PARENT SESSION
Oral Session # 99: Late-Breaking Newsworthy Presentations.
Presiding: E Preisser and G Larocque
Friday, August 8. 8:30 AM to 12:00 PM, SITCC Meeting Room 205.
Regional mapping of cheatgrass (Bromus tectorum) in the Great Basin, US.
Bradley, Bethany*,1, Mustard, John1, Tausch, Robin2, 1 Brown University, Providence, RI2 USDA Forest Service, Rocky Mountain Research Station, Reno, NV
ABSTRACT- Accurate identification of the spatial distribution of invasive species is critical for land management and biogeochemical modeling. While remotely sensed data provide a tool for identification of invasive species, (Hunt et al., 2003) previous work has been limited spatially and temporally. Here, we exploit the unique interannual phenology of the invasive annual cheatgrass (Bromus tectorum) expressed in remotely sensed data to map its distribution in the Great Basin, US. Measurements of Normalized Difference Vegetation Index (NDVI) at a 1 km spatial resolution have been made by the Advanced Very High Resolution Radiometer (AVHRR) satellite. We use biweekly NDVI composites from 1989-1999 processed by the USGS. An 11-year average annual NDVI cycle was created for each pixel. The annual average was removed from every year in the time series to create a residual NDVI, which was fit with a line. By mapping the distribution of slopes of lines fit to this residual, anomalous areas within the Great Basin with interannual responses significantly different from the regional mean were detected. Amplified greenness following above average precipitation caused the anomalous response. Past work has shown that invasive annuals exhibit this type of amplified response compared to native perennials (Elmore et al., 2003). Using this technique, we identified and mapped regions with anomalous amplified responses. These included valleys near Winnemucca, NV, south of the Great Salt Lake, and select regions in the Mojave Desert. Field observations near Winnemucca showed that mapped anomalies correspond to areas with high concentrations of cheatgrass. This map shows that cheatgrass dominates at least 15% of valleys near Winnemucca. The high correlation between our map of amplified response and the location of cheatgrass indicates that this remote sensing technique can effectively map the spatial extent of invasive annuals in the Great Basin.
Key words: remote sensing, invasive species, bromus tectorum, great basin