Invasive Exotic Plant Monitoring at Golden Spike National Historical Park

Rush skeletonweed (Chondrilla juncea).
Photo by Steve Dewey, Utah State University, Bugwood.org.

What Are Invasive Exotic Plants?

Invasive exotic plants (IEPs) are species whose introduction to an environment “does or is likely to cause economic or environmental harm or harm to human health.” In national parks, IEPs can alter ecosystems at multiple scales—threatening wildlife, natural landscapes, and recreational opportunities.

IEPs are able to reproduce prolifically, rapidly colonize new areas, and displace native species. Invasive plants fill different ecological roles than the native plants they replace, leaving gaps in the system. In the absence of the native plants, the needs of species that depended on the native vegetation may go unmet, potentially creating a cascade of ecological effects.

The good news is that if discovered before they have a chance to take hold, IEP populations can be eradicated from parks. Small populations are cheaper and easier to control than large populations. Therefore, early detection is critical.

What Can Be Done?

To help park managers identify IEPs and prioritize control efforts, the Northern Colorado Plateau Network (NCPN) monitors invasive exotic plants in eight National Park Service units. First, network and park staff create a list of priority IEPs for each park. Then, on a rotating schedule, a field crew visually surveys for those IEPs along established monitoring routes. Along the routes, they stop and set up plots for additional data collection. The plot data allow network ecologists to estimate trends over time.

Recent Monitoring

During monitoring on June 24–25, 2021, a total of 16 different IEP species were detected along 20 kilometers (12.4 mi) of 13 monitoring routes and transects at Golden Spike National Historical Park. Of these, six were priority species that accounted for 191 separate patches. Three additional IEP species were recorded only in transects.

Invasive exotic plant patches detected along monitoring routes at Golden Spike National Historical Park, June 24–25, 2021. Click to enlarge image.

• IEPs were most dense along the Hydro 1 and Last Cut drainages, followed by the Residence Service Road, East Tour Road, and Visitor Center Sidewalk Area.
• Rush skeletonweed (Chondrilla juncea) was the most prevalent priority species, representing 46% of all recorded patches.
• Field bindweed (Convolvulus arvensis) and Scotch thistle (Onopordum acanthium) constituted most other patches.
• Cheatgrass (Bromus tectorum), crested wheatgrass (Agropyron cristatum), and tumble mustard (Sisymbrium altissimum) were present in 84%, 45%, and 36% of all transects, respectively.
• Broad-leaf pepperwort, dyer’s woad, and moth mullein were all detected in fewer than 10 patches in 2021. These species are good candi­dates for control due to the infrequent num­ber of patches.
• Russian knapweed was not detected in 2021, demonstrating the success of past control efforts on this species.

Invasive exotic plants recorded at Golden Spike National Historical Park, 2021.

Scientific name	Common name	Priority species?
Chondrilla juncea	rush skeletonweed	Yes
Convolvulus arvensis	field bindweed	Yes
Isatis tinctoria	dyer’s woad	Yes
Lepidium latifolium	broad-leaf pepperwort	Yes
Onopordum acanthium	Scotch thistle	Yes
Verbascum blattaria	moth mullein	Yes
Agropyron cristatum	crested wheatgrass	Transects only
Bromus tectorum	cheatgrass	Transects only
Sisymbrium altissimum	tumble mustard	Transects only
Aegilops cylindrica	jointed goatgrass	No
Bromus diandra	ripgut brome	No
Cynodon dactylon	Bermuda grass	No
Cynoglossum officinale	common hounds-tongue	No
Hyoscyamus major	black henbane	No
Lactuca serriola	prickly lettuce	No
Tamarix sp.	tamarisk	No

IEPs Over Time

• When compared to 2018, there was a dramatic increase in the number of IEP patches in 2021, driven by rush skeletonweed and field bindweed. The spread in these two species has been widespread and rapid; for both species, more than 30% of patches are larger than 40 m².
• Rush skeletonweed may have increased due to excellent growing conditions in 2020, when the Northern Rocky Mountain Invasive Plant Management Team did not conduct control efforts due to covid-19.
• Percent frequency of cheatgrass, crested wheatgrass, and tumble mus­tard has not changed dramatically across sampling years. But overall, these species remain widespread.

Past Findings

Invasive Exotic Plant Monitoring at Golden Spike National Historical Park, 2018

Future Work

Seven non-priority species were detected in 2021 (see table). The network will review the priority list for 2023 based on these observations and park concerns. Network staff will return for an eighth year of monitoring in 2023.

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Information in this article was summarized from D.W. Perkins, Invasive Exotic Plant Monitoring at Golden Spike National Historical Park: 2021 Field Season.

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