The invasion of exotic annual grasses is a widespread problem across the western United States. Of particular concern is cheatgrass (Bromus tectorum), which produces continuous mats of fine, highly flammable vegetation that can drive wildfires. To identify persistent and dense coverage of cheatgrass across Canyon County in southeastern Utah, the Canyon Country Fuels Program built a district-wide model based on previous research that sought to Detect Early Season Invasives (DESI). The model uses Landsat imagery to identify areas where vegetation greens up in early spring and is dry by early summer, which is a pattern typical of cheatgrass phenology and in contrast to perennial grasses. The model was based on similar research conducted through a NASA Space Grant Consortium Research Fellowship (https://digitalcommons.usu.edu/spacegrant/2017/Session4/5/) that looked strictly at national parks in southeastern Utah. Expanding the scope to include a wider geographic and administrative range helps agencies like the BLM monitor and adaptively manage areas where cheatgrass is likely dominant. The broad range of ecozones in the extent of the model does result in false positives of DESI, particularly in riparian and agricultural zones. Nonetheless, DESI enables the rapid monitoring of large areas that would be difficult to cover with ground-based surveys, allowing managers to identify regional patterns and distributions of invasive cheatgrass.
https://www.usgs.gov/publications/desi-detection-early-season-invasives-software-installation-manual-and-users-guide, https://digitalcommons.usu.edu/crc_research/429/
A model of cheatgrass distribution in the northern Canyon Country District, Utah. Detect Early Season Invasives (DESI) indices from the previous 5 years were aggregated and superimposed on hazardous fuels reduction projects. Such products allow the fuels program to monitor and ensure that projects are meeting vegetation goals.