Invasion gradients
Selected plots yielded invasion gradients in Montana and Wyoming forB. arvensis and B. tectorum (Appendix S1: Figure S1, S2).
Absolute percent cover of bromes significantly increased with relative
percent cover across all three gradients (Montana B. arvensis :
F1, 43 = 940.4, p < 0.0001; Wyoming B.
arvensis : F1, 23 = 1034, p < 0.0001; WyomingB. tectorum : F1, 23 = 161.2, p <
0.0001) (Appendix S1: Figure S1). Further, at invasion levels 1, 2, and
4, we saw no difference in cover between B. arvensis and B.
tectorum . We found site level differences in B. arvensis cover
at invasion level 3; we only saw differences in cover between B.
arvensis and B. tectorum at invasion level 5 in Wyoming
(Appendix S1: Figure S2).