| 1. |
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| 2. |
- Barin, Mohsen, et al.
(författare)
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Abundance of arbuscular mycorrhizal fungi in relation to soil salinity around Lake Urmia in northern Iran analyzed by use of lipid biomarkers and microscopy
- 2013
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Ingår i: Pedobiologia. - : Elsevier BV. - 1873-1511 .- 0031-4056. ; 56:4-6, s. 225-232
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Tidskriftsartikel (refereegranskat)abstract
- Saline soils around Lake Urmia in northern Iran constitute a stressed environment for plants and microbial communities, including arbuscular mycorrhizal (AM) fungi. Soil and root samples were collected from fields cultivated with the glycophytes Allium cepa L. and Medicago sativa L, and sites dominated by the halophyte Salicornia europaea L. Soil and root samples were analyzed for the AM fungal signature neutral lipid fatty acid (NLFA) 16:1 omega 5. The roots were also examined microscopically for mycorrhizal colonization. Each plant species was sampled across a salt gradient. Microscopic examination showed no AM fungal structures in the roots of S. europaea. The highest root colonization was recorded for M. sativa. The highest NLFA 16:1 omega 5 values were found in soil around M. sativa roots and the lowest in soil around S. europaea roots. We found evidence for stimulation of vesicle formation at moderate salinity levels in M. sativa, which is an indication of increased carbon allocation to mycorrhiza. On the other hand, we found a negative correlation between salinity and arbuscule formation in A. cepa, which may indicate a less functional symbiosis in saline soils. (C) 2013 Elsevier GmbH. All rights reserved.
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| 3. |
- Bokhorst, Stef Frederik, et al.
(författare)
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Contrasting responses of springtails and mites to elevation and vegetation type in the sub-Arctic
- 2018
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Ingår i: Pedobiologia. - : Elsevier. - 0031-4056 .- 1873-1511. ; 67, s. 57-64
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Tidskriftsartikel (refereegranskat)abstract
- Climate change is affecting the species composition and functioning of Arctic and sub-Arctic plant and soil communities. Here we studied patterns in soil microarthropod (springtails and mites) communities across a gradient of increasing elevation that spanned 450 m, across which mean temperature declined by approximately 2.5 degrees C, in sub-Arctic Sweden. Across this gradient we characterized microarthropod communities in each of two types of vegetation, i.e., heath and meadow, to determine whether their responses to declining temperature differed with vegetation type. Mite abundance declined with increasing elevation, while springtail abundance showed the opposite response. Springtail communities were dominated by larger species at higher elevation. Mite abundance was unaffected by vegetation type, while springtail abundance was 53% higher in the heath than meadow vegetation across the gradient. Springtails but not mites responded differently to elevation in heath and meadow vegetation; hemi-edaphic species dominated in the heath at higher elevation while epiedaphic species dominated in the meadow. Our results suggest that sub-Arctic mite and springtail communities will likely respond in contrasting ways to changes in vegetation and soil properties resulting from climate warming.
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| 4. |
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| 5. |
- Czernekova, Michaela, et al.
(författare)
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Evaluation of extraction methods for quantitative analysis of tardigrade populations in soil and leaf litter
- 2018
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Ingår i: Pedobiologia. - : Elsevier. - 0031-4056 .- 1873-1511. ; 70, s. 1-5
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Tidskriftsartikel (refereegranskat)abstract
- Accurate quantitative analysis of soil tardigrades depends on a relevant extraction method. Over the years, a number of different methods have been used, but the efficiency of these methods has rarely been evaluated for soil and leaf litter tardigrades. Four methods of extraction were compared in this study: the light-cooling (L-C) extractor, the high-gradient (H-G), Baermann extractor, the non-gradient (N-G) Baermann extractor and sieves.The results indicate that light and temperature are significant factors influencing tardigrade extraction. The L-C and H-G extractors were more effective than sieves for all substrate categories. These extraction methods (L-C and H-G) therefore seem to be appropriate for quantitative studies of soil and leaf litter tardigrades.
