run the gamut from high-quality systems, worthy of Outstanding Resources Waters designation, to exceedingly poor conditions. The stream habitat quality index measures the condition of 12 parameters. A composite score, ranging from 0 to 180 (with 180 being of highest quality), was calculated for each of 87 sites monitored from 1997 to 1999. It provided a measure of the potential for in-stream and streamside habitat to provide food and shelter for aquatic organisms. This was the least forgiving of all stream indicators used by professional aquatic biologists. Statewide it averaged 88.6 points (range 25-146), a poor to fair rating. Figure 3a depicts an average Illinois stream, while Figure 3b depicts some of the best quality available.
Ephemeroptera, Plecoptera, and Trichoptera (EPT) species richness, an assemblage of insects that runs the gamut of sensitivity to pollution (but also contains some of the most sensitive aquatic species), averaged 7.1 taxa statewide (range 0-17). The Hilsenhoff biotic index (HBI) is an index of organic pollution in streams. This index runs from 0 to 10; a stream with HBI of 10 is of poor condition. It averaged 5.2 units (range 3.1 to 7.0) statewide. A midrange average such as this indicated that most streams sampled (and by virtue of these being randomly chosen, most streams statewide) were dominated by moderately pollution-tolerant EPT species indicating current or past degradation to a moderate degree. Even those sites with high EPT species richness, at least in the northern 4/5ths of the state, also had HBI values between 5.0 and 6.0. The presence of non-native aquatic insects is not an issue in streams yet. The Asian tiger mosquito now resides in Illinois, but it is not normally a stream species.
CTAP fish biologists monitored 58 sites in 1998 and 1999. The number of native fish species averaged 13.6 (range 1-30). Non-native species and hybrids occasionally thrive under the disturbed conditions characteristic of the state's streams. Currently, 15 non-native species reside in the state, and average only 0.2% of total native species richness. It appeared that the number of non-native species in the usually small drainages sampled by CTAP aquatic biologists was of minor importance. CTAP also utilized fish gathered by IDNR Fisheries and IEPA personnel as part of their five-year rotation through major river basins. Most of these streams were larger than those currently sampled by CTAP and provide a means to evaluate the condition of larger streams. These streams apparently supported a greater percentage of non-native species, but usually less than 3%. The Pecatonica and Des Plaines river basins produced exceptional values, approximating 7 and 8% non-natives as a proportion of native species. The Des Plaines watershed is highly urbanized, while the Pecatonica watershed is dominated by row crop agriculture and a large dairy industry.
RiverWatch volunteers have aided professionals by sampling tremendous numbers of sites, many in multiple years (Table 9).
Volunteer data come to much the same conclusion as do the professional data. Total taxa richness averaged 8.9 out of 33 possible taxa, with only 3% of sites providing 15 or more taxa. Statewide, EPT richness averaged 2.6 taxa (range 0-9). This is much lower than reported by professionals because RiverWatch tracks only nine EPT categories. Professionals potentially could encounter any of hundreds of species. A distressing point was that 13% of the more than 1,300 individual samples provided no EPT (e.g., sensitive) taxa, indicating severe degradation.
The Illinois Streams Information System (ISIS) organizes streams into 10 large basins and smaller subunits. The ISIS basins facilitate comparison of geographic trends in CTAP stream data (Table 10).
The availability of several aquatic indicators and indices demonstrates that they do not always agree. No ISIS basins scored high on all indicators. The Spoon River, for example, scored high in all measures of macroinverte-brate diversity and pollution tolerance, meaning a diverse macroinvertebrate community of pollution-intolerant species typified the streams in the watershed. On the other hand, the watershed displayed only average habitat quality and below-average fish diversity. The Embarras/Vermilion South watershed supported both diverse macroinverte-brate and fish communities, but poor HBI and MBI values. This suggested that the species, however diverse, tolerated moderate levels of organic pollution. Several watersheds scored at or below the average for most indicators. These included the Rock, Fox/ Des Plaines, and La Moine basins. One watershed, the Kaskaskia, scored consistently low on virtually every indicator.
In a couple of instances, the volunteer and professional data seemed contradictory. For example, professionals and volunteers came to vastly different conclusions about the Little Wabash basin, but so few sites were sampled by each that no valid comparison could be made. In the Big Muddy /Saline /Cache, professionals reported below-average conditions, reflecting the intensively farmed nature of the randomly selected sites. Volunteers mostly monitored attractive streams in upland areas of the Shawnee National Forest, an area of the state in relatively pristine condition. CTAP expects these discrepancies to diminish with the addition of random RiverWatch locations. Recent joint quality control efforts involving RiverWatch volunteers and professional aquatic biologists demonstrated that a few areas of improvement in protocols and training are necessary. Importantly, significant and strong correlations (parallels) between some RiverWatch and professional indicators occurred. These indicators will be useful for making broad generalizations about stream condition, and possibly in predicting some of the professional indicators. In this way, one half of the program informs the other and helps CTAP meet the goal of describing the condition of Illinois ecosystems.
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