| 1. |
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| 2. |
- Garibaldi, Lucas A., et al.
(författare)
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Trait matching of flower visitors and crops predicts fruit set better than trait diversity
- 2015
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Ingår i: Journal of Applied Ecology. - : Wiley. - 1365-2664 .- 0021-8901. ; 52:6, s. 1436-1444
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Forskningsöversikt (refereegranskat)abstract
- Understanding the relationships between trait diversity, species diversity and ecosystem functioning is essential for sustainable management. For functions comprising two trophic levels, trait matching between interacting partners should also drive functioning. However, the predictive ability of trait diversity and matching is unclear for most functions, particularly for crop pollination, where interacting partners did not necessarily co-evolve. World-wide, we collected data on traits of flower visitors and crops, visitation rates to crop flowers per insect species and fruit set in 469 fields of 33 crop systems. Through hierarchical mixed-effects models, we tested whether flower visitor trait diversity and/or trait matching between flower visitors and crops improve the prediction of crop fruit set (functioning) beyond flower visitor species diversity and abundance. Flower visitor trait diversity was positively related to fruit set, but surprisingly did not explain more variation than flower visitor species diversity. The best prediction of fruit set was obtained by matching traits of flower visitors (body size and mouthpart length) and crops (nectar accessibility of flowers) in addition to flower visitor abundance, species richness and species evenness. Fruit set increased with species richness, and more so in assemblages with high evenness, indicating that additional species of flower visitors contribute more to crop pollination when species abundances are similar.Synthesis and applications. Despite contrasting floral traits for crops world-wide, only the abundance of a few pollinator species is commonly managed for greater yield. Our results suggest that the identification and enhancement of pollinator species with traits matching those of the focal crop, as well as the enhancement of pollinator richness and evenness, will increase crop yield beyond current practices. Furthermore, we show that field practitioners can predict and manage agroecosystems for pollination services based on knowledge of just a few traits that are known for a wide range of flower visitor species. Despite contrasting floral traits for crops world-wide, only the abundance of a few pollinator species is commonly managed for greater yield. Our results suggest that the identification and enhancement of pollinator species with traits matching those of the focal crop, as well as the enhancement of pollinator richness and evenness, will increase crop yield beyond current practices. Furthermore, we show that field practitioners can predict and manage agroecosystems for pollination services based on knowledge of just a few traits that are known for a wide range of flower visitor species. Editor's Choice
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| 3. |
- Rusch, Adrien, et al.
(författare)
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Flow and stability of natural pest control services depend on complexity and crop rotation at the landscape scale
- 2013
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Ingår i: Journal of Applied Ecology. - : Wiley. - 1365-2664 .- 0021-8901. ; 50:2, s. 345-354
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Tidskriftsartikel (refereegranskat)abstract
- Increasing landscape complexity can enhance biodiversity and ecosystem services in agroecosystems. However, policies based on conversion of arable land into semi-natural habitats to increase landscape complexity and ecosystem services can be difficult to implement. Although it appears to be a promising management option, nothing is known about the effect of increasing landscape diversity through crop rotations on the delivery of ecosystem services. In this study, we examined how landscape complexity and crop rotation intensity in the landscape at different spatial scales affect the flow and the stability of natural pest control services in barley fields using manipulative cage experiments. Exclusion experiments revealed that natural enemies can have a strong impact on aphid population growth and that the delivery of pest control services is strongly dependent on the landscape context. We found that the overall level of pest control increased with landscape complexity and that this effect was independent of crop rotation intensity. In addition, the within-field stability in pest control services increased with crop rotation intensity in the landscape, although stability in parasitism rates decreased. Multiple spatial scales analyses showed that the mean level of natural pest control was best predicted by landscape complexity at the 0 center dot 5-km and the 1-km spatial scales. The stability in overall pest control decreased with proportion of ley at the 2 center dot 5-km and the 3-km spatial scales. Synthesis and applications. Our study disentangled, for the first time, the relative effects of landscape complexity and crop rotation intensity on the delivery of an ecosystem service. We show that combined management of semi-natural habitat and crop rotation can stabilize and enhance natural pest control in agricultural landscapes. Our findings have important implications in terms of management options to maintain and enhance ecosystem services in agroecosystems. They suggest that conservation of heterogeneous landscapes, characterized by a higher proportion of semi-natural habitats such as pastures and relatively small fields, is essential for maintaining and enhancing effective biological control in agroecosystems.
