Re-establishing of grasslands

Agro-policy largely controls habitat amount, quality and composition of a landscape and thus affects species diversity and ecosystem services. Since 2008, EU subsidies for the establishment and maintenance of set-aside grassland fallows have been abolished, therefore this type of habitat currently disappears rapidly from European agroecosystems. Thus, the current removal of set-aside fallows will reduce biodiversity and key ecosystem services like pollination and biological pest control in European agroecosystems. In the proposed project we attempt to counteract this by re-establishing small grasslands to promote farmland biodiversity and key ecosystem services. In a three-year investigation the proposed project will investigate whether the re- establishment of small grasslands in the surroundings of a large semi-natural habitat remnant is a viable strategy to re-populate the landscape with beneficial species (epigeic predators: carabid beetles, spiders; pollinators: wild bees, hoverflies) and to increase ecosystem service efficacy of biological control and pollination, therewith transferring the positive effects of a habitat remnant into the open agricultural landscape. We will newly establish grasslands of 450 x 10 m as habitat and dispersal corridor for beneficial arthropods. Therefore, 72 study sites will be set up in an intensively managed agricultural region along transects from a semi-natural habitat remnant into adjacent arable land. Study sites are located within the habitat remnant, the newly established grasslands, in crop areas 20 m and 300 m from the grasslands. Epigeic predators are caught by pitfall traps, and pollinators are recorded by observations and sweep netting. Biological control efficacy of epigeic arthropods is measured by the predation rate on live dipteran larvae, and pollination success is measured on two species of self-incompatible, insect pollinated test plants. We will set up a randomized complete block design with repeated measurements over time to answer the following questions: 1) Are newly established grasslands appropriate to increase species richness and abundance of common agrobiont predators and pollinators within and nearby the grasslands in a short term? How do species specific traits affect temporal and spatial colonisation patterns of common agrobiont predators and pollinators? 2) Do newly established grasslands serve as temporal feeding habitats and dispersal corridor for habitat specialists dispersing from a semi-natural source habitat into the agricultural matrix, therewith expanding their operating range? How do species specific traits affect temporal and spatial colonisation patterns of habitat specialists? 3) Do newly established grasslands significantly enhance ecosystem service efficacy of biological control and pollination in the ambient agricultural land in a short term? 4) How are biological control and pollination related to species richness and abundance of epigeic predators and pollinators? The outcomes of the study may be fundamental for the development of agri-environment schemes that aim to conserve, enhance or re-establish key ecosystem services in European agricultural landscapes.

This project (2017-2019) investigated the contribution of newly established semi-natural habitats to the promotion of beneficial insect biodiversity and ecosystem services in the agricultural landscape. Flower-rich meadows (in the form of 10 m wide grassland strips) were established within agriculturally cultivated fields. The project phase covers the early colonization phase of newly established meadows by insects and spiders. Biodiversity and abundance of spiders, ground beetles, and ants, which make important contributions to pest reduction, as well as important pollinators such as wild bees, honey bees, bumblebees, and hoverflies were studied. In addition, studies were conducted on butterflies, grasshoppers, cicadas, and bugs, and experiments were conducted on the effectiveness of the ecosystem services biological pest control and pollination. Development of plant emergence was monitored, too. Animals, plants, and ecosystem services were studied in the newly established meadows, old meadows, and adjacent winter cereals. In addition, animal numbers were compared between new and old meadows and so-called biodiversity areas (subsidized ÖPUL areas). The uniqueness of the REGRASS project lies in the parallel, controlled experimental investigation of many organism groups and ecosystem services. The results of the project provide information on the initial colonization rate and thus on the effectiveness of newly established meadows as ecological compensation areas. With a regionally adapted seed mixture, species-rich, extensive meadow strips were established on all study areas. Pollinating insects reached very high individual and species numbers in newly established meadows. Compared to pollinators, colonization by predatory insects was much slower. Although species and individual numbers increased rapidly in these groups as well, even after three years the species community of spiders, ground beetles, and ants is still essentially that of a field. However, the spiders showed a marked change in distribution within the three years. While the species communities of the new meadows were very similar to those in the cereal in the first year, they evolved away from the cereal toward the old meadows in years 2 and 3, suggesting an incipient species exchange between old and new meadows. Based on very high numbers of individuals in the newly established meadows, spiders also showed significantly higher densities in cereal patches close to the new meadows than in cereal patches far from the new meadows, indicating an exchange between new meadows and adjacent cereals. Feeding on experimentally offered flies (as a measure of biological pest control) and pollination performance did not differ between meadows and cereals. However, there was a positive relationship between seed weight of test plants and number of pollinators, species number of pollinators, species number of plants, number of flowers, and vegetation cover. With the exception of species number pollinators and flower number, this was also true for seed number of test plants.