Plant Communities, Ethnoecology, and Flora of the Idaho National Engineering Laboratory

Anderson, Jay; Ruppel, Kristin; Glennon, James; Holte, Karl; Rope, Ronald

The Idaho National Engineering Laboratory (INEL) occupies 2,300 km2 of sagebrush steppe on the eastern Snake River Plain and is the largest of the few protected reserves of this extensive vegetation type. This publication documents the floristic diversity of the area, describes its abiotic environment and common plant communities, and summarizes our expanding knowledge of its ethnoecology. The INEL lies in the rainshadow of mountain ranges immediately to the west. Mean annual precipitation is about 220 mm, and the scarcity of water coupled with cold winters and hot, dry summers places severe constraints on plant growth. Nevertheless, the INEL proper is home to some 400 species of vascular plants. Compared with areas that have a long history of livestock grazing, the INEL supports a rich diversity of native forbs. Eighty-five percent of the species are natives, and three-fourths ofthose are forbs. The natural vegetation of the INEL typically consists ·of an overstory of shrubs and an understory of grasses and forbs. Big sagebrush (Artemisia tridentata) is by far the most common shrub, but 43 other species of shrubs have been recorded on the INEL and the adjacent Big Southern Butte. Perennial grasses are the most abundant understory plants in shrub-dominated communities and are the dominant plants in grassland communities where shrubs are scarce. Ten vegetation/cover classes are described and depicted on the enclosed vegetation map. Prior to irrigation development in adjacent valleys, the area now within the INEL boundaries was the final destination of three important perennial streams, the Big Lost River, the Little Lost River, and Birch Creek. These streams emptied into playas and sinks on the floor of the 90 km2 area occupied during the Pleistocene by Lake Terreton. Although difficult to imagine given the current flows in the Big Lost River, landform remnants of a Pleistocene flood through Box Canyon on the INEL's west side implicate that flood as the third most powerful known. Humans arrived on the eastern Snake River Plain about 11,000 years ago. Over 850 archaeological sites at the INEL indicated a slow but steady increase in the use of the area over that period. The eastern Snake River Plain's original inhabitants likely were ancestors of the Plateau or Plains cultures who migrated to the north or northeast during the Altithermal, a period of gradual warming and drying during the early to mid Holocene. The ancestors of the present-day Shoshone and Bannock migrated north from the Great Basin proper as conditions became cooler and wetter some 4,500 years B.P. Archaeological sites in the region document continuity of the Shoshonean culture from 4,000 years until historic times. These native peoples primarily were hunters of large game, so the major role of plants was to furnish habitat and food for the animals that attracted the hunters to the area. Direct use of plants by the aboriginal inhabitants is only infrequently indicated by the archeological record, but the artifacts found at one INEL site, Aviator Cave, suggest a variety of uses including foods, fiber, and fuel. Information on known and potential uses of the region's plants by Native Americans is included in a summary table. The fur trade, the Oregon Trail (including Goodale's Cutoff which crossed the southwest comer of what is now the INEL), and the establishment of Fort Hall all impacted the natural ecosystems and aboriginal culture of the eastern Snake River Plain in the early to mid 1800's. Bison were still numerous in the area in 1834, but numbers declined rapidly thereafter. The late 1800's witnessed severe overgrazing by domestic cattle and sheep throughout the Intermountain West, but the extent to which native plant communities on the area now occupied by the INEL were impacted is unknown. Remnants of trails and wagon roads that were used, at least in part, for cattle and sheep drives indicate that the area was grazed