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| 4. |
- Scheper, Jeroen, et al.
(författare)
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Local and landscape-level floral resources explain effects of wildflower strips on wild bees across four European countries
- 2015
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Ingår i: Journal of Applied Ecology. - : Wiley. - 1365-2664 .- 0021-8901. ; 52:5, s. 1165-1175
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Tidskriftsartikel (refereegranskat)abstract
- Growing evidence for declines in wild bees calls for the development and implementation of effective mitigation measures. Enhancing floral resources is a widely accepted measure for promoting bees in agricultural landscapes, but effectiveness varies considerably between landscapes and regions. We hypothesize that this variation is mainly driven by a combination of the direct effects of measures on local floral resources and the availability of floral resources in the surrounding landscape. To test this, we established wildflower strips in four European countries, using the same seed mixture of forage plants specifically targeted at bees. We used a before-after control-impact approach to analyse the impacts of wildflower strips on bumblebees, solitary bees and Red List species and examined to what extent effects were affected by local and landscape-wide floral resource availability, land-use intensity and landscape complexity. Wildflower strips generally enhanced local bee abundance and richness, including Red-listed species. Effectiveness of the wildflower strips increased with the local contrast in flower richness created by the strips and furthermore depended on the availability of floral resources in the surrounding landscape, with different patterns for solitary bees and bumblebees. Effects on solitary bees appeared to decrease with increasing amount of late-season alternative floralresources in the landscape, whereas effects on bumblebees increased with increasing early-season landscape-wide floral resource availability.Synthesis and applications. Our study shows that the effects of wildflower strips on bees are largely driven by the extent to which local flower richness is increased. The effectiveness of this measure could therefore be enhanced by maximizing the number of bee forage species in seed mixtures, and by management regimes that effectively maintain flower richness in the strips through the years. In addition, for bumblebees specifically, our study highlights the importance of a continuous supply of food resources throughout the season. Measures that enhance early-season landscape-wide floral resource availability, such as the cultivation of oilseed rape, can benefit bumblebees by providing the essential resources for colony establishment and growth in spring. Further research is required to determine whether, and under what conditions, wildflower strips result in actual population-level effects. Our study shows that the effects of wildflower strips on bees are largely driven by the extent to which local flower richness is increased. The effectiveness of this measure could therefore be enhanced by maximizing the number of bee forage species in seed mixtures, and by management regimes that effectively maintain flower richness in the strips through the years. In addition, for bumblebees specifically, our study highlights the importance of a continuous supply of food resources throughout the season. Measures that enhance early-season landscape-wide floral resource availability, such as the cultivation of oilseed rape, can benefit bumblebees by providing the essential resources for colony establishment and growth in spring. Further research is required to determine whether, and under what conditions, wildflower strips result in actual population-level effects.
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| 5. |
- Bommarco, Riccardo, et al.
