Loamy Upland

Description

The Reference State (1) comprises the communities within the range of natural variability under historic conditions and disturbance regimes. Patterns created by wildlife use and fire supported a mosaic of communities across the landscape. Warm-season tall grasses are dominant and warm-season mid grasses are subdominant. Cool-season grasses, forbs, and shrubs are minor functional/structural groups. Eastern gamagrass is naturally absent to rare in the northern half of the MLRA but becomes increasingly common southward. Conversely, cool-season grasses, such as porcupinegrass and Canada wildrye, are more prominent northward. High perennial grass cover allows for increased soil moisture retention, vegetative production, and overall soil quality.

Fire and bison herbivory were the dominant disturbance regimes that historically maintained the tall grass dominance with a diverse forb component. Furthermore, bison grazing was closely linked to fire patterns as the animals preferred grazing burned areas offering highly palatable and nutritious regrowth. Thus, historic plant communities were subject to occasional burning and grazing, with substantial rest/recovery periods as the fuel load rebuilt to eventually start this process again. Fires also served to suppress woody species and to maintain an open herbaceous stand. The degree to which current conditions represent this state largely depends upon how closely contemporary management has mimicked these past disturbance effects.

The Reference State (1) includes the Reference Community (1.1) which is dominated by warm-season tall grasses and the At-Risk Community (1.2) which is dominated by warm-season mid grasses.

Submodel

Description

The Native/Invaded Grass State (2) exhibits a co-dominance of both native and introduced species. Native, warm-season, tall grasses such as big bluestem and Indiangrass, may be present as a minor or trace functional group. The plant community consists of the more grazing tolerant native species and a significant component of introduced, cool-season grasses such as smooth brome, tall fescue, and Kentucky bluegrass. Forb diversity is limited to less palatable species such as ironweed and western ragweed. Plant diversity is low.

Impaired energy capture and altered hydrologic function are reflected in reduced vegetative productivity, shallower rooting depth and degraded soil quality. Continuous and heavy grazing pressure will maintain this plant community in a sod bound condition. Grazing management practices that allow for adequate periods of recovery between grazing events and grazing timed early and late during the growing season will reduce the vigor of the non-native, cool-season grasses and may allow the warm-season, tall and mid grasses to increase in abundance and productivity. Return to the Reference State (1) is unlikely due to the loss of plant diversity, overall soil disturbance, and alterations to hydrologic function.

The Native/Invaded Grass State (2) includes the Native/Non-Native Grass Community (2.1) and the Introduced Cool-Season Grass Community (2.2).

Submodel

Description

The threshold to the Sod-busted State (3) is crossed as a result of mechanical disturbance to facilitate production agriculture. Extensive areas of this ecological site were plowed and converted to crop production by early European settlers and their subsequent generations. In addition to permanently altering the existing vegetative community, repeated tillage negatively impacted soil properties. Reductions in organic matter, mineral levels, soil structure, oxygen levels, and water holding capacity along with increased runoff and erosion as well as shifts in the populations of soil dwelling organisms were common on these sites. The extent of these changes depended upon the duration of cropping as well as crops grown and other management practices.

If farming operations are suspended, the site can be abandoned or seeded to permanent vegetation. Seedings are either a tame pasture forage mixture, the Seeded Pasture Community (3.2), or a mixture of native grasses and forbs, the Reseeded Native Grass Community (3.1). Abandonment results in the Natural Reclamation Community (3.3). Permanent alterations of the soil, plant community, and the hydrologic cycle make restoration to the Reference State (1) extremely difficult, if not impossible.

Submodel

Description

The Invaded Woody State (4) is the result of woody encroachment. Once the tree canopy cover reaches 15 percent with an average tree height exceeding five feet, the threshold is crossed. Woody species are encroaching due to lack of prescribed fire and other brush management practices. Bur oak, eastern red cedar, Osage orange, roughleaf dogwood, honey locust, and coralberry are some of the first woody species to increase. Although these woody species are native to North America, they were not historically a significant part of the Reference State (1). If allowed to continue with little or no disturbance, eastern red cedar, oaks, and elm trees eventually dominate the site. As the overstory closes, various processes act to increase woody dominance. Foliage from woody species shades the understory and intercepts rainfall increasing evaporative loss. Litter acts similarly and further reduces effective precipitation while also creating a less uniform resource distribution with nutrients concentrated under individual trees. Typical ecological impacts are a loss of native grasses, degraded forage productivity, and reduced soil quality. This state consists of the Invaded Woody Community (4.1).

Prescribed burning, wildfire, timber harvest and brush management will move this state toward a grass dominated state. If the Invaded Woody State (4) transitioned from the Native/Invaded Grass State (2) or the Sod-busted State (3) the land cannot be restored to the Reference State (1) as the native plant community, soils, and hydrologic function had been too severely impacted prior to the woody encroachment to allow restoration to the Reference State.

Submodel