Restoration groundwork: testing large-scale soil transplantation to facilitate rapid vegetation development on former arable fields

The restoration of former arable fields to semi-natural grasslands is an important method for counteracting the loss of species rich grasslands in northwestern Europe. Restoration of these areas is a long process that may take decades or even centuries. High nutrient availability as well as lack of an appropriate seedbank are well-known bottlenecks for restoration. However, recent fundamental research into plant-soil interactions has demonstrated that the soil community also plays a crucial role in driving the secondary succession on ex-arable fields. Yet an explicit belowground perspective in nature restoration has so far not been applied in practice. Here we report on the first field experiment transplanting soil communities from well-developed nature areas to a new restoration area performed at a spatial scale relevant for restoration practice. In 2006, transplantation of both soil from a species-rich grassland and sods from a heathland were carried out in four replicate areas (2.5-5 ha) at the Reijerscamp (the Netherlands), a 160 hectare ex-arable field. To compare with conventional restoration measures hay was spread over similar areas and these treatments were executed both on the original soil as well as on areas where the top-soil had been removed. After six years the restoration success was evaluated by quantifying vegetation structure and composition in 1x1m plots. Furthermore, fungal (PLFA, T-RFLP), bacterial (PLFA), nematode and microarthropod abundance and composition, as well as soil acidity, organic matter and nutrient content were measured in each plot. Preliminary analyses show that the transplantations and particularly the addition of sods has increased plant cover in top-soil removal areas and promoted plant diversity in general. This suggests that soil transplantation may be an effective measure to jump-start the restoration of species-rich vegetation on former arable fields.