Action: Apply herbicide and sow seeds of shrubland plants to control grass
- One randomized, controlled study in the USA found that areas where herbicide was sprayed and seeds of shrubland species were sown had more shrub seedlings than areas that were not sprayed or sown with seeds.
- One randomized, replicated, controlled study in the USA found that spraying with herbicide and sowing seeds of shrubland species did not increase the cover of native plant species, but did increase the number of native plant species.
- One of two studies in the USA found that spraying with herbicide and sowing seeds of shrubland species reduced non-native grass cover. One study in the USA found that applying herbicide and sowing seeds of shrubland species did not reduced the cover of non-native grasses
Applying herbicide may help to control problematic grass species while sowing seeds may help shrubland plant species become established.
Supporting evidence from individual studies
A randomized, controlled study in 1997–1999 in sagebrush scrub habitat that had been invaded by grass and burnt by wildfires in California, USA (Cione et al. 2002) found that spraying invasive grasses with herbicide followed by sowing of shrub seeds increased the seedling abundance of shrub species and reduced grass cover. After one year, areas where grasses were sprayed with herbicide and sown with seeds had more shrub seedlings (1–29 seedlings/m2) than unsprayed areas (0 seedlings/m2). Additionally, grass cover in areas where invasive grasses were sprayed with herbicide was lower (3%) than in unsprayed areas (84%). In 1997–1998 grass was sprayed with herbicide, and shrub seeds were subsequently sown in five randomly located 5 x 5 m plots, while in five other plots herbicide was not used and no seeds were sown. In spring 1997 plots were surveyed for grasses using two 0.25 m x 0.5 m quadrats/plot and two 0.5 m x 1 m quadrats/plot for shrubs.
A randomized, replicated, controlled study in 2005–2006 in sagebrush scrub habitat, dominated by non-native grasses in the USA (Marushia & Allen 2011) found that sowing seeds, followed by spraying with herbicide did not reduce the cover of non-native species nor did it increase the cover of native species, but it did increase the number of native plant species. In areas that were seeded and sprayed with herbicide, cover of non-native plant species (40%) was not significantly different from areas that had been seeded but not sprayed with herbicide (63%). Native species cover was also not significantly different in areas that had been seeded and sprayed with herbicide (40%) compared to areas that had been seeded but not sprayed (cover 24%). However, areas that were seeded and sprayed with herbicide had a higher number of native plant species (7 species) than areas that were seeded but not sprayed (5 species). In 2005 five 5 m2 plots were sown with seeds of shrubland species and sprayed with herbicide, while five other plots were sown with seeds but not sprayed with herbicide. Plant cover was measured in a 0.5 m2 quadrat placed in each plot.
- Cione N.K., Padgett P.E. & Allen E.B. (2002) Restoration of a Native Shrubland Impacted by Exotic Grasses, Frequent Fire, and Nitrogen Deposition in Southern California. Restoration Ecology, 10, 376-384
- Marushia R.G. & Allen E.B. (2011) Control of Exotic Annual Grasses to Restore Native Forbs in Abandoned Agricultural Land. Restoration Ecology, 19, 45-54