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My research project is exploring the survival and maturation of rabbitbrush and sagebrush in Guerin Creek. Some of the underlying theoretical perspectives I will consider are water availability, interspecies competition, predation (herbivory), and disturbance-succession dynamics.
The water requirements of brush bushes and water availability at the creek site both interact to change germination rate, seedling establishment, and ultimately the maturation of brush bushes (McLendon et al. 2008).
Since both big sagebrush and green rabbitbrush bushes live together, they are in direct competition for space (access to sunlight), access to water sources, and pollinators (Young and Evans 1974). When examining my study area, there were clearly more big sagebrush than rabbitbrush in the creek valley. This was confirmed when analyzing my data and suggests that sagebrush is better adapted to life in the creek valley.
These two species are also subject to predation. Predators are similar between the two brush bushes including insects, grazing animals and rodents (Johnson 1979). Differential predation could influence the successful maturation of both brush plants, however in the literature I have reviewed, the predators are very similar for both plants. Because the brush bushes are extremely aromatic, most undulates do not graze on them, herbivores like deer and cattle are more likely to eat sagebrush over rabbitbrush, but consuming either in excess leads to significant decline in digestion.
Rabbitbrush is known to invade established sagebrush habitat following a disturbance such as a wildfire or construction, as it is much faster to grow from its underground roots (Young and Evans 1974). Sagebrush establishes more gradually following the disturbance. Research on the pre- and post-disturbance climax communities suggest that invasive grasses and plants lead to a significantly different composition in terms of vegetation following a disturbance. Because I was only able to see the mature plants, the species composition of the Guerin Creek ecosystem could not be measured.
Some interesting notes in performing the literature review for my project, I have found the research lacking specifically when looking at the water requirements for the brush bushes. In the reading I have completed, sagebrush and rabbitbrush are often considered pests, despite their significant ecological role in the stage-steppe ecosystems.
Keywords: Artemisia tridentata, depth to water (DTW), desert ecozone
References
Johnson, M. K. 1979. Foods of Primary Consumers on Cold Desert Shrub-Steppe of Southcentral Idaho. Journal of Range Management 32:365–368.
McLendon, T., P. J. Hubbard, and D. W. Martin. 2008. Partitioning the use of precipitation- and groundwater-derived moisture by vegetation in an arid ecosystem in California. Journal of Arid Environments 72:986–1001.
Young, J. A., and R. A. Evans. 1974. Population Dynamics of Green Rabbitbrush in Disturbed Big Sagebrush Communities. Journal of Range Management 27:127–132.
