Action: Add mulch to control grass
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- One randomized, controlled study in the USA found that areas where mulch was used to control grass cover had a similar number of shrub seedlings to areas where mulch was not applied. The same study found that mulch application 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.
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 did not increase the seedling abundance of shrub species or reduce grass cover. After one year, the number of seedlings for seven of seven shrub species did not differ between areas where mulch had been added (0 seedlings/m2) and areas without mulch (0 seedlings/m2). There was also no significant difference in grass cover between areas where mulch had been added (85%) and areas where mulch was not added (84%). In 1997 seeds were sown in five randomly located 5 m x 5 m plots, while in five other plots 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.