Role of phosphorus and soil biota in the restoration of species rich vegetation types via phosphorus-mining

The European Habitats Directive urges the European member states to take measures for maintaining and restoring natural habitats. In Flanders, the surface area of nature reserves is intended to be enlarged with at least 18.000 ha in order to halt the loss of biodiversity by 2020. Species rich grasslands are considered to be high priority habitat types that decreased dramatically in area due to agricultural intensification. Abandoned agricultural fields are the only main option to restore these habitat types, but success is poorly achieved due to two bottlenecks. The first is the immense accumulated phosphorus (P) pool fixated in the soil due to yearly fertilization in the agricultural context. High bio-available P concentrations homogenize vegetation due to the dominant growth by a few competitive species. The second bottleneck to success in restoration of species rich grasslands is the lack of typical soil biota essential for the establishment of target vegetation types. It remains unclear whether soil biota from target grasslands can survive and function at soils richer in bioavailable P. With this in mind, the conditions for restoring these vegetation types could be less strict than initially assumed. In a second part of this project, we focus on the development of an alternative restoration method. Traditionally, the soil P pool is depleted by cropping and removing the biomass, which is very time-consuming (several hundred years) because of a depression in grass-biomass after a few years. Another, more recent method is topsoil removal, where the P-saturated soil is taken away. This is a very expensive operation where also the soil buffering components and soil biota are exported. We aim to develop an alternative, the phytoextraction of P, also P-mining. This is the deprivation of soil P with a crop with high P-use efficiency and non-P fertilization. This method allows the gradual transition from agricultural land use towards nature management. Currently, there is a lack of insight in the time this restoration method will take because the bioavailable P-pool is continuously repleted by the slowly cycling P-pool.. Experiments with biological and chemical soil additions as well as crop rotations are conducted to propose an alternative for the current restoration methods.

Contact: Stephanie Schelfhout
Funding: University College Ghent (Onderzoeksfonds)
Supervisors: Prof. dr. ir. K. Verheyen, Prof. dr. ir. J. Mertens
Co-supervisors: dr. ir. A. De Schrijver, Prof. dr. ir. G Haesaert
Period: 2012-2018