Traditional semi-natural grassland management with heterogeneous mowing times enhances flower resources for pollinators in farmed landscapes.

Abstract

Semi-natural grasslands are essential habitats for pollinators. They provide high diversity of floral resources, but the amount of floral resources is strongly affected by the timing of mowing. For pollinator species that are active throughout the season, it is important that pollen and nectar are available over the entire summer at spatially relevant scales [1]. A key task for semi-natural grassland conservation is to understand the link between timing of mowing and the phenology of the plant species providing floral resources. Environmental schemes normally include recommendations for when to mow, but these are often simplifications of the traditional practices, which shaped the species rich meadows. Several of these schemes focus on one late cut [2]. In this project we investigated the linkage between flower resources for pollinators and traditional mowing practices of hay meadows. The study was performed in an agricultural landscape with a high cover of small parcels of semi-natural hay meadows in the village Botiza in Maramures, Romania where species richness of plants in the meadows is extremely high. By studying this low-intensity farmland we generated knowledge about management methods that can be used in other parts of Europe where such landscapes are lost. We botanically surveyed 37 meadows that were cut early, intermediate, or late in the season. The surveys were performed in the beginning of August, a couple of weeks before the late cut. We recorded all herb and scrub species, phenological stages and the number of reproductive units per species. These were used as indicators for flower resources for pollinators. Data were analysed in DCA and GLM. The species richness was not affected by the mowing time but the speceis composition of species flowering at late mown hay meadows were diferent compared to in the hay meadows mowed early or intermediately. The proportion of species flowering and flower density were highest in the early mown meadows. Estimations based on phenological stages showed that late mown meadows are the main pollen source in July, whereas meadows mown early are the main source in the end of the season. The results demonstrate that heterogeneous mowing times yields floral resources for pollinators throughout the summer season. Various mowing times at a scale relevant for pollinators therefore need to be considered in pollinator conservation in agro-ecosystems. This study (project no 230278) was funded by The Research Council of Norway and the Swedish Biodiversity Centre, (Swedish University of Agricultural Sciences) and the museum of the Romanian Peasant.

1. Kovács-Hostyánszki, A., et al., Conservation of Pollinators in Traditional Agricultural Landscapes-New Challenges in Transylvania (Romania) Posed by EU Accession and Recommendations for Future Research. PloS one, 2016. 11(6)

2. Wehn, S., et al., Adaptive biodiversity management of semi-natural hay meadows: The case of West-Norway. Land Use Policy, 2018. 72