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| 6. |
- Czernekova, Michaela, et al.
(författare)
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Evaluation of extraction methods for quantitative analysis of tardigrade populations in soil and leaf litter
- 2018
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Ingår i: Pedobiologia. - : Urban und Fischer Verlag Jena. - 0031-4056 .- 1873-1511. ; 70, s. 1-5
-
Tidskriftsartikel (refereegranskat)abstract
- Accurate quantitative analysis of soil tardigrades depends on a relevant extraction method. Over the years, a number of different methods have been used, but the efficiency of these methods has rarely been evaluated for soil and leaf litter tardigrades. Four methods of extraction were compared in this study: the light-cooling (L-C) extractor, the high-gradient (H-G), Baermann extractor, the non-gradient (N-G) Baermann extractor and sieves.The results indicate that light and temperature are significant factors influencing tardigrade extraction. The L-C and H-G extractors were more effective than sieves for all substrate categories. These extraction methods (L-C and H-G) therefore seem to be appropriate for quantitative studies of soil and leaf litter tardigrades.
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| 7. |
- De Long, Jonathan, et al.
(författare)
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Nematode community resistant to deep soil frost in boreal forest soils
- 2016
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Ingår i: Pedobiologia. - : Elsevier BV. - 0031-4056 .- 1873-1511. ; 59:5-6, s. 243-251
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Tidskriftsartikel (refereegranskat)abstract
- As global climate change advances, shifts in winter precipitation are becoming more common in high latitude ecosystems, resulting in less insulating snow cover and deeper soil frost. Long-term alterations to soil frost can impact on ecosystem processes such as decomposition, microbial activity and vegetation dynamics. In this study we utilized the longest running, well-characterized soil frost manipulation experiment in a boreal forest. We measured nematode family composition and feeding group abundances at four different soil layer depths from plots that had been subjected to deep soil frost for one and 11 years. The overall abundance of nematodes and the different feeding groups were unaffected by deep soil frost. However, a higher Maturity Index was weakly associated with deep soil frost (indicative of lower nutrient enrichment and more persister nematode (i.e., K-strategist) families), likely due to the loss of nutrients and reduced inputs from inhibited decomposition. Multivariate and regression analyses showed that most nematode families were weakly associated with dominant understory plant species and strongly associated with soil organic matter (SOM). This is probably the result of higher resource availability in the control plots, which is favorable to the nematode community. These results indicate that the nematode community was more strongly driven by the long-term indirect effects of deep soil frost on SOM as opposed to the direct effects. Our findings highlight that the indirect effects of altered winter precipitation and soil frost patterns may be more important than direct winter climate effects. Further, such indirect effects on SOM and the plant community that may affect the nematode community can only be seen in long-term experiments. Finally, given the critical role nematodes play in soil food webs and carbon and nutrient cycling, our results demonstrate the necessity of considering the response of nematodes to global climate change in boreal forest soils.
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| 8. |
- De Smedt, Pallieter, et al.
(författare)
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Forest edges reduce slug (but not snail) activity-density across Western Europe
- 2019
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Ingår i: Pedobiologia. - : Elsevier BV. - 0031-4056 .- 1873-1511. ; 75, s. 34-37
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Tidskriftsartikel (refereegranskat)abstract
- Fragmentation strongly shapes the distribution of organisms within forest patches through contrasting environmental conditions between the edge and interior habitat. Edge-to-interior distribution patterns are, however, poorly studied for litter- and soil-dwelling fauna, such as terrestrial gastropods, despite their high densities and significant impact on ecosystem processes, as both herbivores and detritivores. Therefore, we investigated edge-to-interior abundance patterns of terrestrial gastropods in 224 fragmented forest patches across Western Europe. Catching over 15,000 gastropods, we found that slug abundance is reduced in forest edges, while snail abundance shows no response on the edge effect. We hypothesize that these patterns could be explained by higher drought tolerance of snails, since forest edges have reduced air and soil humidity and elevated temperatures compared to forest interiors. Reduced slug abundance in forest edges potentially has ecological consequences for herbivory in and outside forest patches and nutrient cycling.
