Golden Spike Cultural Landscape Report

Vegetation

Lands included within the boundaries of Golden Spike NHS include remnant stands of the native sagebrush-steppe vegetation, as well as historic and modern ornamental plantings — the latter located principally in the summit area. In addition, lands outside the boundary but within the viewshed of the historic site also contain agricultural vegetation — mostly dry-land farm crops such as winter wheat.

A study conducted by Allen and Curto in 1994 and 1995 indicates that 69 percent of the 121 plant species identified within the park are native to the area; 31 percent of the species are introduced (Allen and Curto: 1995). Although native species significantly outnumber introduced species, the composition of native vegetation stands and dominance of individual species within those stands has changed rather markedly. Today a mixture of shrubby plants including sagebrush, rabbitbrush, broom snakeweed, and a variety of introduced species dominate, replacing the once extensive stands of native grasses. This variation of the sagebrush-steppe vegetation zone is primarily a result of the disturbances caused by intensive grazing and agricultural use.

Promontory Summit

Native Plant Communities

Much of the 160-acres in the block of land owned by the park service in the summit area consists of remnant sagebrush-steppe vegetation, especially the hillslope south of the visitor center. Although historic-era agricultural practices, principally grazing, have altered the distribution and density of native shrubs and grasses, the area retains mixed stands of native shrubs and grasses.

Ornamental Vegetation

Ornamental vegetation is concentrated in the area around the modern visitor center. Ornamental plants include those leftover from the settlement era (1870-1942), when the area was known as Promontory Station, as well as the landscape plantings done by the park service in the vicinity of the parking lot and visitor center.

Extant historic-era ornamental plantings include two box elder trees, both located inside the park boundary (Figure 32). Although box elder is native to the region, these trees were planted by settlers of Promontory Station. Similarly, the ornamental matrimony vine (Lycum barbarum), also locally known by the common names of "pea-vine" or "tea-vine," is an introduced perennial planted by area settlers. Other isolated ornamental plantings include a single Golden Currant (Ribes aureum), located adjacent to the parking lot.

Figure 32. View to east from the vicinity of the Last Spike Site along the reconstructed main line and UP siding (to right). Box elder tree is inside the park boundary. Source: HRA 2000.

The landscape plantings in and around the visitor center consist mostly of native shrubs (including those in the landscape islands within the parking lot and adjacent to the rear of the building). However, patches of lawn occur in front and back of the visitor center, flanking the entrances to the building.

Agricultural Vegetation

Cultivated fields are located on all sides of the 160-acre parcel of park land in the summit area. The predominant crop is winter wheat; some fields are fallow.

West and East Slopes

Native Plant Communities

Vegetation within the existing and authorized park boundary on the west and east sides of the summit consists of remnant sagebrush-steppe vegetation. Relative densities of shrubs versus grasses and forbs vary from site to site. Introduced species dominate in some disturbed areas, such as the unfinished segments of the Union Pacific grade on the west slope, a few of which are covered with cheatgrass (Figure 33).

Figure 33. Looking southwest from west slope auto tour (CP grade) across unfinished UP grade. Note variation in vegetation — shrubs (sage and rabbitbrush) between the grades and cheat grass on the UP grade. Source: HRA 2000.