Extensively managed grasslands are nutrient-poor and therefore home to very diverse species communities. In Switzerland, however, fertilization and frequent mowing have transformed many former species-rich grasslands into highly productive, but species-poor, agricultural ‘deserts’. Nature conservationists want to restore them in, for example, protected areas. One controversial but efficient intervention for this purpose is topsoil removal, where some of the nutrient-rich topsoil layer is removed with a digger. Fresh hay and seeds from target plants are then added. Soil experts, however, have criticised this, maintaining it permanently disturbs the soil.
Carol Resch, an environmental scientist at WSL, was able to counter this objection with the help of nematodes, which are belowground indicators of soil conditions. Thus the more complex the network of herbivorous, bacterivorous, fungivorous, and omni-carnivorous nematodes, the healthier the soil is. Carol has studied eleven restored grasslands in the Eigental nature reserve (ZH), where 22 years ago nutrients were removed in various ways. She found that topsoil removal with and without seed addition was able to restore the targeted plant community, while repeated mowing alone was not enough. In addition, the soil nematodes successfully recovered from the digging. “Topsoil removal alone would be sufficient in the long term to restore species-rich grasslands,” Carol concludes. “But if this is to be achieved more quickly, seed will have to be added.” (Beate Kittl, Diagonal 2/19)