Invasive exotic plant monitoring at Dinosaur National Monument: 2023 and 2024 field seasons

Nash, Tiffany

doi:10.36967/2313969

Invasive exotic plant (IEP) species are one of the biggest threats to natural ecosystem integri¬ty and biodiversity and controlling them is a high priority for the National Park Service. The Northern Colorado Plateau Network (NCPN) selected the early detection of IEPs as one of 11 monitoring protocols to be implemented as part of its long-term monitoring program. This report represents work completed during the 2023 and 2024 field season at Dinosaur National Monument (UT, CO). From August 16–23, 2023, and June 20–26, 2024, we found a total of 12 different priority IEP species during monitoring. A total of 4,683 IEP patches were recorded along 311.2 kilometers (193.4 miles) of 3 monitoring routes. Park managers can use this report to help prioritize IEP treatment. At Dinosaur National Monument, the NCPN monitors IEPs in the Green and Yampa River corridors. This represents the completion of the fourth monitoring rotation of the entire river corridor (2002–2005, 2010–2011, 2017–2019, 2023–2024). NCPN staff detected 12 priority IEP species and six non-priority species in an 84.6-hectare (209-acre) area along 311.2 kilometers (193.4 miles) of the Green and Yampa Rivers. A total of 4,683 IEP patches were detected. Of those patches, 24.9% were smaller than 40 m2. Tamarisk (Tamarix sp.), broad-leaf pepperwort (Lepidium latifolium), yellow sweetclover (Melilotus officinalis), and Russian knapweed (Acroptilon repens) were the most widespread species. Yellow sweetclover has decreased on all three river reaches during the survey years. Musk thistle (Carduus nutans) was found at considerably lower levels than yellow sweetclover but has increased on the Green River above the confluence, while decreasing on the Green River below the confluence and Yampa River. Leafy spurge (Euphorbia esula) has remained stable on the Green River above and below the confluence and increased on the Yampa River. Cheatgrass (Bromus tectorum) was not monitored in the first rotation but decreased substantially in cover and percent frequency on all three river sections from 2017–2019 to 2023–2024. This increase may be due to recent high-flow scouring events. The highly regulated Green River above the confluence generally has the highest number of IEPs, while the Green River below the confluence has a moderate number of IEPs. The largely unregulated flows of the Yampa River continue to result in a lower number of patches per kilometer, lower percent cover, and lower percent frequency than the Green River above and below the confluence.

Invasive exotic plant monitoring at Dinosaur National Monument: 2023 and 2024 field seasons

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