Moving to the real world: Testing biodiversity and priority effects for restoring multifunctional grasslands
The Otterzentrum Hankesbüttel carried out large scale riparian restoration of the Ise river in the early 1990s, financed by the Federal Ministry of Conservation (BfN), that included the purchase of many hectares of grassland and cropland in the river catchment. The riparian restoration was a success and many otters now thrive again in this region. The story for the grasslands is different.Some of the areas purchased were restored to grassland whereas other sites already were grasslands, creating an overall mosaic of 500 ha of grasslands that were sub-let to local farmers who manage the sites. These 500 ha of grassland, some meadows some pastures, have been managed mainly extensively since: many sites, however, regularly received 80kg N per ha per year since the 1990s. Despite the generally extensive management both pastures and meadows have not experience increases in plant diversity over time. The current project aims to study options for transforming this system to make it more biodiverse and to increase functioning and ecosystem services. We aim to do ground truthing of promising seeming concepts and knowledge from biodiversity and assembly research in ecology together wither the local farmers and the Otterzentrum. We will test whether sowing more diverse grassland mixtures of regional seeds compared to lower diversity mixtures and stopping or decreasing fertilization of specific fields, can improve restoration outcomes and lead to higher multifunctionality of the sites (including higher hay yield despite lack of fertilization). In a second approach we will test the potential for priority effects, caused by sowing different plant functional groups earlier than others (legumes, grasses, forbs), to enhance hay productivity while also improving plant community diversity. These experiments will be set up on 10-14 different fields that differ in their connectivity to one another and their land use history (some were restored in the 1990s, others have been grassland for a much longer time). In this study each treatment sowing site is scaled up to an extend of 30 x 30 meters to test for „real-world“ grassland restoration effects. Based on the 25-year old large-scale Ise restoration project we assess the impact of management practice (different levels of fertiliser input), habitat characteristic (converted vs. continuous grassland) and landscape connectivity (connected vs. isolated grassland fields) using plant and butterfly assemblies and biomass productivity as proxies for biodiversity and ecosystem service, respectively.