| 1. |
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| 2. |
- Birkhofer, Klaus, et al.
(författare)
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Relationships between multiple biodiversity components and ecosystem services along a landscape complexity gradient
- 2018
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Ingår i: Biological Conservation. - : Elsevier BV. - 0006-3207 .- 1873-2917. ; 218, s. 247-253
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Tidskriftsartikel (refereegranskat)abstract
- The assessment of effects of anthropogenic disturbance on biodiversity (BD) and ecosystem services (ES) and their relationships are key priorities of the Intergovernmental Panel for Biodiversity and Ecosystem Services. Agricultural landscapes and their associated BD provide multiple ES and it is crucial to understand how relationships between ES and BD components change along gradients of landscape complexity. In this study, we related eight ES potentials to the species richness of five invertebrate, vertebrate and plant taxonomic groups in cereal farming systems. The landscape complexity gradient ranged from areas dominated by annually tilled arable land to areas with high proportions of unfertilized, non-rotational pastures and uncultivated field borders. We show that after accounting for landscape complexity relationships between yield and bird richness or biological control became more positive, but relationships between bird richness and biological control became less positive. The relationship between bird and plant richness turned from positive to negative. Multidiversity (overall biodiversity), was positively related to landscape complexity, whereas multifunctionality (overall ES provision), was not significantly related to either one of these. Our results suggest that multidiversity can be promoted by increasing landscape complexity; however; we found no support for a simultaneous increase of several individual ES, BD components or multifunctionality. These results challenge the assumption that bio-diversity-friendly landscape management will always simultaneously promote multiple ES in agricultural landscapes. Future studies need to verify this pattern by using multi-year data, larger sets of ES and BD components and a study design that is appropriate to address larger spatial scales and relationships in several regions.
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| 3. |
- Gagic, Vesna, et al.
(författare)
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Interactive effects of pests increase seed yield
- 2016
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Ingår i: Ecology and Evolution. - : Wiley. - 2045-7758. ; 6, s. 2149-2157
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Tidskriftsartikel (refereegranskat)abstract
- Loss in seed yield and therefore decrease in plant fitness due to simultaneous attacks by multiple herbivores is not necessarily additive, as demonstrated in evolutionary studies on wild plants. However, it is not clear how this transfers to crop plants that grow in very different conditions compared to wild plants. Nevertheless, loss in crop seed yield caused by any single pest is most often studied in isolation although crop plants are attacked by many pests that can cause substantial yield losses. This is especially important for crops able to compensate and even overcompensate for the damage. We investigated the interactive impacts on crop yield of four insect pests attacking different plant parts at different times during the cropping season. In 15 oilseed rape fields in Sweden, we estimated the damage caused by seed and stem weevils, pollen beetles, and pod midges. Pest pressure varied drastically among fields with very low correlation among pests, allowing us to explore interactive impacts on yield from attacks by multiple species. The plant damage caused by each pest species individually had, as expected, either no, or a negative impact on seed yield and the strongest negative effect was caused by pollen beetles. However, seed yield increased when plant damage caused by both seed and stem weevils was high, presumably due to the joint plant compensatory reaction to insect attack leading to overcompensation. Hence, attacks by several pests can change the impact on yield of individual pest species. Economic thresholds based on single species, on which pest management decisions currently rely, may therefore result in economically suboptimal choices being made and unnecessary excessive use of insecticides.
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| 4. |
- Riggi, Laura, et al.
(författare)
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Pollen beetle mortality is increased by ground-dwelling generalist predators but not landscape complexity
- 2017
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Ingår i: Agriculture, Ecosystems and Environment. - : Elsevier BV. - 0167-8809 .- 1873-2305. ; 250, s. 133-142
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Tidskriftsartikel (refereegranskat)abstract
- Biological control of crop pests by naturally occurring arthropods depends on the entire community of natural enemies, but generalist predators and parasitoids are rarely considered in the same study. Also, the level of biological control in the field is affected by both within-field and landscape scale management. A multi-taxa approach that integrates multiple scales of management is needed to understand drivers for pest mortality. We examined local (weed cover and soil characteristics) and landscape (proportions of semi-natural and oilseed rape habitat) effects on natural enemy communities and biological control of pollen beetles in 15 oilseed rape (OSR) fields in Sweden. We found that agricultural intensification at the local (low weed cover) and landscape scale (low proportion of semi-natural area) increased evenness of generalist predators, but had no effect on the densities of pests and their natural enemies. This suggests that the generalist predators in OSR are well adapted to crop lands, at least within the examined gradient. Increasing OSR in the landscape decreased parasitoid densities and increased pest density, indicating a potential loss of pest control services by specialist natural enemies in landscapes with a high proportion of OSR. Finally, pollen beetle mortality increased with ground dwelling generalist predator abundance and soil clay content. Parasitism rates did not affect pest mortality, which is interesting as parasitoids have been considered major control agents in OSR. The hypothesis that increasing semi-natural habitat in the landscape enhances natural enemy abundances and species richness in agricultural landscapes was not supported. Local measures targeting generalist predators appear as a reasonable strategy to maximize pollen beetle control.
