Stony Hills

Description

The Reference State represents what is believed to show the natural range of variability that dominated the dynamics of the Shallow Sandy ecological site prior to European settlement. This site in the Reference State (1.0) is dominated by warm-season grasses and cool-season grasses subdominant. In pre-European times, the primary disturbance mechanisms included frequent fire and grazing by large herding ungulates. Timing and intensity of fires and grazing coupled with weather events dictated the dynamics that occurred within the natural range of variability. Taller warm- and cool-season grasses would have declined and a corresponding increase in short statured grass and grass-like species would have occurred. 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 Shortgrass Sod State (2.0) is dominated by shortgrass species, upland sedges, and shrubs. This State is the result of grazing management that does not provide adequate recovery time for cool-season needlegrass, wheatgrass, and tall and mid-statured warm-season grasses. The hydrologic function of this state is dramatically altered. Runoff is high and infiltration is low. This State is very resistant to change through grazing management alone.

Submodel

Description

The Conifer State is primally found in the areas that have the White River geological formations such as Slim Buttes. This state occurs when ponderosa pine become established or expand on this site. As conifer canopy cover increases, the herbaceous component will decrease, bare ground increases and pine needles build up and create a duff layer. As competition from herbaceous species decrease, conifers can establish more readily under the canopy. Heavy grazing can contribute to this transition, but it may also occur independently without human influence other than through fire suppression.

The Slim Buttes area is drier than the Black Hills (MLRA 62) where expansive stands of ponderosa pine occur, and pine regenerates readily following fire. MLRA 58D is located on the eastern edge of the ponderosa pine range. MLRA 58D probably does not have consistent climatic conditions necessary for ponderosa pine germination and regeneration. Those conditions may be episodic as they are in the drier American southwest. Regeneration of ponderosa pine in New Mexico, Arizona, and western Nebraska are strongly episodic and the basis of these pulses are at least partly controlled by climate. Ponderosa pine in the Southwest require a warm wet spring and an above-average water supply throughout the year for germination to occur and seedlings to establish. One study from northern Arizona showed a large cohort of ponderosa pine that established within a two-year period between 1919 and 1920 when optimal combination of temperature and precipitation factors occurred. This episodic event was not repeated for 73 years (Savage, M., et al, 1996). Successful establishment of ponderosa pine in the Great Plains is unpredictable and requires a combination of sufficient seed availability, adequate year-long soil moisture, a lack of persistent drought, and no fire that affects seedling survival (Kaye et al., 2010).

The Conifer State on the Stony Hills ecological sites may be limited in extent, especially in those plant communities having a large ponderosa pine component. As high intensity, medium to large sized wildfires occur, these plant communities may become less common as grassland communities replace these woodlands.

Submodel