title: Grassland Restoration: Relative effectiveness of different restoration methods on plant and invertebrate diversity
Creators: name: Slodowicz, Daniel
Publisher: name: Universität Bern
Year: 2023
Subjects: subject: 570 Life sciences; biology
subject: 590 Animals (Zoology)

description: Semi-natural grasslands in Central Europe can harbor a big variety of plant and invertebrate species. These grasslands have suffered from a strong decline mainly due to agricultural intensification. Agri-environment schemes have been introduced in Europe to promote farmland biodiversity, but they were only little effective, especially so in grasslands. To mitigate this dramatic decline of farmland biodiversity, active grassland restoration is nowadays widely applied and has gained in importance in research. While there is evidence that active grassland restoration is generally effective in promoting plant diversity, little is known about the effectiveness of the factors involved in such restoration operations, such as soil disturbance intensity, seeding methods and seed source. Furthermore, there are no studies showing whether the soil disturbances that are linked to grassland restoration could be harmful to the resident ground-dwelling invertebrates of a grassland that is going to be restored.
In this PhD thesis I investigated the effects of different factors involved in active grassland restoration on the restoration outcome. I first conducted a systematic review and meta-analysis to evaluate the relative influence of these factors on restoration efficacy, focusing on plant species richness, and to identify research gaps. In parallel, a field-scale restoration experiment replicated across the Swiss Plateau was launched, with this PhD being part of the restoration experiment. This experiment served to study whether hay transfer can be used to effectively transfer invertebrates from one meadow to another and to which degree soil disturbances linked to grassland restoration are harmful to ground-dwelling invertebrates. Furthermore, I studied the short-term outcome of different restoration methods on the plant community. The restoration methods were: (i) control with no seed addition and no soil disturbance, (ii) hay transfer from a species-rich donor meadow on a harrowed receiver meadow, (iii) hay transfer from a species-rich donor meadow on a ploughed receiver meadow, (iv) sowing of a commercial seed mixture on a ploughed receiver meadow and, (v) sowing of a brush- or vacuum harvested seed mixture on a ploughed receiver meadow. Baseline data of plants and ground-dwelling invertebrates (represented by ground beetles and spiders) was collected in 2018, i.e., one year before restoration took place. In early summer 2019 we restored 48 meadows and additionally sampled invertebrates from the hay transfer treatments. One year after restoration (in 2020) we resampled invertebrates and two years after restoration (in 2021) we reconducted vegetation surveys on the restored and control meadows. 
The systematic review and meta-analysis revealed the importance of the seed source in grassland restoration, while different soil disturbance intensities or seeding methods (green hay or harvested seeds) do not show differences in the restoration performance on plant species richness. We also identified research gaps, such as little focus on invertebrates in grassland restoration studies and few field scale experiments. With the restoration experiments we could show that invertebrates can be transferred successfully with the hay and that there was no mid-term negative impact on the ground-dwelling invertebrate community due to soil disturbances linked to restoration, no matter of the disturbance intensity. Finally, all four restoration methods that we tested in our experiment significantly increased the plant species richness after two years. All together the present thesis is a contribution to the relatively young research field of restoration ecology with evidence-based recommendations and it comes in a timely moment within the UN decade on restoration.