| 1. |
- Bommarco, Riccardo, et al.
(författare)
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Flower strips enhance abundance of bumble bee queens and males in landscapes with few honey bee hives
- 2021
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Ingår i: Biological Conservation. - : Elsevier BV. - 0006-3207 .- 1873-2917. ; 263
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Tidskriftsartikel (refereegranskat)abstract
- Wild bee declines in agricultural landscapes have led farmers to supplement crops with honey bees. Simultaneously, environmental subsidy and conservation programmes have incentivized farmers to establish flower strips to support wild and managed pollinators. To find out if flower strips enhance, and competition from honey bees suppresses, wild bees in the landscape and across seasons, we surveyed bumble bee and honey bee abundances in 16 sites in Sweden in summer 2018. The centre of each site (2 km radius) was with or without an annual flower strip, and with or without added honey bee hives. We surveyed bees in each flower strip and in linear habitats in the landscape around each site, such as field edges and road verges. In the following spring, we surveyed bumble bee queen abundance in each site. We show that adding flower strips benefits bumble bee queen abundance the following year, but this effect is diminished if honeybee hives are added. In sites with flower strips, added honey bee hives reduced male bumble bee abundance. Our relatively small flower strip areas bolstered bumble bee population growth across seasons, probably by relieving a resource bottleneck. Adding honey bee hives in combination with flower strips to landscapes with few floral resources should be avoided as it cancelled the positive effect of flower strips.
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| 2. |
- Lundin, Ola, et al.
(författare)
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Landscape complexity benefits bumble bee visitation in faba bean (Vicia faba minor L.) but crop productivity is not pollinator-dependent
- 2021
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Ingår i: Agriculture, Ecosystems and Environment. - : Elsevier BV. - 0167-8809 .- 1873-2305. ; 314
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Tidskriftsartikel (refereegranskat)abstract
- Faba bean (Vicia faba minor L.) is partially dependent on insects for pollination, but the degree of pollinatordependency and whether crop productivity is limited by insufficient insect pollination remain unknown. We monitored insect pollinators and their foraging behaviors (i. e., legitimate flower visitation, nectar robbing and extra-floral nectary visitation) in a total of 20 faba bean fields of a single cultivar (Tiffany) 2018?2019. Focal fields were situated along a gradient of landscape complexity. In each field, a pollination experiment was established, where plants were either bagged to exclude pollination by insects or remained open for pollinator visits. In addition, all flowers on half of the bagged and open-pollinated plants were pollinated by hand to measure the degree of pollen limitation. We found that bumble bee abundance was higher, and legitimate flower visitor abundance tended to be higher, in complex landscapes with more semi-natural habitat, indicating that the faba bean pollination potential is higher in complex landscapes. The pollination experiment showed that the number of beans per pod was lower in bagged plants compared with other treatments in one of the years, but the lower number of beans per pod was compensated for by a higher individual bean weight, such that there was no pollinator-dependency or effect of hand pollination on total bean mass per plant. We conclude that to be able to characterize the value of insect pollination services in faba bean we need an improved understanding of how pollinator-dependency varies across modern cultivars, and how environmental conditions can increase or, as in our case, cancel this pollinator-dependency.
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| 3. |
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| 4. |
- Raderschall, Chloë, et al.
(författare)
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Annual flower strips and honeybee hive supplementation differently affect arthropod guilds and ecosystem services in a mass-flowering crop
- 2022
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Ingår i: Agriculture, Ecosystems and Environment. - : Elsevier BV. - 0167-8809 .- 1873-2305. ; 326
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Tidskriftsartikel (refereegranskat)abstract
- Intensively managed agricultural landscapes have degraded the provisioning of diverse and continuous forage and shelter habitats for arthropods and weakened the delivery of ecosystem services such as insect crop pollination and biological pest control. In response, farmers are incentivised to sow flower strips along field margins to counteract resource bottlenecks. Yet, it is poorly understood how effective this diversification practice is when combined with the supplementation of honeybee (Apis mellifera L.) hives, which is commonly used to boost insect pollination in flowering crops. Honeybees share floral resources with wild pollinators and natural enemies of pests, which could lead to competition for food resources. We sampled pollinators, natural enemies and their pests as well as estimated the benefit of insect pollination in 17 organic faba bean (Vicia faba minor L.) fields in southern Sweden either with or without sown annual flower strips and with or without added honeybee hives. In fields with flower strips, bumblebee (Bombus spp.) densities were redistributed from field edges to interiors but without affecting their overall densities. Flower strips enhanced silver Y moth (Autographa gamma L.) densities and carabid beetle Shannon diversity along the field edge, and overall spider activity density. The supplementation of honeybee hives enhanced honeybee densities, overall ladybird beetle densities, black bean aphid (Aphis fabae Scop.) densities along field edges, but deterred silver Y moths and pushed bumblebees towards the field interior. Bean mass per plant was higher in insect pollinated plants compared with bagged, self-pollinated plants. This insect pollination benefit was independent of honeybee hive supplementation and the flower strip treatment suggesting that faba bean fields were not deficient in pollinator visits. We conclude that flower strips did not provide sufficient floral resources to increase overall wild pollinator densities in faba bean fields. Yet, annual flower strips attracted and facilitated ground-dwelling predators, especially spiders, to faba bean fields, likely by providing beneficial shelter habitats. It is worth noting that 2018, in which we collected our data, was characterised by late frosts in spring followed by an unusually hot and dry summer. While these unforeseen weather conditions together with a relatively small sample size might limit the generalisation of our results, we argue that conducting experiments under such conditions provide insights into the effectiveness of agri-environmental schemes under climate change, especially considering that such weather conditions are becoming increasingly more frequent.
