Abstract
Wildflower strips have been heralded as a promising way to enhance ecosystem services by providing organisms which may help make farming less dependent on external inputs. However, recent studies show inconsistent effects on delivery of ecosystem services and crop yield, warranting a more detailed analysis of the factors determining the effects of wildflower strips. We examined how the natural enemy groups of spider, carabid beetle and staphylinid beetle, as well as aphid pest and crop yield respond to wildflower strips. We furthermore determined whether the response of natural enemies, aphids and crop yield depends on flower cover and species richness, and how this is influenced by fertilizer and insecticide applications to the crop in 16 winter wheat fields in the Netherlands. We used an experimental approach with a nested design that included all combinations of wildflower strips (present/absent), fertilizer application (yes/no) and insecticide application (yes/no). Presence of wildflower strips did not affect ground-dwelling natural enemies, aphids or crop yield. However, flower availability across wildflower strips and control margins was positively related to the abundance of the pooled number of examined natural enemies, spiders and carabid beetles. Positive effects in the crop were observed over limited distances; up to 5 m from the edge for spiders and wheat yield. The effects of flower availability and on-field management practices on natural enemies, aphids and wheat yield did not interact suggesting that, in our study, effects of flowers were not influenced by insecticide or fertilizer applications but were mainly additive. Our study indicates that cover and richness of wildflowers in field margin habitat, rather than establishment of wildflower strips per se, drove increases in natural enemies and crop yield. This suggests that more attention should be given to the optimization of establishment success of seed mixtures and management practices enhancing wildflower cover and diversity. Furthermore, biodiversity enhancing management of the herbaceous vegetation in linear landscape elements may represent a cost-effective alternative to boost ecosystem services regulating crop production in agricultural landscapes.
Highlights
Expansion and intensification of agriculture since the Green Revo lution in the 1960s have boosted agricultural production, but have had significant negative impacts on the environment (Matson et al, 1997)
Abundance of total natural en emies was best explained by a model including distance to field margins, flower cover and the interaction between the two factors
The fact that many of these strips comprised few wildflowers, sometimes even less than the pre-existing field boundary, is a meaningful and important result. It suggests that more attention should be given to environmental factors impacting the quality of wildflower strips, which management practices can be used to enhance floral resources and how this can be incorporated into agri-environmental scheme design and prescriptions (Cole et al, 2020)
Summary
Expansion and intensification of agriculture since the Green Revo lution in the 1960s have boosted agricultural production, but have had significant negative impacts on the environment (Matson et al, 1997). Delivery of pest control services in agricultural fields has been shown to depend on the composition of the surrounding landscape, with landscapes containing less semi-natural habitats providing less pest control services and lower crop yield (Dainese et al, 2019). This suggests that in simplified agricultural landscapes where few semi-natural habitats remain, creating new semi-natural habitats may be an effective way of enhancing natural pest control (Veres et al, 2013)
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