Study design
During the summer of 2019 in Wyoming, we established 5 blocks each forB. arvensis and B. tectorum along 10 natural invasion gradients. Each block consisted of 5, 1 m2 plots with different invasion levels (1 – very low, 2 - low, 3 - moderate, 4 - high, and 5 – very high cover) of either B. arvensis or B. tectorum (50 total plots). During the summer of 2020 in Montana, we established blocks along 8 natural invasion gradients of B. arvensis only. Each block consisted of 6, 1 m2 plots across 3 levels of invasion abundance (1- very low, 3 – moderate, 5 – very high cover) by B. arvensis . In 2020, we collected data from a total of 48 plots, but in 2021 and 2022, we only present data from half (24) of these plots as the other plots were allocated for an additional treatment not presented here. At both sites, invasion levels represent aerial cover categories of the invasive compared to the rest of the plant community.