Data from: Annual flower strips support pollinators and potentially enhance red clover seed yield

1. Ecological intensification provides opportunity to increase
agricultural productivity while minimizing negative environmental impacts,
by supporting ecosystem services such as crop pollination and biological
pest control. For this we need to develop targeted management solutions
that provide critical resources to service-providing organisms at the
right time and place. 2. We tested whether annual strips of early
flowering phacelia Phacelia tanacetifolia support pollinators and natural
enemies of seed weevils Protapion spp., by attracting and offering nectar
and pollen before the crop flowers. This was expected to increase yield of
red clover Trifolium pratense seed. 3. We monitored insect pollinators,
pests, natural enemies and seed yields in a total of 50 clover fields
along a landscape heterogeneity gradient, over two years and across two
regions in southern Sweden. About half of the fields were sown with flower
strips of 125 to 2000 m2. 4. The clover fields were pollinated by 60%
bumble bees Bombus spp. and 40% honey bees Apis mellifera. The clover seed
yield was negatively associated with weevil density, but was unrelated to
bee species richness and density. 5. Flower strips enhanced bumble bees
species richness in the clover fields, with the strongest influence in
heterogeneous landscapes. There were few detectable differences between
crop fields with and without flower strips. However, long tongued bumble
bees were redistributed towards field interiors and during phacelia bloom
honey bees towards field edges. Clover seed yield also increased with
increasing size of the flower strip. 6. Synthesis and application. Annual
flower strips of early flower resources can support bumble bee species
richness and, if sufficiently large, possibly also increase crop yields.
However, clover seed yield was mainly limited by weevil infestation, which
was not influenced by the annual flower strips. A future goal should be to
design targeted measures for pest control.