Action: Cut/mow to control grass and sow seed of shrubland plants
- One randomized, replicated, controlled study in the USA found that the biomass of sagebrush plants in areas where grass was cut and seeds sown did not differ from areas where grass was not cut, but seeds were sown.
- One randomized controlled study in the USA found that cutting grass and sowing seeds increased shrub seedling abundance and reduced grass cover
- One randomized, replicated, controlled study in the USA found that sowing seeds and mowing did not change the cover of non-native plants or the number of native plant species.
Mowing reduces the length of all vegetation. Combined with sowing of seeds this practice may limit the growth of grasses while allowing shrubland plants to become established at grass dominated sites.
Supporting evidence from individual studies
A randomized, replicated, controlled study in 1993–1994 in sagebrush scrub habitat invaded by non-native grasses in California, USA (Eliason & Allen 1997) found that in areas where invasive grasses were cut and seeds of shrubs were sown, the biomass of sagebrush Artemisia californica plants did not differ from areas where invasive grasses were not cut but seeds were sown. In areas where invasive grasses were cut and shrub seeds were sown the biomass of sagebrush individuals (141 g) was not significantly different to those in areas where only shrub seeds were sown (50–119 g). In March 1993 invasive grasses were removed in three 1 m x 1.2 m plots after which sagebrush seeds were sown, while in 12 plots grasses were not removed and seeds were sown. Sagebrush plants were harvested in May-June 1994.
A randomized, controlled study in 1997–1999 in a sagebrush scrub habitat that had been invaded by grass and burnt by wildfires in California, USA (Cione et al. 2002) found that cutting invasive grasses followed by sowing of shrub seeds increased shrub seedling abundance and reduced grass cover. After one year, areas where grasses were cut and seeds were sown had more shrub seedlings (1-23 seedlings/m2) than areas that were not cut or sown with seeds (0 seedlings/m2). In areas where invasive grasses were cut and seeds were sown, grass cover was lower (13%) than in areas where invasive grasses were not cut or seeds sown (84%). In 1997–1998 grass was cut by hand in five randomly located 5 m x 5 m plots, after which seeds of native shrubs were sown, while in five other plots no grass was cut and seeds were not 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 exotic grass species in California, USA (Marushia & Allen 2011) found that sowing seeds of native species, followed by mowing, did not reduce the cover of non-native species nor did it increase the cover or number of native plant species. In areas that were seeded and mown cover of non-native plant species (43%) was not significantly different from areas that had been seeded but not mown (63%). Cover and number of native plant species were also not significantly different in areas that had been seeded and mown (cover: 18%; number of species: 5) compared to areas that had been seeded but not mown (cover: 24%; number of species: 4). In 2005 five 5 m2 plots were sown with seeds of shrubland species and mown, while five other plots were sown with seeds but not mown. Plant cover was measured in 0.5 m2 quadrats placed in each plot.
- Eliason S.A. & Allen E.B. (1997) Exotic Grass Competition in Suppressing Native Shrubland Re-establishment. Restoration Ecology, 5, 245-255
- 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