The Nebraska Sandhills is the largest contiguous grassland in North America, and 95 percent of its 19,300 square miles is privately owned and used for beef production. Cattle share their pastures with wildlife, and the regional biodiversity of wildlife is enhanced by unique habitat components within the sea of grass: alkaline and freshwater wetlands, aquifer-sourced streams, and linear woody vegetation in riparian zones or windbreaks. Yet it is the upland grasslands that provide extensive areas of forage for cattle and a refuge-like area of habitat for a suite of grassland wildlife species.
Forage Resources
Around 90 percent of the Sandhills is upland prairie characterized by rolling dunes composed of fine sands in the Valentine series. The dominant native perennial grasses in this semiarid environment are palatable to grazing cattle and productive, producing as much as fifteen hundred to twenty-two hundred pounds per acre annually. Warm-season grasses, such as sand bluestem, prairie sandreed, little bluestem, and switchgrass, account for 40 to 50 percent of total aboveground plant production. Cool-season grasses, such as needleandthread, porcupine grass, prairie junegrass, Scribner rosettegrass, and sedges, account for 30 to 40 percent of production, with forbs (wildflowers) and shrubs accounting for the remaining 20 to 30 percent. As much as 80 percent of the perennial grass biomass is below ground in fibrous roots and rhizomes, which provide the water and nutrients required for the persistence of perennial grasses in this relatively harsh environment. The fibrous roots also are the major source of soil organic matter and are responsible for stabilizing the sand dunes.
Uplands are used almost entirely for grazing cattle, mostly during the growing season, although haying is a common practice on some ranches, particularly in high rainfall years. The other 10 percent of the Sandhills is wet meadow dominated by exotic cool-season grasses and some native warm-season grasses and sedges and rushes. Most wet meadows were ditched in the first half of the 1900s to drain surface water from these meadows and allow ranchers to use haying equipment by July. Wet meadows are productive, with annual average plant production of four thousand to six thousand pounds per acre. Because of high soil moisture availability, plants grow rapidly following the summer hay harvest and provide excellent forage for fall grazing.
Livestock Production
Sandhills ranches are a primary source of calves and yearlings for feedlots in Nebraska and are critical to the state’s $12.1 billion beef cattle industry. As much as 95 percent of Sandhills rangeland is privately owned and used for cattle ranching, with cow-calf enterprises on more than 90 percent of the ranches and stocker-yearling operations on about 40 percent of them. Most cow-calf enterprises calve from March to May and wean in October and November. Sandhills vegetation is a good match for these cow-calf enterprises because of the abundant, diverse, and high-quality forage plants available during the summer grazing season (May–October); much the same can be said for forage availability for stockers-yearlings. The dominant warm- and cool-season grasses also are grazing tolerant, providing a long grazing season. Sandhills uplands are stocked near grazing capacity, and the native grasses remain dominant.
Ranchers generally depend on beef as their sole source of income from the ranch, making economic sustainability of ranches a challenge, especially considering the variability in beef cattle markets and weather from year to year. To diversify and increase economic sustainability of ranches, enterprises built on the value of ecosystem services found in the Sandhills are being developed, including fee hunting and ecotourism. A significant portion of Sandhills rangeland is owned by people who do not live on the property. These absentee owners commonly have land-use goals other than beef cattle production.
Grazing Practices
The principal grazing season on the upland range of Sandhills cattle ranches is from mid- or late May to October or November. Uplands are the only source of forage for cattle during this five- to six-month grazing season. Sources of forage during winter and early spring are variable and include hay (mostly from the wet meadows), crop residue (mostly from neighboring cropland areas), and winter range in the Sandhills. Ranchers typically select rotational grazing systems in uplands during the summer season. Choices of duration, timing, and stocking rate create management alternatives that range from simple rotational grazing, where cattle rotate through two to seven pastures once during the grazing season, to management-intensive grazing with eight or more pastures and cattle rotating through the pastures multiple times (usually twice) during the grazing season.
Cow numbers in Sandhills counties have remained between 750,000 and 800,000 since the mid-1950s. Average liveweights of cows were a thousand pounds in the 1950s and 1960s but then increased to fourteen hundred pounds by the twenty-first century, primarily because of a transition to heavier breeds of cattle. Therefore, even though the number of cows on Sandhills grazing lands has not changed since the 1950s, liveweights increased by as much as 40 percent during the same period. Forage intake of individual animals increases with increasing liveweight, resulting in increased forage demand or stocking rate. This suggests that forage demand on grazing lands has increased considerably, with stocking rates increasing by as much as 40 percent. Some of this increase in forage demand has been met by using forage resources outside of the Sandhills, especially grazing cornstalks and other crop residues during winter in cropland areas near the Sandhills. However, much of this increase in forage demand has been met by increasing the efficiency of using available forage in the uplands. Distribution of grazing in large pastures with long distances between livestock water sites is commonly uneven, resulting in large areas that are not grazed or only lightly grazed along with areas that are heavily grazed. This unevenness, or patchiness, of grazing within pastures over a ranch property can be corrected by a number of different strategies.
The spatial distribution of cattle grazing, and associated plant defoliation, is more even for management-intensive grazing than with simple rotational grazing and continuous grazing. Over the last several decades, the USDA’s Natural Resources Conservation Service and university extension programs have promoted rotational grazing and reducing pasture size, while increasing livestock water sites to reduce distance to water. Overall, these practices have increased the evenness of grazing over space and time, which has increased the percentage of available plant biomass that grazing livestock consume and increased carrying capacity.
Grassland Heterogeneity and Wildlife
The diversity of wildlife habitat types in grasslands is largely dependent on the patchy distribution of vegetation cover. Heterogeneity describes the patchiness of vegetation over time and space as measured by height, density, and composition of vegetation. Vegetation is naturally patchy at landscape scales because of changes in topography, soils, and past management. Upland plant communities in the Sandhills, however, are relatively homogeneous throughout because of the continuity of sandy soil, dominance of the gentle rolling dunes, and management strategies that favor even distribution of grazing. As cattle evenly graze pastures, the vegetation cover of the pastures become homogeneous, and patches of wildlife habitat become less distinct. Evaluating the tradeoffs of implementing different grazing strategies is part of the decision-making process of ranchers to achieve their management objectives.
The effect of increasing homogeneity of habitat on wildlife varies by species. Biologists have documented three hundred species of resident and migratory birds in the Sandhills, fifty-five species of mammals, and twenty-seven species of amphibians and reptiles. Some species, such as western meadowlark, white-tailed and mule deer, and bullsnake are habitat generalists and can be found on a variety of habitats, including homogeneous grasslands. Others are habitat specialists and require unique patches of habitat. These species include northern prairie lizard (bare areas of blowouts), six-lined race runner (dense vegetation), meadow vole (wet meadows), and horned lark (bare ground). These specialists are the species affected the most by changes in habitat heterogeneity over time.
Managing for Habitat Heterogeneity
Ranchers use rotational grazing systems, fencing, and water distribution to spread livestock grazing evenly across pastures and to minimize creation of bare ground, thus reducing the risk of overgrazing that can reduce beef production in subsequent years. Rotational grazing systems have been touted as beneficial to wildlife diversity in grasslands across North America. Yet field measurements in the Sandhills during the past two decades have shown that the level of heterogeneity in Sandhills grasslands created by rotational grazing may not provide the extremes in plant structure and composition—very dense, ungrazed vegetation and bare ground—needed to provide habitat for a diversity of grassland animals.