Enhancing floral resources for pollinators in productive agricultural grasslands

Abstract

Contact CEH NORA team at noraceh@ceh.ac.ukThe NERC and CEH trademarks and logos ('the Trademarks') are registered trademarks of NERC in the UK and other countries, and may not be used without the prior written consent of the Trademark owner. hoverflies. While the creation of wildflower habitats has been widely used to re-establish such resources into arable ecosystems (e.g. sown into field margins), comparable low cost methods for enhancing floristic diversity in production grasslands are lacking. We investigated how simple and cheep seed mixtures based around three plant functional groups (grasses, legumes and non-leguminous forbs) could be used to enhance flowering resources to benefit insect pollinator communities over a four year period. We demonstrate that the abundance and species richness of pollinators was correlated with the increased availability of legume and non-legume forb flowers. While the flowering resources provided by agricultural cultivars of legumes declined rapidly once sown, the inclusion of a forb component within seed mixtures was effective in increasing the long-term persistence of these resources. As a result the abundance and species richness of insect pollinators over the four years showed greater stability where forbs were also sown. Sward management also played a role in the persistence of floral resources, with grazing more likely to maintain legume cover than cutting.In conclusion, we demonstrate that low cost seed mixtures can be used to enhance floristic diversity to benefit pollinators, although the continued value of these grasslands over time is dependent on complementarity between sown legumes and forbs. As permanent grassland covers c. 40 % of the UK the enhancement of their floristic diversity has a huge potential to benefit insect pollinators. The type of land sharing approaches suggested here maintain modest agricultural productivity and so may be the most likely to achieve benefit to pollinators through wide-scale farmer uptake.3

Ecological intensification to mitigate impacts of conventional intensive land use on pollinators and pollination

“…Improved grasslands can be managed for floral richness, by reducing fertiliser inputs or delaying mowing dates, which concomitantly increases the bee, hoverfly and/or butterfly diversity (Humbert et al 2012;van Swaay et al 2012;Dicks et al 2014aDicks et al , 2014b. Adding legumes and other flowering species to grassland seed mixtures supported by some agri-environmental schemes in Europe can probably further benefit pollinators (Dicks et al 2010Dicks et al 2014aDicks et al , 2014bWoodcock et al 2014).…”

Grassland Management Affects Delivery of Regulating and Supporting Ecosystem Services

“…Grasslands with greater plant species richness and more flower-rich species (e.g., forage legumes and forbs) provide greater foraging opportunities for pollinators (Potts et al, 2009;Hudewenz et al, 2012;Woodcock et al, 2014). This ES is vital to reduce pressure on the bee population.…”

“…Because grazing pressure affects grassland botanical composition, management should optimize spatial and temporal frequency of flowering plants that are beneficial for both cattle and pollinators. Reduced harvesting frequency and fertilization of forage plots benefited pollinators relative to greater management intensity (Hudewenz et al, 2012), and negative effects of intensive management were related to their effect on number of flowers (Woodcock et al, 2014). Delayed grazing to increase the presence of flowers increased pollinator abundance (Sjödin, 2007).…”

“…Grazing management and grassland structure and function are important. Grasslands with greater plant species richness and more flower-rich species (e.g., forage legumes and forbs) provide greater foraging opportunities for pollinators (Potts et al, 2009;Hudewenz et al, 2012;Woodcock et al, 2014). Frequency of pollinator visits increased linearly with increasing blossom cover and the number of flowering plant species (Ebeling et al, 2008).…”

Multi-scale effects of agri-environment schemes on carabid beetles in intensive farmland

“…In addition, an increase in beetle abundance or species richness may improve ecosystem resilience (Hooper et al, 2005). Crop pest consumption by carabids was found to be positively correlated to prey abundance (Menalled et al, 1999), while species richness may improve community functional resilience as well as biodiversity conservation (Tilman, 1996;Woodcock et al, 2014). Agricultural practices such as tillage or pesticide use have been shown to affect carabid abundance either directly, through mortality and emigration, or indirectly, by changing local microhabitat conditions (Cole et al, 2002;Hatten et al, 2007;Kromp, 1999).…”