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| 9. |
- Friberg, Hanna, et al.
(författare)
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Effect of earthworms and incorporation of grass on Plasmodiophora brassicae
- 2008
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Ingår i: Pedobiologia. - : Elsevier BV. - 1873-1511 .- 0031-4056. ; 52:1, s. 29-39
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Tidskriftsartikel (refereegranskat)abstract
- The resting spores of Plasmodiophora brassicae, causal agent of clubroot disease of crucifers, are tolerant structures with the abitity to survive for at least 15 years in soil waiting for a host. The influence of incorporation of cut grass (Lolium perenne) and presence of the earthworm Aporrectodea caliginosa on R brassicae resting spores was investigated in a microcosm experiment, and measured as disease development in susceptible bait plants (Brassica rapa var. pekinensis). Grass material was incorporated every other month during 498 days of experiment, and soil samples for P brassicae bioassay were collected nine times, just before each incorporation of grass. The grass treatment, irrespective of earthworm presence, resutted in a tower soil pH, increased the proportion of large soil. aggregates and increased the abundance of mites, collembolans and nematodes. The microbial biomass (SIR) was increased by grass incorporation, as a result of an increase in growing microbial biomass. When earthworms were present, the response of the microbial community was more pronounced, and the organic material. was mineralised more efficiently, leading to a higher percentage ash content of the soil. In contrary to these changes, clubroot disease severity did not differ among the treatments at any specific sampling. Across all samplings, however, disease severity was higher in the grass treatment without earthworms compared with the control treatment. The result contradicts earlier studies on earthworm effects on P brassicae. The importance of different earthworm species on the interaction is discussed. (c) 2008 Elsevier GmbH. All rights reserved.
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| 10. |
- Ingimarsdottir, Maria, et al.
(författare)
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Food sources of early colonising arthropods: The importance of allochthonous input
- 2014
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Ingår i: Pedobiologia. - : Elsevier BV. - 1873-1511 .- 0031-4056. ; 57:1, s. 21-26
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Tidskriftsartikel (refereegranskat)abstract
- Arthropod predators and detritivores are among the first colonisers on land surfaces undergoing primary succession. In the absence of higher plants and herbivores, they may either have an allochthonous food source (i.e. of geographically distant origin) or local food source that is sustained by e.g. microorganisms. By studying spiders and collembolans on sites along chronosequences on recently emerged nunataks (ice-free land in glacial areas), we analysed whether the food source of early colonisers was of local or distant origin. Also, we measured the potential changes in trophic position with increasing site age. With stable carbon and nitrogen isotope analysis of both spiders and collembolans, we determined that allochthonous food sources are important on the youngest sites. The allochthonous food sources may explain how arthropods can persist in the absence of local primary productivity. Also, some spider species may increase their ability to survive by shifting their trophic position as the community composition changes. The results indicate that a wolf spider species shifted towards a lower trophic level with increasing site age. By contrast, no shifts in trophic position were observed for sheet-web spiders or collembolans.
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| 11. |
- Sereda, Elvira, et al.