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| 5. |
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| 6. |
- Raderschall, Chloë
(författare)
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Crop and landscape heterogeneity increase biodiversity in agricultural landscapes: A global review and meta-analysis
- 2024
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Ingår i: Ecology Letters. - 1461-023X .- 1461-0248. ; 27
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Forskningsöversikt (refereegranskat)abstract
- Agricultural intensification not only increases food production but also drives widespread biodiversity decline. Increasing landscape heterogeneity has been suggested to increase biodiversity across habitats, while increasing crop heterogeneity may support biodiversity within agroecosystems. These spatial heterogeneity effects can be partitioned into compositional (land-cover type diversity) and configurational heterogeneity (land-cover type arrangement), measured either for the crop mosaic or across the landscape for both crops and semi-natural habitats. However, studies have reported mixed responses of biodiversity to increases in these heterogeneity components across taxa and contexts. Our meta-analysis covering 6397 fields across 122 studies conducted in Asia, Europe, North and South America reveals consistently positive effects of crop and landscape heterogeneity, as well as compositional and configurational heterogeneity for plant, invertebrate, vertebrate, pollinator and predator biodiversity. Vertebrates and plants benefit more from landscape heterogeneity, while invertebrates derive similar benefits from both crop and landscape heterogeneity. Pollinators benefit more from configurational heterogeneity, but predators favour compositional heterogeneity. These positive effects are consistent for invertebrates and vertebrates in both tropical/subtropical and temperate agroecosystems, and in annual and perennial cropping systems, and at small to large spatial scales. Our results suggest that promoting increased landscape heterogeneity by diversifying crops and semi-natural habitats, as suggested in the current UN Decade on Ecosystem Restoration, is key for restoring biodiversity in agricultural landscapes.We demonstrate overall positive effects of crop and landscape compositional and configurational heterogeneity on alpha-level biodiversity (total abundance, species richness or Shannon diversity) for plants, invertebrates, vertebrates, pollinators and predators on a global scale. We also show that the positive effects of these heterogeneity components are consistent for invertebrates and vertebrates in both tropical/subtropical and temperate agroecosystems, and in annual and perennial cropping systems and at small to large spatial scales. These results suggest that small structural adjustments in compositional and configurational heterogeneity compatible with commercial farming systems (averaging 75% cropped area) can provide significant benefits for native biodiversity.image
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| 7. |
- Raderschall, Chloë
(författare)
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Diversified agroecosystems for biodiversity and ecosystem services : Ecological intensification of faba bean cropping under land use and climate change
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Loss of natural habitats and lack of continuous floral resources in intensive agricultural landscapes limit the population growth of ecosystem service providers, such as pollinators. Weakened ecosystem service delivery and climate change stressors contribute to crop yield instability. The aim of my thesis was to explore how resource diversification strategies at both field and landscape scale influence arthropod communities and the services they provide, such as pollination and biological pest control. Further, I explored how climate change stressors such as water stress and insect herbivory interact with insect pollination and affect crop yield. To address these aims, I used faba bean cropping as a model system. I found that landscape crop diversity enhanced bumble bee densities and flower strips enhanced ground predators in the crop. Flower strips boosted and honey bee hives counteracted bumble bee queen abundances in the landscape across seasons. Using pollinator exclusion experiments, I showed that insect pollination increased yield. This insect pollination benefit decreased with increasing semi-natural habitat cover in the landscape but was constant irrespective of plant water stress and insect herbivory. I demonstrated that the highest yields are achieved when water stress and insect herbivory are reduced simultaneously. My thesis emphasises that diversified agroecosystems are particularly important in the face of climate change, because they 1) enhance ground predators that can safeguard crops from herbivore outbreaks, and 2) provide pollinators with floral resource continuity, which arguably is particularly important during extremely hot and dry summers, where landscape-wide floral resource bottlenecks are worsened by shortened bloom periods.
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| 8. |
- Raderschall, Chloë, et al.
