Enhancing floral resources for pollinators in productive agricultural grasslands

摘要

Across N.W. Europe intensive agricultural management has increased productivity to the detriment ofudfloral resources vital for insect pollinators like bees, butterflies and hoverflies. While the creation ofwild-udflower habitats has been widely used to re-establish such resources into arable ecosystems (e.g. sownudinto field margins), comparable low cost methods for enhancing floristic diversity in production grass-udlands are lacking. We investigated how simple and cheep seed mixtures based around three plant func-udtional groups (grasses, legumes and non-leguminous forbs) could be used to enhance flowering resourcesudto benefit insect pollinator communities over a four year period. Wedemonstrate that the abundance andudspecies richness of pollinators was correlated with the increased availability of legume and non-legumeudforb flowers. While the flowering resources provided by agricultural cultivars of legumes declined rapidlyudonce sown, the inclusion of a forb component within seed mixtures was effective in increasing the long-udterm persistence of these resources. As a result the abundance and species richness of insect pollinatorsudover the four years showed greater stability where forbs were also sown. Sward management also playeduda role in the persistence of floral resources, with grazing more likely to maintain legume cover than cut-udting. In conclusion, we demonstrate that low cost seed mixtures can be used to enhance floristic diversityudto benefit pollinators, although the continued value of these grasslands over time is dependent on com-udplementarity between sown legumes and forbs. As permanent grassland covers c. 40% of the UK theudenhancement of their floristic diversity has a huge potential to benefit insect pollinators. The type of landudsharing approaches suggested here maintain modest agricultural productivity and so may be the mostudlikely to achieve benefit to pollinators through wide-scale farmer uptake.