(författare)
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Spatial distribution of spiders and epedaphic Collembola in an environmentally heterogeneous forest floor habitat
- 2012
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Ingår i: Pedobiologia. - : Elsevier BV. - 1873-1511 .- 0031-4056. ; 55:5, s. 241-245
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Tidskriftsartikel (refereegranskat)abstract
- Describing the biotic and abiotic processes that are responsible for the formation of spatial patterns in predators and their prey is crucial for improving our understanding of food-web interactions. We studied the spatial distribution of four abundant spider species and three common groups of epedaphic Collembola prey in a beech-dominated (Fagus sylvatica) forest floor habitat and related the observed patterns to environmental heterogeneity, overall predator activity (all ground beetles and spiders) and prey availability (all Collembola) at the local scale. Spiders and epedaphic Collembola were sampled over 392 days in a spatially explicit design based on a regular grid of 25 pitfall traps (inter-trap distance 100 m). Environmental heterogeneity was characterized by cover of moss and litter as well as the amount of dead wood at each trap location. We first used the index of dispersion to characterize the spatial distribution of spider species and Collembola and then related the observed patterns to environmental heterogeneity, predator and prey availability while testing for spatial autocorrelation within the same models. All taxa were significantly more aggregated than expected from the assumption of random distribution. The distribution of spider species was positively (Coelotes terrestris) or negatively (Tenuiphantes zimmermanni and Tapinocyba insecta) related to the cover of moss and negatively related to litter cover (C. terrestris) or the local availability of prey (T. insecta). The distribution of Collembola was negatively related to local litter cover (Lepidocyrtus spp.) and positively related to the amount of medium deadwood pieces (all other Entomobryidae). Our study suggests that none of the spider species preferred areas of low overall predator activity density. Moreover, it does not indicate association of spider species to prey-rich areas at the analyzed scale of WO m. It further highlights the importance of environmental heterogeneity, as different habitat properties differentially affected the local activity density of spiders and Collembola and thus considerably contributed to the understanding of distribution patterns. (c) 2012 Elsevier GmbH. All rights reserved.
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| 12. |
- Sohlenius, B, et al.
(författare)
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Occurrence of nematodes, tardigrades and rotifers on ice-free areas in East Antarctica
- 2004
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Ingår i: Pedobiologia. - : Elsevier BV. - 1873-1511 .- 0031-4056. ; 48:4, s. 395-408
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Tidskriftsartikel (refereegranskat)abstract
- Nematodes, rotifers and tardigrades were collected on three nunataks (mountain peaks penetrating the ice sheet) in Vestfjella, on six nunataks; in Heimefrontfjella and on the Schirmacher Oasis in East Antarctica in the austral summers of 1996/97 and 2001/02. Most samples were taken on the nunatak Basen in Vestfjella where the Swedish station Wasa is located. The microfauna was patchily distributed and the highest densities of animals were found on sites with visible vegetation of mosses, lichens or algae. Thirty-four taxa of nematodes and tardigrades were found. Only seven of these occurred regularly in apparently actively reproducing populations. Other occasional records of nematodes had very few specimens. The highest number of species was found on the nunatak Basen. Rotifers, found in 66% of the samples, were the most frequent animal group. Nematodes occurred in 37% of the samples and tardigrades in 42%. The most frequent nematodes were Plectus and Panagrolaimus, occurring in 26% and 5% of the samples, respectively. Macrobiotus, Hebesuncus and Acutuncus were the most frequent and abundant tardigrades. The pattern of animal distribution can be related to both habitat characteristics and to the geographic position of the nunatak. The communities are little organised and the distribution of the fauna has similarities with an early phase of colonisation. (C) 2004 Elsevier GmbH. All rights reserved.
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| 13. |
- Terhivuo, J., et al.
