Invasive exotic plant monitoring in Zion National Park: 2016 field season

Perkins, Dustin

Invasive exotic plant (IEP) species are a significant threat to natural ecosystem integrity 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 10 monitoring protocols to be implemented as part of its long-term monitoring program. NCPN conducted surveys on June 17–24, 2015, and June 1–6, 2016, which represented the completion of the second monitoring rotation at Zion National Park. Over the course of the rotation, NCPN staff detected 271 patches of eight priority IEP species along 161 miles (259 km) of monitoring routes and transects at Zion National Park. Bulbous bluegrass (Poa bulbosa), Scotch thistle (Onopordum acanthium), little bur-clover (Medicago minima), Bermudagrass (Cynodon dactylon), and Johnsongrass (Sorghum halepense) were the most commonly detected priority invasive plants. The highest numbers of priority infestations were found at the Upper Kolob Terrace Road (5.78/km), Watchman Campground and Visitor Center area (4.55 infestations/km), Northgate/Wildcat Trails (2.82/km), Watchman Housing and Parks Transportation, Inc. (2.18/km), South Campground and Nature Center (1.94/km), Oak Creek and Administrative area (1.79/km), and Visitor Center Trails (Archaeology, Museum, Pa’rus, and Watchman) (1.18/km). Patch densities were generally higher on roads than on trails. Ten trails or groups of trails were free of priority IEP patches. IEPs were found on 265 transects (52% of all transects monitored). However, almost all of these detections were cheatgrass (Bromus tectorum). Cheatgrass was widespread—present in 50% of transects and with an estimated cover of 0.97% across all transects sampled. Cheatgrass cover was as high as 2.07% along the Zion Scenic Drive and 2.05% along the Sand Bench Trail. In areas that were sampled in 2012–2013 and 2015–2016, parkwide declines in Johnsongrass and Siberian elm were observed, while increases occurred for Scotch thistle. The largest declines were observed along the Central Trails (-83%), Zion Scenic Drive (-80%), and the Lower Kolob Terrace Road (-75%). The largest percent increases in number of invasive patches occurred at the Visitor Center Trails (+247%), Oak Creek and Administrative Area (+179%), Northgate Peaks/Wildcat Trails (+84%), and Upper Kolob Terrace Road (+76%). NCPN will return to Zion in 2018 to begin the third rotation of invasive plant monitoring.

Invasive exotic plant monitoring in Zion National Park: 2016 field season

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