Monitoring & Treatment of Invasive Plants at Water Systems

This article was originally published in The Midden – Great Basin National Park: Vol. 17, No. 2 , Winter 2017.

A rosette of a bull thistle. This early growth is monitored and treated by the invasive plant team in the park.

NPS Photo by M. Horner

By Julie Long, Biological Science Technician

At Great Basin National Park, four meadow complexes provide drinking water to visitors, park residences, and campgrounds. Wet meadows make up only 0.1% (87 acres) of the park, varying in elevations from 7,200 to 10,300 feet. These mesic habitat types seem more susceptible to invasion by non-native plant species due to available water and soil conditions. Invasive plants can alter fire regimes and outcompete native plant populations that are already adapted to the soil and surrounding habitat. This poses a threat to native plant communities, impacts forage for wildlife, and degrades soils.

Sites at Cave Springs, Baker Creek, Lehman Creek, and Wheeler Peak serve as collection sources for potable water, allowing manual (grubbing or pulling by hand) treatments on invasive plant species as the only appropriate mode of treatment. Use of herbicide treatments in these areas is prohibited because of the utilized resource – drinking water. There are over twenty-five non-native plant species in the park, but the four priority species for treatment were bull thistle (Cirsium vulgare), whitetop (Cardaria draba), musk thistle (Carduus nutans), and Canada thistle (Cirsium arvense).

Table 1. The number of acres, visits, and time spent at four water collection sources.

Manual treatments were implemented from May to late September on five acres by two park employees. Four sites were visited twenty-two times and a total of thirty-one hours were dedicated to hand pulling invasive plants (Table 1). Each water source was surveyed in order to remove any invasive plants before they had time to flower or go to seed. The Lehman Creek and Wheeler Peak collection areas had no targeted invasive plant species present while Cave Springs and Baker Creek each had existing bull thistle populations. At Cave Springs a total of 0.2 acres, with about 461 bull thistle plants, were treated, and at the Baker Creek treatment site, six bull thistles were removed.

In order to reduce infestations and prevent the spread of non-native plant species, the park will continue to monitor and treat invasive plant species following integrated pest management practices to protect native plant communities and habitat.