(författare)
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Clonal diversity and morphometry in the parthenogenetic earthworm Eiseniella tetraedra (Sav.) as affected by habitat characteristics including radioactive pollution
- 2011
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Ingår i: Pedobiologia. - : Elsevier BV. - 0031-4056 .- 1873-1511. ; 54, s. S11-S18
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Tidskriftsartikel (refereegranskat)abstract
- Eiseniella tetraedra (Sav.) is a cosmopolitan earthworm reproducing by obligate parthenogenesis. Here, we examined whether habitat characteristics affected the clone pool diversities and morphometric variability of the stenotopic riparian species E. tetraedra along a west-east transect from the Scandinavian mountains to lowland habitats of the Swedish east coast through Finland and to Russia (the Komi Republic) near the Ural Mountains. The transect comprised a geographical distance that cuts through the maritime to continental climatological zones within the boreal forest belt. It terminated in the Komi Republic, thus adding habitat (soil) characteristics to the factor of radioactive pollution. We found that mountain brooks in Sweden hosted the lowest numbers of clones, but in the lowland samples the clone pool diversities decreased in general from Sweden through Finland and Russia, i.e. from west to east. Nevertheless, high levels of clonal variability were observed within the countries, so that even monomorphic pools were found. However, no clones were shared between the countries. The fresh body weights and posterior body lengths of adult earthworms decreased from west to east. The numbers of posterior segments did not, however, differ between the countries, clue to decreased segment size. The location of the clitellum, tubercula pubertatis and male pores showed no clear-cut morphometric clines along the W-E gradient, but the tubercula pubertatis and male pores were more clearly demarcated in adults of the Russian material than in those from the West. Eiseniella adults from the Swedish mountains carried spermatophores considerably more often than those from the other localities. E. tetraedra from localities with radioactive pollution in Russia (the Komi Republic) showed no clear-cut clone pool diversities in comparison to the clone pools of the other sites within the area. Monomorphic clone pools were recorded in localities with low as well as high levels of long-term ionizing radiation and exposure to heavy metals. We found no morphological malformations, such as dislocations of characters, in comparison to individuals from sites with lower levels of environmental radiation.
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| 14. |
- Terhivuo, Juhani, et al.
(författare)
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Clone distribution of the earthworm Eiseniella tetraedra (Sav.) (Oligochaeta : Lumbricidae) across an altitudinal gradient on subarctic mountains of NW Europe
- 2008
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Ingår i: Pedobiologia. - Jena : Elsevier. - 0031-4056 .- 1873-1511. ; 51:5-6, s. 375-384
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Tidskriftsartikel (refereegranskat)abstract
- In earlier studies, we have shown that clone diversity of the parthenogenetic earthworm Eiseniella tetraedra increases from the upper reaches of rivers in northern Sweden towards their mouths. Now we survey brooks in the Scandes Mountains in the watershed between Sweden and Norway where major rivers originate. Using starch get enzyme electrophoresis, we found 37 clones in a total catch of 379 individuals from six mountains. The most abundant clone made up 48.3% of the individuals collected. It was present on most mountains and was found at different elevations. In comparison with other clones it may represent a general-purpose genotype adapted to environmental conditions ranging from alpine through to subalpine to boreal habitats in the mountains. Diversity of clone assemblages decreased with increasing elevation. On four mountains, one to two clones were found at higher elevations. Passive downstream dispersal of E. tetraedra propagules from wider areas of the mountains was responsible for the more diverse clone pools in the tower reaches of the brooks (i.e., "small rivers behave like large ones"). Two clone groups, which deviated from the norm clone in their number of enzyme variants, were evenly distributed among different elevations. Therefore, we could not correlate genotype differences (i.e., adaptation of clones to mountain elevations). Clone pool similarities among the mountains were tow on average (range 0-58%) but in a cluster of four mountains, similarities varied from 46% to 58%. Clone pool similarities between different elevations of the same mountain ranged from 27% to 83%. One mountain brook was sampled over 3 years to assess clone turnover. Only the norm clone was found in upstream habitats but it and three other clones were recorded downstream in at least 2 years. Ten clones were found once in the latter habitat as well.
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| 15. |
- Vucic-Pestic, Oliver, et al.
