The sagebrush biome: A look at the past.
Miller, Rick*,1, 1 Oregon State University, Corvallis, OR
ABSTRACT- The sagebrush biome extends from the east slopes of the Cascades and High Sierras to the Rocky Mountains occupying 40 million ha of the American West. This large biome crosses various geologic regions, climatic boundaries, and varying topography. Artemisia species are usually found in areas where precipitation is greater than 178 mm and between elevations of 150 to 3,300 m. Since Eurasian settlement in the late 1800s this biome has been undergoing rapid change with estimates of 1/3 having been converted to cultivation, invaded by exotic weeds, and impacted by conifer encroachment. The rapid rate of decline is likely unprecedented from past changes. However, this biome has been dynamic in both time and space since the end of the Pleistocene era. During the Holocene, short and long term fluctuations in climate, fire, floods, and volcanic eruptions have maintained this biome in a continual state of change. Salt deserts and sagebrush steppe communities have expanded and contracted inversely with grass dominated communities. In cool, wet periods fuels accumulated in this generally fuel limited ecosystem, leading to more frequent fires across the region. During the mid Holocene, a relatively dry warm period (8,000 and 4,000 years BP), the salt deserts expanded, sagebrush dominance increased, and herbaceous cover decreased resulting in a decline of ground cover. Many Native American caves in the Great Basin were abandoned and large amounts of soils were redistributed across the region during this period. The most recent shift in climate has been a general warming since the end of the Little Ice Age (700 to 150 years BP). This shift in warming coincides with the introduction of exotic plant species, livestock grazing, altered fire regimes, and the rapid urbanization of the West.
Key words: fire, sagebrush, climate
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