Physiognomy and Structure: This is a mesic, tallgrass prairie alliance, dominated by a moderately dense to very dense layer of C4 grasses up to 2 m tall. Forbs are typically abundant in this alliance. Woody species are uncommon in most stands but can become abundant in the prolonged absence of fire.

Floristics: This alliance is a very widespread mesic tallgrass prairie, which occurs in central North America. Andropogon gerardii is dominant across this alliance''s range. Other abundant species include Schizachyrium scoparium, Sorghastrum nutans, Sporobolus heterolepis, and Hesperostipa spartea (= Stipa spartea) (northward). Pascopyrum smithii may occur in the western portions of the range. Forbs are abundant in stands of this alliance, especially in the more humid east. Among these are Aletris farinosa (in the east), Coreopsis palmata, Echinacea pallida, Helianthus grosseserratus, Liatris spicata, Liatris pycnostachya, Oligoneuron rigidum, Phlox pilosa, Ratibida pinnata, Silphium laciniatum (central), and Solidago spp. Diamond and Smeins (1988) found Galium boreale and Oxalis sp. to be more common in northern tallgrass prairies than in southern. Trees and tall shrubs are infrequent in high quality stands, especially in the Great Plains. Among those that may be found are scattered Symphoricarpos occidentalis (in the northern Great Plains), Rhus spp., and Quercus macrocarpa (in the central and eastern portions of this alliance''s range).

Dynamics:  This alliance is found in a climate that can support trees and shrubs but woody vegetation is inhibited by frequent fires, periodic drought, and, historically, by grazing from large ungulates (Anderson 1990b). Historically, fire-return intervals were short, estimated at between 2 and 5 years (Stambaugh et al. 2006, Landfire 2007a). The frequent but unpredictable fires created a patchwork of habitats across the landscape, with recently burned sites having less litter and forb cover and sites with infrequent fires possibly having more woody species and dense stands of grasses (Kucera and Koelling 1964). Lack of fire, grazing, or mowing results in a decrease in productivity due to the soil surface staying cooler and shaded longer in the spring (Rice and Parenti 1978, Hulbert 1988). Lack of fire allows tree cover to increase rapidly, especially on lower, more mesic slopes (Heineman and Bragg 1982). This alliance is well-adapted to 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 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.