(författare)
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Habitat structure and prey aggregation determine the functional response in a soil predator-prey interaction
- 2010
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Ingår i: Pedobiologia. - : Elsevier BV. - 1873-1511 .- 0031-4056. ; 53:5, s. 307-312
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Tidskriftsartikel (refereegranskat)abstract
- Functionalresponses describe the per capita consumption rates of predators depending on prey density, which quantifies the energy transfer between trophic levels. We studied a typical interaction of the litter–soil systems between hunting spiders (Pardosa lugubris; Araneae: Lycosidae) and springtails (Heteromurus nitidus; Collembola: Entomobryidae) at varying habitatstructure, i.e. with moss vs. without moss. We found a hyperbolic increase in consumption (functionalresponse type II) in the treatment without habitatstructure that was converted into a roller-coaster (or dome-shaped in a broad sense) functionalresponse in treatments with habitatstructure. Additional experiments suggest that the reduced per capita consumption rates at high prey densities may be explained by aggregative defence behaviour of the springtails. Experimentally, this behaviour was induced by the presence of habitatstructure. We analyzed the net-energy gain of this predator–preyinteraction by comparing the predator’s metabolic energy loss to its energy gain by consumption. In treatments with habitatstructure, the net-energy gain of the predator was limited at intermediate prey densities where preyaggregation reduced the consumption rates. Our results stress the importance of habitatstructure and prey behaviour in shaping the functionalresponse in a typical soil–litter predator–preyinteraction.
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| 16. |
- Williams, Alwyn, et al.
(författare)
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Above- and below-ground interactions with agricultural management: Effects of soil microbial communities on barley and aphids
- 2014
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Ingår i: Pedobiologia. - : Elsevier BV. - 1873-1511 .- 0031-4056. ; 57:2, s. 67-74
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Tidskriftsartikel (refereegranskat)abstract
- Recent research has shown that agricultural management affects microbial biomass and community composition. We investigated the functional implications of such effects in terms of barley biomass production and nutrient acquisition, and whether changes in barley nutrient status affected aphid fecundity. Soils were collected from conventional, ley and organic arable fields and used as inocula in a glasshouse experiment. We determined microbial biomass and community composition using PLFA. We investigated barley growth and nutrient responses to the different soil inoculums, and the impact of excluding arbuscular mycorrhizal fungi (AMF). Aphids were applied to plants within clip cages and numbers of offspring counted. Microbial biomass and community composition were unaffected by agricultural management. The microbial communities altered root and shoot biomass and nutrient allocation, but had no effect on grain yield. Exclusion of AMF significantly increased shoot biomass but reduced grain yield. Aphid fecundity was not significantly affected by the microbial community or shoot nitrogen. We conclude that agricultural intensification does not necessarily have negative consequences for above- and below-ground interactions, and microbial communities from conventionally managed soils may offer equal benefit to crop productivity and nutrition as those from organically managed soils. (C) 2014 Elsevier GmbH. All rights reserved.
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| 17. |
- Sjöqvist, Erik
(författare)
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Nonadiabatic holonomic single-qubit gates in off-resonant Λ systems
- 2016
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Ingår i: Physics Letters A. - : Elsevier BV. - 0375-9601 .- 1873-2429. ; 380:1-2, s. 65-67
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Tidskriftsartikel (refereegranskat)abstract
- We generalize nonadiabatic holonomic quantum computation in a resonant Λ configuration proposed in [New J. Phys. 14 (2012) 103035] to the case of off-resonant driving lasers. We show that any single-qubit holonomic gate can be realized by separately varying the detuning, amplitude, and phase of the lasers.
