A comparison of managment methods and restoration treatments for the invasive grass, Ehrharta erecta
Ehrharta erecta Lam. (panic veldt grass) is an invasive species introduced to the Santa Cruz Mountains in 1964. Since its introduction, E. erecta has become a common invader in disturbed areas, as well as oak and mixed evergreen woodlands. Little is known about the impacts of E. erecta on native species. Though frequently managed with chemical and mechanical methods, the efficacy of these methods at removing E. erecta has not previously been rigorously tested. In 2m x 2m experimental plots on the campus of the University of California, Santa Cruz, we quantified the effectiveness of hand pulling and herbicide application on E. erecta removal for a period of two years, as well as the response of the native plant community to E. erecta removal. We also tested whether planting seedlings of the native understory forb, Clinopodium douglasii (Benth.) Kuntze, in invaded sites promoted restoration and reduced E. erecta re-invasion.
While both management methods were effective at removing E. erecta relative to a control, 2 years following treatment, re-invasion was greater in sites where E. erecta was manually removed compared with herbicide removal. Native cover was reduced in herbicide-treated plots compared with manual removal plots. Planting of C. douglasii increased native plant cover in all sites, however it did not significantly affect the efficacy of either removal treatment. The results of this research demonstrate that E. erecta can be effectively managed using manual and chemical removal methods, as well as will allow land managers to better plan native understory restoration efforts.