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| 5. |
- Rusch, Adrien, et al.
(författare)
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Agricultural landscape simplification reduces natural pest control: A quantitative synthesis
- 2016
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Ingår i: Agriculture, Ecosystems and Environment. - : Elsevier BV. - 0167-8809 .- 1873-2305. ; 221, s. 198-204
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Tidskriftsartikel (refereegranskat)abstract
- Numerous studies show that landscape simplification reduces abundance and diversity of natural enemies in agroecosystems, but its effect on natural pest control remains poorly quantified. Further, natural enemy impacts on pest populations have usually been estimated for a limited number of taxa and have not considered interactions among predator species. In a quantitative synthesis with data collected from several cropping systems in Europe and North America, we analyzed how the level and within-field spatial stability of natural pest control services was related to the simplification of the surrounding landscape. All studies used aphids as a model species and exclusion cages to measure aphid pest control. Landscape simplification was quantified by the proportion of cultivated land within a 1 km radius around each plot. We found a consistent negative effect of landscape simplification on the level of natural pest control, despite interactions among enemies. Average level of pest control was 46% lower in homogeneous landscapes dominated by cultivated land, as compared with more complex landscapes. Landscape simplification did not affect the amount of positive or negative interactions among ground dwelling and vegetation-dwelling predators, or the within-field stability of pest control. Our synthesis demonstrates that agricultural intensification through landscape simplification has negative effects on the level of natural pest control with important implications for management to maintain and enhance ecosystem services in agricultural landscapes. Specifically, preserving and restoring semi-natural habitats emerges as a fundamental first step to maintain and enhance pest control services provided by predatory arthropods to agriculture. (C) 2016 Elsevier B.V. All rights reserved.
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| 6. |
- 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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| 7. |
- Rusch, Adrien, et al.
(författare)
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Management intensity at field and landscape levels affects the structure of generalist predator communities
- 2014
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Ingår i: Oecologia. - : Springer Science and Business Media LLC. - 1432-1939 .- 0029-8549. ; 175:3, s. 971-983
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Tidskriftsartikel (refereegranskat)abstract
- Agricultural intensification is recognised as a major driver of biodiversity loss in human-modified landscapes. Several agro-environmental measures at different spatial scales have been suggested to mitigate the negative impact of intensification on biodiversity and ecosystem services. The effect of these measures on the functional structure of service-providing communities remains, however, largely unexplored. Using two distinct landscape designs, we examined how the management options of organic farming at the field scale and crop diversification at the landscape level affect the taxonomic and functional structure of generalist predator communities and how these effects vary along a landscape complexity gradient. Organic farming as well as landscapes with longer and more diversified crop rotations enhanced the activity-density of spiders and rove beetles, but not the species richness or evenness. Our results indicate that the two management options affected the functional composition of communities, as they primarily enhanced the activity-density of functionally similar species. The two management options increased the functional similarity between spider species in regards to hunting mode and habitat preference. Organic farming enhanced the functional similarity of rove beetles. Management options at field and landscape levels were generally more important predictors of community structure when compared to landscape complexity. Our study highlights the importance of considering the functional composition of generalist predators in order to understand how agro-environmental measures at various scales shape community assemblages and ecosystem functioning in agricultural landscapes.
