Environmental Change in the Great Basin: Tracking Cheatgrass Invasion with Remote Sensing

Land use legacies of ecosystem disturbance (eg. grazing, agriculture) in the Great Basin, US have been shown to enhance the spread of invasive species, in particular cheatgrass (Bromus tectorum) (Figure 1). Cheatgrass is a critical problem in the west because its presence changes ecosystem function, leads to increased fire frequency, and creates unpalatable rangeland for livestock. We identify the regional extents of cheatgrass invasion by identifying cheatgrass based on its unique, interannual amplified response to rainfall using Advanced Very High Resolution Radiometer (AVHRR) time series (Figure 2). Areas with extensive invasions occur in northern Nevada, near the Humboldt River, and in central Utah, near the Bonneville salt flats (Figure 3). We then scale down to a Landsat time series in the highly invaded area of northern Nevada to understand the process of cheatgrass invasion over the last 30 years. Landsat data show that current invasion is primarily driven by fire, which destroys native shrubs and clears the way for cheatgrass establishment. However, cheatgrass is also spreading extensively via windblown dispersion. Characteristics of the ecosystems into which cheatgrass is able to spread most readily will help us to improve land management techniques to slow invasion.

Figure 1: Photographs of a native shrub/bunch grass ecosystem (left) and a cheatgrass monoculture (right).

Figure 2: AVHRR time series of a native ecosystem (black) and a cheatgrass dominated ecosystem (green) show that cheatgrass has an amplified response to rainfall.

Figure 3: A regional map of amplified response in the Great Basin shows the likely distribution of cheatgrass dominated ecosystems. Cheatgrass dominance is concentrated in northern Nevada and central Utah.

Ecology and Evolutionary Biology | Environmental Change Initiative | Environmental Studies | Geological Sciences | Marine Biological Laboratory | Watson Institute

Last updated 10/20/04

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