Site description
We conducted this observational field study at two sites within the
Northern Great Plains steppe ecoregion, an area dominated by temperate
and semiarid mixed-grass prairie (Martin et al. 1999). The first site,
sampled in 2019, is located on private land in a Wyoming
shrubland-grassland ecotone in Converse County, WY (43.30° N, -105.05°
W). The site exists within the southern end of the Northern Great Plains
(an area known locally as the Thunder Basin ecoregion) (Porensky et al.
2018). The second site, sampled from 2020-2022, is located at the Fort
Keogh Livestock and Range Research Laboratory in Custer County, MT,
central in the Northern Great Plains steppe (46.34° N, -105.99° W).
Both semi-arid sites are moderately grazed in the summer. At the Wyoming
site, mean annual precipitation (MAP) is 250-300 mm, with 40-50%
falling in April-June, and mean monthly temperature ranges from -5°C in
December to 22°C in July (Porensky et al. 2018). In Converse County, WY,
annual precipitation in 2019 was 391 mm (NOAA National Centers for
Environmental Information 2022). For the Montana site, MAP is 342 mm,
with ~50% falling in May-June, and mean monthly
temperature ranges from -10°C in January to 24°C in July (Peterson and
Reinhart 2012). In Custer County, MT, annual precipitation in 2020 was
251 mm, in 2021 was 257 mm, and in 2022 was 366 mm (NOAA National
Centers for Environmental Information 2022). Common plant species
include Artemisia tridentata Nutt. ssp. wyomingensisBeetle and Young (Wyoming big sagebrush), Bouteloua gracilis(Willd. Ex Kunth) Lag. ex Griffiths (blue grama), Pascopyrum
smithii (Rydb.) Á. Löve (western wheatgrass), Bromus tectorumL. (cheatgrass), Bromus arvensis L. [Bromus
japonicus ] (field brome), and Vulpia octoflora (Walter) Rydb.
(six-week fescue) (Russell et al. 2017, Porensky et al. 2018).