Sandy

Description

This State represents what is believed to show the natural range of variability that dominated the dynamics of the ecological site prior to European settlement. This site in Reference, is dominated by warm-season grasses and sub-dominant cool-season grass. Grazing or the lack of grazing and fire are the major drivers between plant communities. Non-use and no fire or long-term, light grazing will result in heavy litter accumulations and the invasion of non-native, cool-season grasses.

Submodel

Description

The Shortgrass State is dominated by grazing tolerant, shortgrass species and upland sedges. This State is the result of grazing patterns that do not provide adequate recovery time for the tall, warm-season and mid stature cool-season grasses. The hydrologic function of this site is dramatically altered. Runoff is high and infiltration is low. This State is very resistant to change through grazing management alone.

Submodel

Description

This state is the result of invasion and dominance of introduced species. This state is characterized by the dominance of Kentucky bluegrass and/or smooth brome, and an increasing thatch layer that effectively blocks introduction of other plants into the system. Plant litter accumulation tends to favor the more shade tolerant, introduced grass species. The nutrient cycle is also impaired, the result is typically a higher level of nitrogen which also favors the introduced species. Increasing plant litter decreases the amount of sunlight reaching plant crowns thereby shifting competitive advantage to shade tolerant, introduced grass species. Studies indicate that soil biological activity is altered, and this shift apparently exploits the soil microclimate and encourages growth of the introduced grass species. Once the threshold is crossed, a change in grazing management alone cannot cause a reduction in the invasive grass dominance. Preliminary studies would tend to indicate this threshold may exist when Kentucky bluegrass exceeds 30 percent of the plant community and native grasses represent less than 40 percent of the plant community composition. Plant communities dominated by Kentucky bluegrass have significantly less cover and diversity of native grasses and forb species (Toledo, D. et al., 2014).

Submodel

Description

This State can transition from any Plant Community. The two separate vegetative Plant Communities are highly variable in nature. They are derived through different management scenarios, and are not related successionally. Infiltration, runoff, and soil erosion varies depending on the vegetation present on the site.

Submodel