The Tallgrass Prairie Ecosystem Prairies once accounted for twenty-four percent of the total land cover worldwide (Howell & Kline 1987). In North America, grasslands extend from the western boundary of the eastern deciduous forest to the base of the Rocky Mountains from southern Alberta and Saskatchewan to central Texas. The grasslands shift in composition and height with tallgrass prairie, mixedgrass prairie and shortgrass prairie distributed from east to west, respectively. The tallgrass prairie receives more rainfall, and has greater species richness and more dominant species than the shortgrass or mixedgrass prairie (Cochrane & Iltis 2000). Although grasses comprise only 10% of the species, they constitute most of the biomass in tallgrass prairies. The dominant grasses vary across a moisture gradient ranging from xeric (dry), mesic (moist), and wet prairies. Common grasses include little blue stem (Schizachyrium scoparium), big bluestem (Andropogon gerardii) and indian grass (Sorghastrum nutans). Forbs, another important prairie component, align themselves along a similar moisture gradient. These herbaceous species add seasonal color and texture to prairie vegetation. Besides grasses, the most common plant families in tallgrass prairies include composites and legumes (Cochrane & Iltis 2000). Climate change during the Holocene played a role in determining the distribution of prairie in the Great Plains. High temperatures and periodic summer droughts favor grassland over forest. Fire and grazing also influence the distribution of prairie, especially along the margins of its range. The rolling topography of the Great Plains covered with flammable plant material encourages the spread of fire through the landscape. The lightning fires and frequent burns by the Native Americans slows the invasion of woody species, hinders competitive grasses, and reduces litter in the prairie. Grazing by ungulates alters the landscape by removing plant material, concentrating nutrients, trampling, and influencing decomposition (Cochrane & Iltis 2000). Currently, the tallgrass prairie ecosystem is one of the most threatened ecosystems in the Midwest United States (Wisconsin Department of Natural Resources 1995). The relatively flat topography and fertile prairie soils encouraged the conversion of prairie for agricultural purposes. Of the remnant prairies that remain, most are dry prairies found on steep slopes, or mesic prairies located along railroads and in cemeteries. Due to an invasion by woody species, overgrazing, and poor management practices, many of these remnant prairies are severely degraded and have lost many plant species (Leach & Givnish 1996). Regional context The tallgrass prairie ecosystem occupies a large portion of the Upper Midwest region of the United States, including Minnesota, Wisconsin, Michigan, Indiana, Illinois, and Iowa. This geographic region has ample fresh water and fertile land. With the exception of Iowa, each of these states border at least one of the Great Lakes: Michigan, Superior, Huron, or Erie. Most of the Upper Midwest was once covered by the Laurentide Ice Sheet with the exception of the Driftless Area in southwestern Wisconsin and the southernmost reaches of Indiana and Illinois (Cochrane & Iltis 2000). The glaciers shaped the land in many ways, leaving behind moraines, outwash plains, and kettle holes. The resulting topography consists of gently rolling hills and large flat expanses punctuated by lakes. The region epitomizes the humid continental climate type characterized by warm summers and long, cold winters. The Great Lakes buffer the surrounding areas providing cooler summers and milder winters. The amount of rainfall ranges from 63 to 100 cm of precipitation annually (Mattson 1996) Figure 1. Mean monthly temperature (above) and precipitation (below) for Madison, Wisconsin, USA, for the years 1971-2000 (Lindstrom & Young 2002) Prior to European settlement, many factors including climate created a gradation of boreal forest and mixed hardwood forests in the north and tallgrass prairie and savannas in the south. Most of the fertile land that was once prairie and savanna has been converted into farmland and pasture. Corn, soybeans, dairy products and cattle are the most common agricultural uses, bringing in at least 3 billion dollars annually in each state (Mattson 1996). Significant areas were retained as woodlots, but these have grown up to form dense stands of shade-tolerant trees characterized by a reduced number of the oak species that were abundant. The richness of the prairie soils attracted immigrants from Northern Europe. By 1880, over two-thirds of all immigrant farmers had settled in the Midwest (Hurt 2001). The immigrants who settled in the region were motivated to improve their