(författare)
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Cereal aphid populations in non-crop habitats show strong density dependence
- 2007
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Ingår i: Journal of Applied Ecology. - : John Wiley & Sons. - 0021-8901 .- 1365-2664. ; 44:5, s. 1013-1022
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Tidskriftsartikel (refereegranskat)abstract
- 1.Few studies have addressed how density-dependent and density-independent regulation of population growth and abundance varies among habitats for a species that requires multiple habitat types to complete its life cycle. Understanding such relationships, however, are of direct relevance to the control of crop pest insects that regularly move between crop and non-crop habitats.2.We used autoregressive models to analyse a series of seasonal catches of the cereal aphid Rhopalosiphum padi. The data were collected from regional suction traps and egg counts on the overwintering host, over a period of 14–31 years, at four locations in Sweden. R. padi is an obligate host-alternating species in Sweden and seasonal catches reflect habitat use in a year: the primary woody host in winter and spring, the cereal crops in summer, and the perennial grasslands in the autumn.3.Strong direct density dependence acting within the year was found, but the strength varied between seasons depending on habitat use by the aphids during the year. Only a weak indication or no indication at all of density dependence was found during the period of residency on the primary host in the winter and spring periods.4.Density dependence occurred when R. padi utilized summer cereals (42% of the variation was explained), and even stronger density dependence occurred in the perennial grasslands in the autumn (70% variation explained). Stochastic fluctuations in the winter and spring were balanced by a strong density dependence in the cereal and grassland habitats in the summer and autumn periods, which reduced variability in population fluctuations.5.Weather, measured as seasonal average temperature and accumulated precipitation, did not affect aphid abundance fluctuations much, explaining only 1–9% of the variability.6.Synthesis and applications. Our results suggest that density-dependent regulation of R. padi occurs in late summer grasslands and early summer cereals. The mechanisms causing these patterns are not understood, making it difficult to provide specific pest management recommendations at this stage. The results do indicate, however, that pest management needs to involve a landscape-level approach, taking into account mechanistic information about the plant, herbivore and predator interactions in multiple habitats visited by the herbivorous pest.
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| 6. |
- Aguilera Nuñez, Guillermo, et al.
(författare)
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Organic fertilisation enhances generalist predators and suppresses aphid growth in the absence of specialist predators
- 2021
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Ingår i: Journal of Applied Ecology. - : Wiley. - 0021-8901 .- 1365-2664. ; 58, s. 1455-1465
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Tidskriftsartikel (refereegranskat)abstract
- Biological control by natural enemies is a valuable ecosystem service. The predator community in a crop field is a combination of predators dwelling in the field and those moving into it from the surrounding landscape. The former is mainly affected by field management, the latter more by the composition of the surrounding landscape. Yet, separate and combined effects of local and landscape management on pest suppression have seldom been investigated.We set-up mesocosms within an existing long-term agricultural field experiment to investigate the effects of local management of organic manure or inorganic mineral fertilisation, and simulated the spillover from the surrounding landscape of different predator types: no predators, generalist predators (wolf spiders) and specialist predators (ladybirds). We examined whether aphid density was driven by top-down or bottom-up processes under different fertilisation treatments, and how the magnitude of pest suppression was affected by predator community composition.We found positive synergistic effects between manure fertilisation and predator spillover on the suppression of aphid growth. Top-down suppression of aphids was more effective under manure fertilisation and in presence of specialist predators (ladybirds). Bottom-up effects on the plant biomass growth dominated in inorganically fertilised plots.Organic and inorganic fertilisation gave the same yield, but through different mechanisms. The abundance of locally emerging predators in the manure treatment increased top-down pest suppression yielding plant biomass levels comparable with inorganically fertilised plants, being the latter driven by bottom-up effects.Synthesis and applications. Organic fertilisation enhanced local emergence of predators increasing top-down pest suppression. In contrast, local predator communities were unable to suppress aphid populations in inorganic and no fertilisation treatments. Here, predator inflow from outside the crop field was essential for lowering aphid population growth. Managing landscapes to promote mobile predators emerges as particularly important for crop fields without manure amendments. We advise the active promotion of both local predators in the crop field and mobile predators in the landscape to secure the conservation of biological insect pest suppression.
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| 7. |
- Dániel-Ferreira, Juliana, et al.
