Small biotopes: Landscape and management effects on pollinators

Sammanfattning: The intensification of agriculture during the second half of the twentieth century, has caused sever declines of farmland biodiversity, where loss of semi-natural habitats is one of the major drivers. To halt further loss of habitat and biodiversity, agri-environmental schemes (AES) are used to compensate farmers to use methods less harmful to the environment. In this thesis, I have investigated the importance of preserving small biotopes (e.g. field boundaries, road verges, field islets and marl pits) for the persistence of plants and pollinators in agricultural landscapes of varying complexity. I also evaluated the effectiveness of a Swedish AES focused on preventing woody encroachment of small biotopes, with the partial aim of benefiting biodiversity, on the species richness and abundances of pollinators. I surveyed plants and pollinators in different types of habitats found within agricultural landscapes, to investigate the relative importance of small biotopes as habitat for these two groups. I also investigated the local- and landscape-scale effects of removing woody vegetation from small biotopes on pollinators and pollination. The results showed that small biotopes are important for the preservation of both plants and pollinators, within agricultural landscapes of varying structural complexity. Their importance as habitat for pollinators is highest when no mass-flowering crops are available. I also show that the removal of woody vegetation from small biotopes can benefit some pollinator groups while others may be negatively impacted, and although management may benefit pollinators locally, it may not affect the occurrences of pollinators at larger spatial scales. However, the results show that benefits from management of small biotopes are likely to be higher within structurally simple landscapes. The results from this thesis, thus highlights the importance of preserving small biotopes within agricultural landscapes for the conservation of farmland biodiversity. They further illustrate the importance of evaluating and understanding the effects of agri-environmental schemes, since the efficiency of these to enhance biodiversity can vary between organism groups and depend on landscape structure.