Grasslands are among the most threatened terrestrial biomes, and habitat conservation alone will be insufficient to meet biodiversity goals. While restoration of indigenous grasslands is a priority, conflict with economic objectives means that incorporation of alternative habitats is necessary to offset grassland loss. With up to 800,000 km2 of land affected by mining globally, there is an opportunity to create additional grassland habitat in post‐mining landscapes. We aimed to assess whether co‐introduction of native arbuscular mycorrhizal (AM) fungi and plants is an efficient means of initializing species‐rich vegetation recovery in barren post‐mining landscapes. We established an experiment in three post‐mining areas in Estonia, where we seeded plots with native plant seeds and inoculated them with trap‐cultured native AM fungi from a similar habitat. We measured the abundance and composition of soil AM fungal and above‐ground plant communities in two consecutive years using relevés, high‐throughput sequencing and fatty acid profiling. Our results demonstrate that co‐introduction of native plants and AM fungi is an effective way to establish species‐rich vegetation in post‐mining areas. Co‐introduction of symbiotic partners resulted in higher richness, diversity and abundance of plants and AM fungi than when either partner was introduced individually. However, the plant and AM fungal communities in sown and inoculated plots were not distinct from those in uninoculated treatments; they rather formed a subset of all taxa present on the sites but exhibited higher diversity than in uninoculated plots. Synthesis and applications. This study shows that managing the below‐ground microbiome is an essential part of vegetation restoration. The availability of symbiotic partners can be considered a key aspect determining the diversity of restored vegetation. Targeted inoculations with native and habitat‐specific native arbuscular mycorrhizal fungi could therefore increase restoration success.

1. During the past century, semi-natural grasslands, once widespread throughout Europe, have largely been converted into intensively managed agricultural areas, abandoned or afforested. These large-scale land-use changes have already resulted in considerable biodiversity loss but can also lead to decline in ecosystem service provision and ecosystem multifunctionality.2. We assessed the impact of afforestation and abandonment of semi-natural grasslands on the supply of ecosystem services in Western Estonia. We compared a wide array of services provided by open grasslands, abandoned grasslands and afforested grasslands. Additionally, we analysed the impact of land-use change and species richness on ecosystem multifunctionality.3. Significant declines in the supply of pollination services, natural pest regulation, forage production, soil quality, wild food and cultural appreciation of landscape were detected as a result of overgrowing or afforestation.4. There was significant positive relationship between species richness and ecosystem multifunctionality, that is, more biodiverse grasslands were able to support more services at higher capacity. 5. Results show that both grassland degradation due to abandonment, as well as grassland afforestation, have significant negative impacts on biodiversity, on the supply of multiple important ecosystem services and on the ecosystem multifunctionality.6. Synthesis and applications. Temperate semi-natural grasslands have high biodiversity and capacity to deliver multiple important ecosystem services simultaneously.

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