Upland Loam (basin big sagebrush)

Description

The Reference State is a description of this ecological site just prior to Euro-American settlement but long after the arrival of Native Americans. The description of the Reference State was determined by NRCS Soil Survey Type Site Location information and familiarity with rangeland relict areas where they exist. The Reference State for this site would have been characterized as a shrub steppe co-dominated by basin big sagebrush (Artemisia tridentata ssp. tridentata), the dominant shrub, and having a rich herbaceous understory. The proportions of shrubs and herbs would have been dependent upon the length of time elapsed since the last wildfire or other sagebrush-killing event. If fire had not occurred within the past 30 years (1.2a), basin big sagebrush would have been the dominant shrub, having a native perennial herbaceous understory (1.1). If less than 10 years had elapsed since the last fire (1.1a), perennial native herbs would have increased and the shrub component would have been dominated by root-sprouting species such as rubber rabbitbrush (Ericameria nauseosa), yellow rabbitbrush (Chrysothamnus viscidiflorus) and spineless horsebrush (Tetradymia canescens) (1.2). Soil anoxia from extremely wet years or an outbreak of Aroga (Aroga spp.) moth (1.1b) could have also reduced sagebrush and enhanced root-sprouting shrubs and perennial herbs (1.2) in some years. The same effect would have also been achieved by parch blight due to lack of snow cover during dry, cold winters (1.1c). A more complete list of species by lifeform for the Reference State is available in the accompanying tables in the “Plant Community Composition by Weight and Percentage” section of this document.

Submodel

Description

State 2 is very similar to State 1 in form and function, with the exception of the presence of non-native plants and animals, possible extinctions of native species, and a different climate. State 2 is a description of the ecological site shortly following Euro-American settlement. This State can be regarded as the current potential. As with State 1, a shift will be seen in the abundance of basin big sagebrush relative to the perennial herbs based upon the amount of time that has elapsed since the last wildfire or other sagebrush-killing event. Wildfire (2.1a) will temporarily remove basin big sagebrush, allowing root-sprouting shrubs and all types of herbs (both native and non-native) to increase (2.2). Lack of fire (2.2a) will favor the return of basin big sagebrush provided that there is adequate seed source from adjacent unburned areas. Perennial native herbs and non-native annuals will maintain their presence post-fire. Other drivers that could reduce sagebrush and favor root-sprouting shrubs (2.2) include anoxic soils from extremely wet years, outbreaks of Aroga moth (2.1b), or parch blight due to lack of snow cover during dry cold winters (2.1c). The resiliency of this State is maintained by a healthy, productive, and diverse plant community that can provide native seed sources and promotes soil stability, water infiltration, and soil moisture retention. The resiliency of this State can be maintained by reducing livestock grazing impacts, especially during the growing season of perennial herbs. Conversely, continued heavy grazing will negatively impact the resiliency of this State.

Submodel

Description

With multiple-year heavy livestock grazing, especially during the growing season, native perennial herbs are diminished. Once the soil seed reserve is exhausted, there is little opportunity for recovery. In the absence of fire (3.2a) basin big sagebrush will begin to dominate (3.1). Where mechanical or fire damage occur to the non-sprouting basin big sagebrush (3.1a), root-sprouting shrubs can increase (3.2). The state is maintained by the lack of a healthy, productive and diverse herb component capable of providing native seed source, soil stabilization, and soil moisture retention.

Submodel

Description

The most common seedings of the past have been to Eurasian wheatgrasses (Agropyron spp.) or ryegrasses (Elymus spp.) (4.1). Where tillage has been employed, the native forbs and browse have most likely been destroyed. Thus, if a more diverse plant community is required (4.2), other species will have to be added to the seed mix and utilization by livestock deferred for several years (4.1a). In some circumstances, the native forbs and shrubs will slowly re-establish (4.2 and 4.3) when adjacent area have not been tilled. Subsequent re-treatment with herbicide or mechanical (e.g. Lawson pasture-aerator) action (4.2a and 4.3a) will be necessary to maintain grass dominance (4.1). Fortunately, annual invaders such as cheatgrass are short-lived where Wasatch Formation-derived soils (MLRA 47A) or the Gilbert Land Surface (MLRA 47C) are involved, both being of nutrient-poor parent materials. Once a site is re-established with forbs and shrubs (4.2) and a sufficient length of time has elapsed since the last fire (4.2b), pioneering shrubs such as snakeweed, rubber rabbitbrush, and yellow rabbitbrush may dominate the site (4.3). Returning to a more diverse plant community (4.2) may require mechanically removing some shrubs and re-seeding (4.3b). This State can be maintained by moderate levels of livestock use or alteration of dates of use, particularly during the boot stage of the grass. Heavy spring use by livestock will reduce the resiliency of this State.

Submodel