Established Perennial vegetation provides high resistance to reinvasion by exotic annual grasses

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In this study, exotic annual grass cover and density were greatly reduced in all treatments where perennial seedlings were planted compared with the control (no seedlings planted). Treatments including crested wheatgrass (Agropyron desertorum) generally limited annual grasses more than other treatments. Most notably, forage kochia (Bassia prostata) reduced exotic annual grasses less than crested wheatgrass and crested wheatgrass planted with forage kochia. This suggests that if forage kochia will be planted, it should be used in conjunction with perennial bunchgrasses in efforts to revegetate exotic annual grass − invaded sagebrush steppe. Established native vegetation also greatly reduced exotic annual grass reinvasion. Though some differences existed among established vegetation treatments, our study highlights that established perennial vegetation prevents redomination by invasives after exotic annual grass control.