The relative effectiveness of different grassland restoration methods: A systematic literature search and meta-analysis

1. Active grassland restoration has gained in importance to mitigate the dramatic decline of farmland biodiversity. While there is evidence that such operations are generally effective in promoting plant diversity, little is known about the effectiveness of the different methods applied. Restoration methods can differ in intensity of seed bed preparation, seed source and technique of seed application.
2. In this systematic literature search and meta-analysis, we screened the literature for studies of the restoration of mesic grasslands in temperate Europe. We focused on active restoration experiments that included a treatment and lasted more than three years. We evaluated the influence of restoration factors on plant species richness relative to non-restored controls.
3. We found 187 articles that investigated the outcome of operations aimed at actively restoring mesic temperate grasslands. Most articles focused on plants, with only 9.6% dealing with other organisms (e.g. beetles, polli..., We followed the guidelines of the Collaboration for Environmental Evidence (Pullin & Stewart, 2006) and the ROSES standard (see ROSES form in Table S1) to conduct our systematic literature search. By doing so, we ensure repeatability of our search and screening process (Romanelli, Meli, Naves, Alves, & Rodrigues, 2021; Romanelli, Silva, et al., 2021). We prepared a protocol that was peer-reviewed and published (Slodowicz, Humbert, & Arlettaz, 2019). As some points of the original protocol had to be amended due to some unexpected issues, the following section contains the updated protocol.
Systematic literature search
We formulated our research question according to the PICO-structure (population, intervention, control, outcome): Do different seed addition methods for the restoration or re-creation of species-rich grasslands differ in their effectiveness to enhance the diversity of plants? (See Table S2 for details on the question components). Based on the question component..., All analyses were performed with R version 4.1.1 (R Core Team, 2021) using the metafor (Viechtbauer, 2010) and puinform packages (van Aert, 2018).