Sands

Description

The Reference State represents the natural range of variability that dominated the dynamics of this ecological site (ES). This state was dominated by warm-season grasses with cool-season grasses subdominant. In the time before settlers from Europe arrived, the primary disturbance mechanisms for this site in the Reference condition included periods of fluctuating amounts of precipitation, sporadic fire, and herbivory by insects and large ungulates. Frequent surface fires (every 3 to 5 years) and grazing coupled with weather events dictated the dynamics that occurred within the natural range of variability. The less grazing-tolerant tall warm-season grasses and cool-season grasses would have declined. Prairie sandreed would have increased with ongoing disturbance. Today, a similar state can be found on areas that are properly managed with grazing and prescribed burning, and sometimes on areas receiving occasional short periods of rest.

Submodel

Description

The Native/Invaded State represents the more common range of variability that exists with higher levels of grazing management but in the absence of periodic fire due to fire suppression. This state is dominated by warm-season grasses with cool-season grasses subdominant. It can be found on areas that are properly managed with grazing and prescribed burning and sometimes on areas receiving occasional short periods of rest. Grazing tolerant species will increase with disturbance.

Submodel

Description

The invaded state is a result of encroachment mainly by invasive introduced cool-season grasses. The ecological processes are not functioning, especially the biotic processes and the hydrologic functions. The introduced cool-season grasses cause reduced infiltration and increased runoff. 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. The opportunity for high-intensity spring burns is severely reduced by early green-up and increased moisture and humidity at the soil surface and grazing pressure cannot cause a reduction in the dominance sodgrass . Production is limited to the sod-forming species. Infiltration continues to decrease and runoff increases, energy capture into the system is restricted to early season low-producing species. Nutrient cycling is limited by the rooting depth of the dominate species.

Submodel

Description

The conifer/Invaded State is dominated (canopy exceeds 20 percent of total surface area) by areas where trees have become established or have encroached onto the site due to the absence of periodic fire. This state is dominated by eastern redcedar or Rocky Mountain juniper with cool-season grasses subdominant. The plant community can develop into a closed canopy that impedes the reproductive capability of the major native perennial grass species. A single eastern redcedar tree with a crown diameter of seven feet eliminates the equivalent of three pounds of forage. Further, the forage potential of a pasture with 250 mature eastern redcedar trees per acre (or one tree every 13 feet) is reduce by 50 percent. It is suggested that reducing stocking rates by ten percent for every 50 trees per acre. The increase in tree canopy which is a result of a disruption of the natural- and human-related fire regimes that occurred prior to settlement by Europeans, which kept trees from encroaching into much of the grasslands.

Submodel

Description

The Crop Production State is characterized by the production of annual crops using a variety of tillage and cropping systems along with management practices.

Submodel