(författare)
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Communities in infrastructure habitats are species rich but only partly support species associated with semi-natural grasslands
- 2023
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Ingår i: Journal of Applied Ecology. - : Wiley. - 0021-8901 .- 1365-2664. ; 60, s. 837-848
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Tidskriftsartikel (refereegranskat)abstract
- Biodiversity linked to traditionally managed semi-natural grasslands is declining, despite conservation efforts. At the same time, the area of novel grassland habitats along linear infrastructure, such as road verges and power line corridors, is increasing and in some regions surpass the area of semi-natural grasslands. An open question is to what extent these novel grasslands can complement or even replace traditionally managed grasslands as habitat for grassland species.We compared the alpha (species richness) and beta (abundance-based dissimilarities) diversity of plants, bumblebees and butterflies among semi-natural pastures, verges of small and big roads, power line corridors and uncultivated field borders nested within 32 landscapes (2 x 2 km squares). Landscapes had either high or low road density and were with or without power line corridors. Across landscapes there was also a gradient in the area of semi-natural pastures.Alpha diversity of all three species groups was as high in power line corridors and verges of small roads as in semi-natural pastures, regardless of landscape composition. Although all habitat types shared a large proportion of species, community composition differed among habitats for all three species groups. The beta diversity of plants and butterflies was driven primarily by the replacement of species (turnover), while the beta diversity of bumblebees was driven by a rarer occurrence of certain species in road verges (nestedness). This means that linear infrastructure habitats cannot fully replace the role of semi-natural grasslands for plant and pollinator diversity.The area of road verges, power line corridors and semi-natural pastures in the landscape influenced community composition of plants and butterflies, but not the similarity in community composition among habitats within landscapes.Policy implications. Although novel grasslands along linear infrastructures have high numbers of grassland species, they only support a part of the biodiversity found in traditionally managed semi-natural grasslands. Therefore, protecting and restoring semi-natural grasslands should continue to be a priority for the conservation of grassland biodiversity. However, especially in landscapes where the area of semi-natural grasslands is low, road verges and power line corridors can be important habitats for a number of grassland plants and insects and should be managed to promote biodiversity.
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| 8. |
- Riggi, Laura, et al.
(författare)
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Subsidy type and quality determine direction and strength of trophic cascades in arthropod food webs in agroecosystems
- 2019
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Ingår i: Journal of Applied Ecology. - : Wiley. - 0021-8901 .- 1365-2664. ; 56, s. 1982-1991
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Tidskriftsartikel (refereegranskat)abstract
- The subsidy hypothesis states that communities receiving nutrient subsidies will demonstrate top-down trophic cascades where predators indirectly increase plant biomass. This has been both confirmed and refuted, which might depend on whether the subsidy has mainly targeted the plant or the detrital food web compartment, and on the subsidy quality. This is particularly poorly understood for terrestrial communities such as heavily subsidized agroecosystems. Using cages covering 4 m(2) of ground in a long-term agricultural fertilization experiment, we tested whether subsidies targeting the detrital soil mesofauna compartment with organic fertilizers, or the plants with mineral fertilizer, impacted the direction and strength of trophic cascades in an arthropod-plant food web. We expected top-down controls of generalist arthropod predators (spiders, ground and rove beetles) on aphid densities to be stronger in organically fertilized plots due to enhanced alternative prey availability in the soil. Bottom-up control from barley quality on aphids was anticipated to be stronger in the mineral treatments. We examined how the quality (decomposability) of the organic subsidy governed the cascades by comparing treatments with labile (manure) and recalcitrant (hay) organic matter. Top-down forces dominated in food webs receiving organic subsidies, while bottom-up forces dominated under mineral fertilization. A high-quality, easily degradable organic subsidy propagated faster through the food chain, leading to a top-down trophic cascade with generalist predators having a positive effect on plant biomass in the labile but not in the recalcitrant organic treatment. Synthesis and applications. Management of agricultural soils that bolster the soil mesofauna, for example adding organic fertilizers, has potential to increase top-down biological control by naturally occurring generalist arthropod predators. Our research demonstrates how barley biomass can be enhanced in manure treatment in the presence of arthropod predators to a level comparable to that of mineral fertilizer.
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| 9. |
- Winqvist, Camilla, et al.
(författare)
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Mixed effects of organic farming and landscape complexity on farmland biodiversity and biological control potential across Europe
- 2011
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Ingår i: Journal of Applied Ecology. - : Wiley. - 0021-8901 .- 1365-2664. ; 48, s. 570-579
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Tidskriftsartikel (refereegranskat)abstract
- 5. Synthesis and applications. This Europe-wide study shows that organic farming enhanced the biodiversity of plants and birds in all landscapes, but only improved the potential for biological control in heterogeneous landscapes. These mixed results stress the importance of taking both local management and regional landscape complexity into consideration when developing future agri-environment schemes, and suggest that local-regional interactions may affect other ecosystem services and functions. This study also shows that it is not enough to design and monitor agri-environment schemes on the basis of biodiversity, but that ecosystem services should be considered too.
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