standard of living and brought “strong beliefs and moral values that encouraged hard work” (Hurt 2001). After many years of cultural give-and-take, the distinctive Midwestern culture emerged, characterized by a strong work ethic and moderate conservatism. Local context The Curtis Prairie is located in Madison, Wisconsin. As both the capitol of Wisconsin and home of the state’s largest university, Madison has a population of 298,054 (U.S. Census 2002). Curtis Prairie (W89.4°, N43.1°) is a restored tallgrass prairie that is situated within the University of Wisconsin-Madison Arboretum. It represents one of thirty-one biotic communities included in the University’s 500-ha Arboretum. Aldo Leopold, a forward- thinking professor at the University, recognized early on that native communities were being lost and suggested in 1934 that the Arboretum (then a farm) could ultimately provide a “sample of what Dane county looked like when our ancestors arrived here” (Blewett & Cottam 1984; Sachse 1965). Based on U.S. Government Land Survey records from 1835, the presettlement condition of the Arboretum consisted of oak openings and marsh. The uplands contained bur and white oaks with about 36 to 48 trees per hectare. Prairie grasses, prairie forbs and shrubby black oaks made up the ground cover (Blewett & Cottam 1984; Curtis 1951). The 25-hectare area that would become Curtis Prairie was first settled for farming in 1836. After eleven owners, the Bartlett family purchased the land in 1860. By 1863 the western two-thirds of the land was regularly plowed and planted with corn, oats and pasture in rotation. The wetter eastern third was probably not plowed, with the northern section undisturbed and the southern half used for a mowing meadow. The Bartlett family abandoned cultivation in 1920. The land was fallow until 1926 or 1927 when a veterinarian named West leased the land to pasture 35 to 40 horses. This pasture incorporated the eastern third of the property including the previously undisturbed section and the mowing meadow (Blewett & Cottam 1984). By 1932 the Arboretum was becoming a reality. In that year a part of the Nelson farm was purchased, and in 1933, the University of Wisconsin regents purchased the Bartlett farm. When the fields were purchased, quackgrass (Agropyron repens) dominated the fields. Eventually, two bluegrass species (Poa pratensis and P. compressa) took over (Blewett & Cottam 1984). All three species are considered weedy and non-native components of tallgrass prairies. The creation of a prairie within the Arboretum proved challenging. Not only was this the first ecological restoration, but also there was little tallgrass prairie habitat left to characterize reference conditions due to conversion to agriculture. In The Vegetation of Wisconsin, John Curtis (1959) estimates the original area of over 800,000 hectares has been reduced to remnants, with none larger than 16 hectares. Restoration approaches The restoration goal was to replace pasture and ruderal vegetation with species of native plants for use in research and education. Over the decades that followed the dedication of the Arboretum in 1934, scientists from the University of Wisconsin conducted many experiments involving planting methods and controlled burning. These experiments were aimed at increasing the number of native plant species and decreasing the abundance of weedy and exotic plant species. From 1936 to 1940, Dr. Theodore Sperry directed the first effort to establish a prairie with supervision from Aldo Leopold and William Longenecker. About 200 recruits of the Civilian Conservation Corps (CCC) planted 42 plant species in large blocks within 237 plantings. Three methods of planting were tested: seeds, seedlings and sod transplants. This approach likely represents the first example of experimentation in a restoration site. Prairie remnants along the Wisconsin River provided a source of native seeds and sods, and the seedlings were cultivated in a nursery within the prairie. The establishment rates for the planting treatments were similar, but the sod transplants had slightly higher survival; however, the expense of the sod techniques far outweighed the benefits (Blewett & Cottam 1984). Between 1950 and 1957, a second major planting program added 156 species to selected areas of Curtis Prairie. New planting methods were utilized: seed casting after a burn, hand insertion of large seeds, transplanting sods, and disking followed by seed casting with the addition of cover crops. The last method provided the best results (Blewett & Cottam 1984; Wilson 1964). Curtis Prairie also supported experiments on soil preparation, plant competition, controlled fire treatments, and germination studies. John T. Curtis, Professor of Botany at the University