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| 8. |
- Rusch, Adrien
(författare)
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Nutritional state of the pollen beetle parasitoid Tersilochus heterocerus foraging in the field
- 2013
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Ingår i: BioControl. - : Springer Science and Business Media LLC. - 1386-6141 .- 1573-8248. ; 58, s. 17-26
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Tidskriftsartikel (refereegranskat)abstract
- Many laboratory studies have demonstrated that parasitoids of various species depend on sugar sources such as nectar or honeydew. However, studies about nectar acquisition by parasitoids foraging in the field are scarce. Tersilochus heterocerus Thomson is one of the more abundant and widespread parasitoids of the pollen beetle (Meligethes aeneus F.) but nothing is known about the nutritional ecology of this species. In this study we examined the nutritional state of T. heterocerus at the time of emergence and at various time periods throughout the season while foraging in the field using high-performance anion-exchange chromatography. We found that: (i) T. heterocerus emerge with relatively small amounts of sugar, composed mainly of trehalose, glucose and fructose; (ii) the first parasitoids caught just after they appeared in the field at the beginning of oilseed rape flowering had already consumed significant amounts of sugar reserves; and (iii) the total amount of sugar at the end of flowering was always significantly higher than the total amount of sugar at the beginning of flowering. This study provides valuable insights into the acquisition of sugar in the field by the parasitoid T. heterocerus and suggests that nectar acquisition takes place in the oilseed rape field or in the surrounding landscape.
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| 9. |
- Rusch, Adrien, et al.
(författare)
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Predator body sizes and habitat preferences predict predation rates in an agroecosystem
- 2015
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Ingår i: Basic and Applied Ecology. - : Elsevier BV. - 1618-0089 .- 1439-1791. ; 16:3, s. 250-259
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Tidskriftsartikel (refereegranskat)abstract
- Top-down control of pest populations by their natural enemies is a crucial ecosystem service supporting agricultural production. The relationship between predator community composition and predation rates of pests remains poorly investigated. A deeper understanding of the processes shaping interaction strength in agroecosystems is needed if we are to accurately predict natural pest control services. Functional traits in a community can provide insights into processes shaping community assembly and ecosystem functioning. Functional diversity indices can be constructed from a single trait, such as body length, or from the integration of multiple traits, such as body length, hunting mode and habitat preference. However, their performance in predicting ecosystem functioning and services remains largely unexplored. We used empirical data replicated at landscape scales to examine which component of ground-dwelling predator community structure (activity-density, species richness, evenness, taxonomic distinctness and functional diversity) of spiders, carabids and staphylinids best predicted predation rates of aphids in spring cereals. Functional diversity explained a greater part of variation in predation rates than any other taxonomic or activity-density component. Among the indices for functional diversity, single-trait indices better predicted variation in aphid predation rates compared with multiple-trait indices. In particular, we found that the community-average value of body-size of ground-dwelling predators was negatively related to predation rates of aphids, whereas the proportion of spiders with a preference for arable land was positively related to predation rates. Additional analyses of body-size distributions of ground-dwelling predators suggested that intraguild predation was a key process shaping the relationship between predator community composition and the level of aphid pest control. Considering the functional trait composition of communities provides a more mechanistic understanding of the processes shaping the strength of trophic interactions in terrestrial ecosystems, thus improving predictive power. Body-size distribution and habitat preference appear to be particularly valuable in predicting the level of natural pest control by ground-dwelling predators in an agroecosystem.
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| 10. |
- Rusch, Adrien, et al.
(författare)
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Response of ground beetle (Coleoptera, Carabidae) communities to changes in agricultural policies in Sweden over two decades
- 2013
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Ingår i: Agriculture, Ecosystems and Environment. - : Elsevier BV. - 0167-8809 .- 1873-2305. ; 176, s. 63-69
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Tidskriftsartikel (refereegranskat)abstract
- Agricultural intensification has been recognized as an important driver of declines in biodiversity and ecosystem services. Changes in agricultural policy aims to mitigate these declines, but little is known about actual outcome of large scale changes in agricultural policy on communities of service-providing organisms. Two data sets containing captures of ground beetles (Carabidae) collected at an interval of 24 years were analyzed; the data were collected in the same area in Sweden under different environmental conditions before and after the introduction of a national pesticide risk reduction program. Environmental changes were analyzed by considering indicators of land use and agricultural management over time. Ground beetles collected over the whole season were considered and species were categorized according to functional traits. Environmental changes between the two time periods were characterized by increases in fallow and organic farming and a strong reduction in the amount of pesticide active ingredients sold and risk factors associated with pesticides. Although there were no changes in ground beetle species richness and community evenness after mitigation of agricultural intensification, there were differences in dominance distribution and functional composition. Ground beetles collected in the 1980s had higher proportions of carnivorous, cursorial, and small and intermediate size beetles than those collected in 2003. Communities sampled in 2003 had increased proportions of omnivorous, mobile, spring breeding, and large beetle species. These shifts in functional characteristics of ground beetle communities may improve biological control of cereal aphids and reduce variability in this ecosystem service over time. (C) 2013 Elsevier B.V. All rights reserved..
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