Midwestern Sandy Tallgrass Prairie

This system is found in the northern Midwest, particularly in Minnesota, Wisconsin, Michigan, and possibly ranging into Ontario. It is often found on glacial features such as kames, eskers, moraines, lakeplains (though excluding the Great Lakes lakeplain) and sandplains, and along eolian dunes. In contrast to the deeper, richer soils supporting other tallgrass systems in the region, the underlying soils in this system tend to be more shallow, sandy, rocky, and/or gravelly outwash soils. Organic content is significantly lower. Grassland species such as Schizachyrium scoparium, Andropogon gerardii, and Bouteloua spp., varying in cover from sparse to moderately dense, dominate this system. Hesperostipa spartea and Sporobolus heterolepis are also common components of this system. Woody species more tolerant of droughty conditions may be found in some examples. The most common trees are Pinus banksiana, Quercus ellipsoidalis, Quercus macrocarpa, and Populus tremuloides. Fire and drought are the major dynamics influencing this system. If fire and periodic drought are not present, woody species begin to invade this system, especially in the eastern parts of its distribution. Wind can also play a role, especially on examples found on sandplains and/or eolian dunes.

Grassland species such as Schizachyrium scoparium, Andropogon gerardii, and Bouteloua spp., varying in cover from sparse to moderately dense, dominate this system. Hesperostipa spartea and Sporobolus heterolepis are also common components of this system. Woody species more tolerant of droughty conditions may be found in some examples. The most common trees are Pinus banksiana, Quercus ellipsoidalis, Quercus macrocarpa, and Populus tremuloides.

This system is often found on glacial features such as kames, eskers, moraines, lakeplains (though excluding the Great Lakes lakeplain), and sandplains, and along eolian dunes and river deltas. In contrast to the deeper, richer soils supporting other tallgrass systems in the region, the underlying soils in this system tend to be more shallow, sandy, rocky, and/or gravelly soils. Soil texture is sand or sandy loam. Organic content and soil moisture retention are significantly lower than the more mesic grasslands.

Fire and drought are the major dynamics influencing this system. If fire and periodic drought are not present, woody species begin to invade this system, especially in the eastern parts of its distribution. Fire-return intervals were likely 1-8 years (Landfire 2007a). Drier examples of this system likely could not be maintained in the presence of long-term short fire-return intervals due to the lower fertility of the soils. The typical dominant perennial grasses would not have time to recover from repeated burning and shorter-lived opportunistic species could dominate (Loucks et al. 1985). These sites were maintained as grasslands by the dry soil conditions possibly supplemented by low-frequency fires, while other areas required fire to eliminate invasion by woody species. Wind can also play a role, especially on examples found on sandplains and/or eolian dunes or during droughts when vegetation cover is low. Blowouts can form, exposing bare sand (Burgess 1965). Productivity is lower on this system than on other tallgrass prairies, so vegetation responds more slowly to disturbance. This system can not persist with the same frequency of reductions in vegetation cover by fire, grazing, drought, or mowing as richer prairies can.

Tallgrass prairie has been largely eliminated from the landscape due to conversion to agricultural uses, elimination of the landscape-level processes that maintained the system, and introduction of exotic species. Estimates across the range of all tallgrass prairie systems are that 82-99.9% of tallgrass prairie has been eliminated (reported in Samson and Knopf 1994). This system occurs in a region that is generally very fertile and suitable for crops. The soils on which this system occurs are less fertile than the general region and so more of this system has escaped outright conversion to cropland than richer prairie systems. In addition to loss through direct conversion to crop fields, farmland development has fragmented the natural landscape and has eliminated the large-scale processes of fire and grazing by native ungulates that were necessary to maintain some examples of this system. Those examples have been invaded by woody species and non-native forbs and cool-season grasses. Many examples of this system can tolerate moderate grazing over time or heavy grazing for short periods, but when used as long-term pasture and with high stocking rates, the dominant native grasses are reduced or eliminated. Heavy haying or grazing, or if those are done consistently during the mid-summer months, negatively affects the dominant warm-season grasses by removing their biomass before they have flowered. Cool-season grasses and forbs which set seed earlier are favored by these activities. Native and non-native forbs, woody species, and C3 grasses increase in the absence of fire, especially when combined with grazing by livestock. Drier sites on hilltops or rocky soils persist longer but more mesic sites on lower slopes can be invaded by trees and shrubs after just several years without fire. Non-native grasses have been planted for forage on some sites, as well.

This system is found in the northern Midwest possibly ranging into Ontario.