PARENT SESSION
Poster Session #20: Arid Lands Restoration.
Tuesday, August 6. Presentation from 5:00 PM to 6:30 PM. Exhibit Hall B & C, TCC

Effects of weed control treatments on restoration of coastal sagescrub vegetation in southern California.

Cox, Robert^*,1, Allen, Edith¹, ¹ University of California, Riverside, Riverside, California

ABSTRACT- Coastal sage scrub (CSS) vegetation in southern California is increasingly the focus of restoration efforts. However, exotic annual grasses (primarily Bromus spp.) and forbs (Erodium spp.) may limit restoration of these areas. In 1999, research was begun to determine how common methods of exotic plant control affect CSS restoration. Weed control treatments were: application of a grass-specific herbicide, thatch removal, and mowing. Cover of exotic and native species was recorded and compared across treatment types. In 2001, after two years of weed control, plots were raked and seeded by hand-broadcasting the seed. Emergence of native seedlings was recorded and compared across treatment types. Application of the herbicide for two consecutive years provided control of exotic grasses even one year after cessation of application. Exotic forbs, however, increased under this treatment. Native forbs emerged best from plots in which thatch was removed and herbicide was applied. Mowing provided some control over exotic grasses but not exotic forbs. Native forbs did not emerge well from the mowing treatment. Native species not included in the seed mix also emerged better in seeded rather than unseeded areas, suggesting that raking alone could be considered as a restoration technique. This research shows that control of exotic grasses may increase densities of exotic forbs, and that thatch removal was the best treatment to increase native forbs.

KEY WORDS: coastal sage scrub, restoration, weed control, Bromus, Erodium