Action: Add topsoil (alongside planting/seeding)
- One randomized, replicated, paired, controlled study in the USA found that addition of topsoil alongside sowing of seed increased the biomass of grasses but reduced the biomass of forbs in comparison to addition of topsoil alone.
Adding topsoil from shrublands to degraded shrubland sites may help to increase the number of seeds in the soil, thereby increasing the probability of shrubland plants becoming established. The addition of topsoil may also help to increase soil fertility or reduce the effects of processes that dramatically alter soil structure, such as mining or quarrying. Combined with planting or seeding addition of topsoil may help to increase germination and survival of shrubland plants.
Supporting evidence from individual studies
A randomized, replicated, paired, controlled study in 1997–2000 in a former coal mine in Wyoming, USA (1) found that addition of topsoil alongside sowing of seed increased the biomass of grasses but reduced the biomass of forbs in comparison to addition of topsoil alone. Areas where topsoil was added and seed sown had higher grass biomass (51-93 g/m2) than areas where topsoil alone was added (14 g/m2). However, in areas where topsoil was added and seed sown, forb biomass was lower (12-37 g/m2) than in areas where topsoil was added alone (76 g/m2). Topsoil was spread to a depth of 56 cm over the entire site in December 1997. In spring 1998 the entire site was seeded with barley Hordeum vulgare which was later cut to provide a mulch. In December 1998 grass seed was sown in twenty 6.5 x 27 m plots, while in four plots no seed was sown. Wyoming big sagebrush Artemisia tridentata wyomingensis seeds were also sown in all plots. In July 2000 clippings of vegetation were taken in four 0.18 m2 quadrats within each plot to determine biomass.