Action: Add mulch to control grass and sow seed
- One randomized, controlled study in the USA found that adding mulch, followed by seeding with shrub seeds, increased the seedling abundance of one of seven shrub species but did not reduce grass cover.
Mulch is usually an organic material such as leaves, grass cuttings, or wood chips that is applied to the top layer of soils. Using mulch directly on unwanted plants can reduce the amount of light they receive and therefore may reduce their abundance. Combining this with the addition of seeds of shrubland plants may aid on the establishment of shrubland species.
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 adding mulch, followed by seeding with shrub seeds, increased the seedling abundance of one of seven shrub species but did not reduce grass cover. After one year, areas where mulch and shrub seeds were added did not have a significantly higher number of shrub seedlings for two of seven species (1 seedlings/m2) than areas where mulch and seed were not added (0 seedlings/m2). There was also no significant difference in grass cover between areas where mulch and seeds had been added (76%) and areas where neither mulch, nor seeds were added (84%). In 1997 mulch was added to five randomly located 5 m x 5 m plots which were subsequently sown with seeds from native shrubs, while in five other plots no mulch or seeds were added. 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.