| 1. |
- Hanson, Helena, et al.
(författare)
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Agricultural Land Use Determines the Trait Composition of Ground Beetle Communities.
- 2016
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Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- In order to improve biological control of agricultural pests, it is fundamental to understand which factors influence the composition of natural enemies in agricultural landscapes. In this study, we aimed to understand how agricultural land use affects a number of different traits in ground beetle communities to better predict potential consequences of land-use change for ecosystem functioning. We studied ground beetles in fields with different agricultural land use ranging from frequently managed sugar beet fields, winter wheat fields to less intensively managed grasslands. The ground beetles were collected in emergence tents that catch individuals overwintering locally in different life stages and with pitfall traps that catch individuals that could have a local origin or may have dispersed into the field. Community weighted mean values for ground beetle traits such as body size, flight ability and feeding preference were estimated for each land-use type and sampling method. In fields with high land-use intensity the average body length of emerging ground beetle communities was lower than in the grasslands while the average body length of actively moving communities did not differ between the land-use types. The proportion of ground beetles with good flight ability or a carnivorous diet was higher in the crop fields as compared to the grasslands. Our study highlights that increasing management intensity reduces the average body size of emerging ground beetles and the proportion of mixed feeders. Our results also suggest that the dispersal ability of ground beetles enables them to compensate for local management intensities.
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| 2. |
- Hanson, Helena I., et al.
(författare)
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Agricultural land use affects abundance and dispersal tendency of predatory arthropods
- 2017
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Ingår i: Basic and Applied Ecology. - : Elsevier BV. - 1439-1791. ; 18, s. 40-49
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Tidskriftsartikel (refereegranskat)abstract
- Predatory arthropods contribute to biological control, but to become an integral part of agricultural management, it is essential to identify drivers of their spatio-temporal distribution at the landscape scale. This study focuses on how agricultural land use affects the community composition, emergence and dispersal tendency of predatory arthropods. The arthropods were collected in emergence traps during the growing season (14 weeks) in a gradient of agricultural land uses from intensively managed sugar beet fields, over winter wheat fields, to less intensively managed grasslands. The emergence traps were equipped with one pitfall trap and a collecting bottle at the top. The distribution of the arthropods between these two collecting methods was assumed to represent their tendency to move out of the habitat. The grasslands had the highest numbers of spiders, while the winter wheat fields had the highest numbers of omnivorous rove beetles and macropterous predaceous ground beetles. The phenology of emergence differed between the land-use types, resulting in seasonal differences in community composition. The overall dispersal tendency of predatory arthropods was higher in crop fields than in grasslands. This study suggests that only a diverse mix of agricultural land uses will provide high levels of predators from different functional groups, throughout the growing season.
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| 3. |
- Palmu, Erkki, et al.
(författare)
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Can δD and δ18O stable isotopes be used to detect long-range dispersal among carabid beetles?
- 2017
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Ingår i: Applied Soil Ecology. - : Elsevier BV. - 0929-1393. ; 119, s. 99-103
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Tidskriftsartikel (refereegranskat)abstract
- We studied if hydrogen (δD) and oxygen (δ18O) stable isotope values in three common carabid species in intensively managed agricultural landscapes in southernmost Sweden indicate long-range dispersal. We matched “emerging” (emergence tents) and “colonizing” (pitfall traps) individuals of three carabid species (Trechus quadristriatus, Harpalus rufipes, Pterostichus melanarius) to account for spatial and seasonal variability. There was higher dispersion of δD values among H. rufipes individuals as compared to values of the other two species, which suggests that H. rufipes individuals had the most variable spatial natal origin. The δD values were significantly lower among colonizing compared to emerging individuals in the flight capable and carnivorous species T. quadristriatus. This result suggests long-range migration of T. quadristriatus individuals from remote locations with deuterium depleted (lower δD) meteoric water. Our study provides a first effort towards understanding the δD and δ18O dynamics in epigean carabids in northern European agroecosystems. Additional research on larger (preferably continental) spatial scales and experimental trials that attempt to disentangle major unaccounted sources of variation and decoupling of δD and δ18O among carabids and other invertebrate natural enemies is urgently needed to allow a more frequent use of δD and δ18O dynamics as indicators of long-range dispersal.
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| 4. |
- Palmu, Erkki
(författare)
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Ground beetle dynamics in intensively managed agricultural landscapes
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In this thesis I have focused on studying dynamics of ground beetle assemblages in intensively managed agricultural landscapes. By definition, the land cover of these landscapes is dominated by annually tilled farmland, comprising a range of different crop types, in the context of the southern Swedish province of Scania mostly winter wheat, spring barley, winter rapeseed, and sugar beets. This background begs the question: can the presence of ground beetles in intensively managed agricultural landscapes be facilitated without sacrificing land dedicated to crop production? Crop diversification has been mentioned as a possible greening measure to mitigate agricultural intensity. Our results show that semi-natural grasslands and leys may not function as source habitats at a landscape-scale if they comprise a low proportion of the total land-use, while increasing crop diversity is correlated to ground beetle richness and diversity in agricultural landscapes dominated by arable land. Autumn breeding ground beetles were indicative of low crop diversity landscape. This is likely a result of high proportions of winter sown cereals that increase dominance of the species Pterostichus melanarius Illiger. Larger species were absent from assemblages emerging ground beetle assemblages in intensively managed crops such as sugar beet. Further, our results suggest that winter wheat fields are less adverse habitats for overwintering larger ground beetles as compared to sugar beet fields. Sugar beet management reduces emergence of larger ground beetle species that dominate actively moving assemblages, indicating that especially larger species are drivers of local ground beetle dynamics. Differences in isotopic composition between emerging and colonizing individuals of Trechus quadristriatus Schrank suggests that a significant proportion of individuals of this species came from remote locations, perhaps crossing the Baltic Sea with easterly winds.
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| 5. |
- Palmu, Erkki, et al.
(författare)
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Landscape-scale crop diversity interacts with local management to determine ground beetle diversity
- 2014
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Ingår i: Basic and Applied Ecology. - : Elsevier BV. - 1618-0089 .- 1439-1791. ; 15:3, s. 241-249
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Tidskriftsartikel (refereegranskat)abstract
- Crop diversification and maintenance of semi-natural habitats (grasslands and field boundaries) are suggested to enhance farmland biodiversity, but the relative importance of these factors remains poorly known. We evaluated how crop diversity and availability of semi-natural grasslands at a landscape-scale interacted with local farming management (three management types from low to high intensity: ley < winter wheat < sugar beet) in their effect on ground beetle assemblages in southern Sweden. Ground beetle diversity increased with crop diversity either independently of local management (Simpson species diversity), or only in the less intensively managed habitats (rarefied species richness). While ground beetle diversity in leys tended to increase with field boundary length, no such relationship was observed in winter wheat or sugar beet fields. In contrast, the landscape proportions of leys and semi-natural grasslands did not affect ground beetle species richness and diversity. We conclude that (a) semi-natural grasslands and leys may not function as source habitats at a landscape-scale if they comprise a low proportion of the total land-use, while (b) increasing crop diversity is correlated to ground beetle richness and diversity in agricultural landscapes dominated by arable land. The beneficial effect of landscape-scale crop diversification on farmland biodiversity may depend on the general level of agricultural intensity of a region.
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