Clayey Upland Prairies

Description

The reference plant community is a warm-season tallgrass prairie that has diverse native grasses and forbs. Community phases within the Reference State are dependent upon the influences of grazing and frequency of fire events. Fire is a trigger that promotes continued herbaceous vegetation dominance and removes dense thatch thereby allowing for seedling regeneration. Fire removes plant litter, helps cycle nutrients, and allows light to reach the seedbed. Areas of this ecological site burn approximately every 5 years or less. Frequent fire maintains the community in a grassland state, by keeping fire-sensitive woody species from proliferating and gaining dominance.

The secondary trigger for conversion is grazing. Intensive grazing reduces the extent of highly palatable species thereby allowing the growth of less desirable plants to increase. Grazing management guidelines vary by site depending on site specifics and management objectives.

Dominant reference species include leadplant (Amorpha canescens), big bluestem (Andropogon gerardii), and switchgrass (Panicum virgatum). Numerous other grasses and forbs may be present, and high-quality sites will exhibit a diversity of native species. Today, high-quality, unplowed areas of the Reference State are extremely uncommon. Most remaining natural areas that are managed for tallgrass prairie were once tilled and utilized for agricultural production. It is therefore likely that many of the historic native prairie species are extirpated even from these sites.

Resilience management

Prescribed fire and managed grazing are key resilience management practices. This is a stable plant community when grazing and fire are adequately managed.

Prescribed grazing incorporates periods of grazing rest during the growing season which benefits tallgrass maintenance. Excessive grazing can quickly impact the vegetative composition and negatively impact soil stability.

Prescribed fire is the controlled application of fire to modify vegetation structure and influence ecological processes.

Submodel

Description

Tillage is the primary mechanism affecting the transition to this state. In this state, dynamic soil properties such as bulk density, structure, organic carbon content, and saturated hydraulic conductivity are altered by agricultural practices. Hydrological modifications (tiling and ditching) are commonly installed to improve drainage, so natural hydrology is altered. Most areas in this state will remain in use for crop production in the foreseeable future – primarily in an intensive corn and soybean rotation.

Certain practices can mitigate the impacts of traditional agricultural practices on soil health. Conservation tillage minimizes soil disturbance and can improve soil structure and overall soil health. Corn or soybean plantings and a cover crop rotation can build soil structure, improve infiltration rates, reduce runoff and erosion, and protect water quality.

Some areas in this ecological site are not appropriate for intensive crop production due to slope. Where the gradient exceeds 20 percent row crop production is not feasible due to limitations on farm machinery.

A small percentage of Clayey Upland Prairies ecological sites have been seeded back to grass. Some previously tilled areas have been converted to warm-season grasslands as part of the NRCS Conservation Reserve Program (CRP). Common warm-season grasses seeded in this community include big bluestem (Andropogon gerardii), Indiangrass (Sorghastrum nutans), and switchgrass (Panicum virgatum). Native forbs are commonly included in seed mixes to benefit wildlife and pollinators. Although highly beneficial to wildlife, these sites generally lack the diversity of species in the Reference State.

Depending on the management objectives of the landowner, cool-season grasses are also feasible. The most common cool-season grasses are non-native species, such as reed canarygrass (Phalaris arunidinacea) and Kentucky bluegrass (Poa pratensis). Although cool-season grasslands are not as species rich or biologically diverse as warm-season grasslands, they still offer various soil health benefits and some ecological benefits for grassland bird species.

Resilience management

Disturbance management and harvest management are resilience management practices. The maintenance of this state requires that the intensity, frequency, duration, and timing of agricultural practices (disturbances) be managed to control or modify vegetation structure.

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