(författare)
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Insect pollination enhances faba bean yield more than weed removal or fungicide application
- 2024
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Ingår i: Agriculture, Ecosystems and Environment. - 0167-8809 .- 1873-2305. ; 374
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Tidskriftsartikel (refereegranskat)abstract
- Insect pollinators provide important crop pollination services but are declining in response to lack of diverse flower resources and exposure to pesticides. Despite increasing evidence that the benefits of insect pollination for crop production depend on other ecosystem services and crop management practices, investigations have mostly been limited to how pollination benefits are affected by insect pest control and soil fertility levels. Here we used a factorial cage experiment in the field to test how pollination by bumble bees, manual weed removal and fungicide application interactively shape faba bean (Vicia faba) yield components, and how weed removal and fungicide application affect bumble bee foraging behaviour. We found that insect pollination and weed removal increased faba bean yield components mostly additively, with insect pollination being the most important factor to maximise yield. The fungicide treatment did not affect crop yield, probably due to the low fungal pathogen incidence in the experiment, but instead affected bumble bee visitation behaviour. Bumble bees visited flowers of fungicide-sprayed plants more often than fungicide-free plants. This has potential consequences on bee health that should be further assessed. Guidelines on pesticide use should be improved by weighing benefits to agricultural productivity against risks for pollinators according to integrated pest and pollinator management principles. Our results emphasise that insect pollination can be an important factor for crop yield. The additive benefits of insect pollination and weed removal to crop yield indicates that they are crop production factors which can be managed for independently.
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| 9. |
- Raderschall, Chloë, et al.
(författare)
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Landscape crop diversity and semi-natural habitat affect crop pollinators, pollination benefit and yield
- 2021
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Ingår i: Agriculture, Ecosystems and Environment. - : Elsevier BV. - 0167-8809 .- 1873-2305. ; 306
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Tidskriftsartikel (refereegranskat)abstract
- Agricultural intensification has led to the conversion of natural habitats into agricultural fields, increased field sizes and simplified crop rotations. The resulting homogenisation of the landscape has led to a decline in bees, which provide an essential ecosystem service to agriculture. It has been suggested that an increase in landscape crop diversity supports higher biodiversity by providing more diverse and continuous resources without taking land out of agricultural production. We selected 14 faba bean (Vicia faba minor L.) fields in southern Sweden along uncorrelated gradients of landscape crop diversity and proportion of semi-natural habitat within 1.5 km radii surrounding focal fields. Pollinator surveys and pollinator exclusion experiments were conducted to assess whether landscape crop diversity affected pollinator densities, pollinator foraging behaviour (i.e. legitimate flower visitation, nectar robbing or extra-floral nectary visitation), pollination and yield formation. Landscape crop diversity enhanced bumble bee densities. Insect-pollinated faba bean plants produced, on average, 27 % higher bean weight per plant than bagged plants and the insect pollination benefit decreased with increasing semi-natural habitat cover. Bumble bee and honey bee densities, the proportion of nectar robbing bees as well as faba bean yield increased with increasing proportion of semi-natural habitat. Pollinator densities were not the driver of high yields associated with higher proportions of semi-natural habitat because the observed yield increase was unrelated to pollinator densities and driven by bagged plants that were excluded from pollinator visits. Insect pollination, however, clearly decreased the yield gap associated with low proportions of semi natural habitat in the landscape. Our results highlight that agri-environmental policies should promote the retention of existing semi-natural habitats and encourage landscape crop diversity to provide pollinators with sufficient food and nesting resources.
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| 10. |
- Raderschall, Chloë, et al.
(författare)
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Legacy of landscape crop diversity enhances carabid beetle species richness and promotes granivores
- 2022
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Ingår i: Agriculture, Ecosystems and Environment. - : Elsevier BV. - 0167-8809 .- 1873-2305. ; 340
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Tidskriftsartikel (refereegranskat)abstract
- It is well understood that agricultural expansion and associated loss of semi-natural habitat in the landscape are major drivers for the marked decline in biodiversity. While conserving remaining semi-natural habitat patches is essential to reverse ongoing biodiversity declines, increasing focus has also been put on diversifying cropland itself by increasing landscape crop diversity as a measure of compositional heterogeneity, and reducing field sizes as a measure of configurational heterogeneity. Both these cropland diversification approaches have shown promise to enhance biodiversity in the year of sampling, but it is unknown whether legacies of crop diversity in the landscape promote biodiversity by building up arthropod communities over time. We selected 14 faba bean fields in landscapes dominated by cropland. The fields were chosen along three gradients: landscape crop di-versity of the year of sampling (2017), landscape crop diversity of the previous year (2016) and mean field size in landscapes. Using pitfall traps, we show that the carabid beetle species richness is higher in landscapes with higher crop diversity in the previous year. Especially, granivorous carabid beetles benefitted from legacies of crop diversity. Rove beetles were more abundant and genus rich in landscapes with larger field sizes, while spiders were not responding to any of the landscape variables. A diversity of crops in the landscape and their associated weed communities could provide more diverse food resources and shelter habitats, which build populations of carabid beetle species over time. There is a need to explore the effects of agri-environmental schemes across multiple years to better understand legacy effects, and to structure sustainable agricultural landscapes.
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