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| Algific slopes are north-facing rocky slopes that retain subsurface ice through most of the year. In Illinois they occur only in the Driftless Area. The cold microclimate created on the surface of the slope supports relict northern and Pleistocene biota, including many endangered, threatened, and rare species. |
Map of Site
Land Cover Map of Site
SIZE: 191,814 acres 300 square miles
LOCATION: Northwestern Illinois on the Mississippi River; Jo Daviess, Carroll and Whiteside counties.
The Driftless Area RRA occupies a physiographically unique part of the state that escaped Pleistocene glaciation. The area is characterized by rolling hills and a dis sected pattern of wooded ridges and includes such promi nent features as canyons, ravines, bluffs, and palisades. Some of the flora and fauna are distinctive and unique in the state, including several plant species which are northern species or preglacial and interglacial relicts.
LANDCOVER: The Driftless Area RRA has the highest percentage of grassland of all the sites (37%). (The grassland category in this publication
includes pastures, hayfields, idle fields, rural-road and railroad rights-of-way,
and prairie remnants.) The site is one-fourth wooded22% upland woods and
nearly 6% bottomland woods. Much of the woodland is found on ridges. Twenty
percent of the area is cropland; this is one of the few nonurban RRAs where
cropland is not the predominant landcover type.
NATURAL AREAS: There are 19 Natural Areas in this RRA. This site contains more Natural Area acreage than any other RRA (30,556 acres, 16% of the site area). The Savanna Army Depot accounts for approximately 14,000 acres; otter habitat and Spring Lake, a large lake associated with the Mississippi River, are other large Natural Areas.
BIOLOGICALLY SIGNIFICANT STREAMS: This site contains 22.4 miles of streams identified as biologically significant.
HERITAGE SITES: There are 109 Heritage occurrences in the Driftless Area RRA: three significant community types, 30 plant species, 20 animal species, and three rookeries.
STATE AND FEDERAL LAND: Mississippi Palisades State Park is lo cated in this RRA as well as one state fish and wildlife area. This site has the second highest percentage of area in federal ownership (21% of the area; 40,612 acres). Federal lands are the Upper Mississippi Wildlife and Fish Refuge (26,579 acres) and the Savanna Army Depot (14,033 acres). See sidebar on page 16.
NATURE PRESERVES: There are four Nature Preserves in this RRA. Significant features include sand prairie, sand dune and blowout, cliff, hill prairie, and seep springs.
NATURAL DIVISIONS: Nearly three-fourths of the Driftless Area RRA is comprised of the Wisconsin Driftless Division. This RRA is the only site that includes this division; 37% of
The Savanna Army Depot is currently being decommissioned as an ordance storage facility. It covers approximately 20 square miles and includes bottomland, oak forest, wetlands, upland sand prairie, and habitat for 32 endangered or threatened plants and animals. Approximately 9,000 acres will be transferred to the U.S. Fish and Wildlife Service for addition to the Upper Mississippi River Wildlife and Fish Refuge.
SUMMARY OF SITE CHARACTERISTICS: SIZE, BIOLOGIC RESOURCES, AND PUBLIC LANDS| Total Acreage | 191,814 |
| Natural Areas | |
| 30,556 |
| 19 |
| Biologically Significant Stream Mileage | 22.4 |
| Natural Heritage Sites | 109 |
| State Land | |
| 1 |
| 0 |
| 0 |
| 1 |
| Acreage | 3,354 |
| Percentage of RRA | 1.7 |
| Federal Land | |
| Acreage | 40,612 |
| Percentage of RRA | 21.2 |
| LANDCOVER | Acres | % of RRA |
| Upland forest | 41,587.13 | 21.68 |
| Bottomland forest | 10,643.35 | 5.55 |
| Wetland- nonforested | 1,119.55 | 0.58 |
| Grassland | 71,811.77 | 37.44 |
| Cropland | 37,603.67 | 19.60 |
| Urban/Built-up | 2,710.36 | 1.41 |
| Water | 26,338.33 | 13.73 |
| Total | 191,814.16 | 99.99 |
| ILLINOIS NATURAL AREAS INVENTORY SITES | Acres |
| Ayers Sand Prairie | 29 |
| Blackhawk Otter Habitat | 3,625 |
| Dixon Creek North Geological Area | 2 |
| East Dubuque Geological Area | 5 |
| Hanover Bluff | 164 |
| Jo Daviess County Otter Habitat | 6,550 |
| Mississippi Palisades | 412 |
| Mississippi Palisades Geological Area | 2 |
| Palisades Stickseed Site | <1 |
| Pilot Knob Geological Area | 1 |
| Princess Mine Algific Slope | 154 |
| Redroot Site | 1 |
| Rice Algific Slope | 49 |
| Royal Princess Geological Area | 3 |
| Savanna Army Depot | 14,323 |
| Savanna South Railroad Prairie | 61 |
| Spring Lake | 4,913 |
| Thomson-Fulton Sand Prairie | 262 |
| Wise Lake Geological Area | 2 |
| BIOLOGICALLY SIGNIFICANT STREAMS | Miles |
| Apple River, Wolf Creek to Mill Creek | 12.0 |
| Menominee River | 5.1 |
| Mississippi River, rm 545-550, Carroll Co. | 5.3 |
| NATURAL HERITAGE CATEGORIES | ||
| Communities | Occurrences | Types/Species |
| 1 | 1 |
| 2 | 2 |
| Threatened and Endangered Animals | ||
| 27 | 11 |
| 3 | 2 |
| 15 | 2 |
| 3 | 2 |
| 1 | 1 |
| 2 | 2 |
| Threatened and Endangered Plants | ||
| 29 | 21 |
| 1 | 1 |
| 11 | 7 |
| 6 | 1 |
| Geological Feature | 5 | 1 |
| Other | ||
| 3 | 1 |
| STATE AND FEDERAL LAND | |
| State Parks | Acres |
| 2,350 |
| State Conservation Areas | 0 |
| State Forests | 0 |
| State Fish and Wildlife Areas | |
| 1,004 |
| Federal Land | |
| 14,033 |
| 26,579 |
| NATURE PRESERVES | Acres |
| Ayers Sand Prairie | 23 |
| Hanover Bluff | 390 |
| Sentinel | 51 |
| Thomson-Fulton Sand Prairie | 83 |
| NATURAL DIVISIONS | Acres in RRA | % of RRA | % of Division |
| Wisconsin Driftless | 135,938 | 72.6 | 37.0 |
| Major Water Bodies | 21,236 | 11.3 | 1.9 |
| Up. Mississippi R and Illinois R Bottomlands | 18,658 | 10.0 | 1.6 |
| Illinois R and Mississippi R Sand Areas | 11,501 | 6.1 | 3.0 |