Rolling Sands

Description

The Grassland State is supported by empirical data and is defined by two native plant communities that are a result of periodic fire, drought, herbivore, and ungulate grazers. These events are part of the natural disturbance regime and climatic process that contribute to the development of the site. The Reference Plant Community (1.1) consists of tall, mid, short, warm and cool-season grasses, forbs and shrubs. This plant community is dominated by tall and mid, warm-season grasses (65 percent composition by weight). The Midgrass-shortgrass, Increased Sand Sagebrush Plant Community (1.2) is dominated by blue grama, sand sagebrush, and little bluestem and is vulnerable to exceeding the resilience limits of the Grassland State and transitioning to the Shrub State .

A loss of plant cover and an increase in bare ground creates the probability of wind erosion. Drought-induced wind scouring coupled with disturbance (fire, continuous grazing, rodents, or vehicle traffic) can lead to blowouts and possibly an active dune. Extreme care should be taken when managing these areas. Ongoing field investigations and evaluations are necessary to assess the ecological communities in regard to resilience and changes in vegetation, soil, and hydrology of the site.

These plant communities may not represent every possibility, but they are the most prevalent and repeatable plant communities that exist on this ecological site. The plant composition table shown below has been developed from the best available knowledge at the time of this revision.

Submodel

Description

The Shrub State is supported by empirical data and is defined by one plant community phase.
The Reference Grassland State ecosystem has been driven beyond the limits of ecological resilience and has crossed a threshold into the Shrub State. The designation of the Shrub State denotes changes in plant species composition. This change in plant species negatively affects hydrology, forage production, and wildlife habitat, and increases erosion potential. Understory plants may be negatively affected by shrubs reducing the availability of light, soil moisture, and soil nutrients. As the size and density of shrubs increase, the cover and productivity of understory plants decrease. Desirable forage grasses are often the most severely reduced (Eddleman, 1983). As the vegetative cover changes from grasses to shrubs, more precipitation is lost via evaporation; therefore, less precipitation is available for producing herbaceous forage or for deep drainage or runoff (Thurow and Hester, 1997).

As shrubs increase, fine-fuel loads decrease. When shrub canopy increases to greater than 30 percent, significant biotic and soil changes have negatively impacted energy flow and the nutrient and hydrologic cycles. The processes and functions have shifted to favor the Shrubland State. Prescribed fire may become an ineffective tool to eradicate or decrease the shrubs due to the lack of fine fuel loads.

This alternative state should be tested through long-term observation of ecosystem behavior and repeated application of conservation and restoration practices.

Submodel

Description

The Reference Grassland State ecosystem has been driven beyond the limits of ecological resilience and has crossed a threshold into the Tillage State. The designation of the Tillage State denotes changes in infiltration, runoff, bulk density, aggregate stability and species composition. The changes in inherent soil properties, water movement and the plant community affect changes in hydrologic functionality, biotic integrity, and soil and site stability.

The Tillage State includes two community phases that are highly variable. These communities are derived through two distinct management scenarios and are not related successionally. Infiltration, runoff, and soil erosion vary depending on the vegetation present.

The Tillage State consists of abandoned cropland that has been naturally revegetated (go-back) or reseeded. Many were planted with a local seeding mix under the Conservation Reserve Program (CRP), or were planted to a monoculture of sideoats grama. Go-back communities are difficult to define due to the variability of plant communities that exist. Many of these communities are represented by threeawn species.

The Tillage State is an alternative state because the ecological functions, i.e. dynamic soil properties and plant communities, are not fully restored to that of the Grassland State. Tillage can destroy soil aggregation, which is an example of dynamic soil property change. Aggregate stability is critical for infiltration, root growth, and resistance to water and wind erosion (Brady and Weil 2008).

This alternative state should be tested through long-term observation of ecosystem behavior and repeated application of conservation and restoration practices.

Submodel