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| 18. |
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| 19. |
- Campbell, Colin
(författare)
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Predictors of fine-scale spatial variation in soil mite and microbe community composition differ between biotic groups and habitats
- 2012
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Ingår i: Pedobiologia. - : Elsevier BV. - 0031-4056. ; 55, s. 83-91
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Tidskriftsartikel (refereegranskat)abstract
- Soils support highly diverse communities, but due to the great spatial complexity at very fine scales and small size of soil organisms, our knowledge of what structures belowground communities remains limited. We used a spatially nested sampling regime (distances between samples of 0.06-122 m) to develop an understanding of the relationship between soil mite and microbial community composition and properties of vegetation and underlying soil within two habitats: birch woodland and heather moorland. We found that variation in community composition of all four biotic groups investigated (Oribatida, Mesostigrnata, fungi and bacteria - thus representing multiple trophic levels) was related to variation in soil properties and vegetation, but also space. These three factors (i.e. vegetation, soil properties and space) accounted for 17-36% of the variation in community composition of the biotic groups. The remaining, rather large, proportion of unexplained variation in community composition (64-87%) is likely to represent either random variation or variation related to unmeasured variables that are not spatially auto-correlated. Soil properties generally explained more variance in belowground communities than could vegetation composition. This should not be interpreted as evidence that soil properties exert a greater influence on belowground communities than vegetation composition per se, as the vegetation composition within a habitat is likely to vary at a larger spatial scale than the soil properties we measured. Vegetation composition had stronger explanatory power in the birch woodland and was more strongly related to fungal community composition than that of any other biotic group, particularly in heather moorland. This relationship may reflect the strong association between plants and their fungal symbionts and pathogens. We conclude that both vegetation composition and variation in soil properties influence belowground communities. However, the relative importance of these two factors depends on both habitat and the type of organism being studied. (c) 2011 Elsevier GmbH. All rights reserved.
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| 20. |
- Hall, Maria, et al.
(författare)
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The predatory mite Hypoaspis aculeifer is attracted to food of its fungivorous prey
- 1999
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Ingår i: Pedobiologia. - 0031-4056. ; 43:1, s. 11-17
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Tidskriftsartikel (refereegranskat)abstract
- To locate a prey a predator may rely on information originating from the habitat or the food of the prey, from the prey itself or its feeding activities. This study examines the origin of information used by the soil living predatory mite Hypoaspis aculeifer (Canestrini) when foraging for a fungivorous collembolan prey Folsomia f metaria (L.). Preference experiments were performed in Petri dishes, where the mite chose between fungal or agar cores with or without prey traces. The mite was attracted to fungi, but not to prey-related cues or other cues induced by grazing of collembolans. This suggests a foraging strategy of a generalist predator that mainly relies on fungal stimuli that lead to an area, where the probability of encountering fungivorous prey is high.
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| 21. |
- Keller, Thomas
(författare)
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Decreased burrowing activity of endogeic earthworms and effects on water infiltration in response to an increase in soil bulk density
- 2021
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Ingår i: Pedobiologia. - : Elsevier BV. - 0031-4056. ; 85-86
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Tidskriftsartikel (refereegranskat)abstract
- Endogeic earthworms live and burrow in the soil to find their food. They burrow by pushing the soil aside or ingesting it and are thus sensitive to soil compaction. However there is a scarcity of data regarding the effects of soil bulk density on the burrowing behavior and activity of endogeic earthworms. We carried out laboratory experiments using repacked soil cores with various levels of bulk density (from 1.18 to 1.38 g cm-3) in which individuals of Aporrectodea caliginosa or Allolobophora chlorotica were incubated for six weeks. The burrow systems inside the soil cores and the compaction around the burrows were then analyzed using X-ray tomography. Soil water infiltration measurements were also carried out. The increase in bulk density had a negative impact on all burrow system characteristics (length, volume, diameter, continuity, number of burrows). When bulk density increased from 1.18 to 1.38 g cm-3, volume, diameter, continuity and the number of burrows decreased on average by 77 %, 21 %, 81 % and 58 %, respectively. The increase in density due to compaction around the burrows was similar whatever the species and the bulk density. Increasing soil bulk density from 1.18 to 1.38 g cm-3 also greatly decreased water infiltration (-89 % for both species) and increased breakthrough time (10 and 25-fold for A. chlorotica and A. caliginosa respectively). However, compared to a control without earthworms, water infiltration in cores incubated with endogeic species was only increased significantly at 1.18 and 1.23 g cm-3. This illustrates that burrows made by endogeic earthworms moderately increase water infiltration and only when the soil bulk density is low. Data provided in this study could be used to refine simulation models of earthworm burrowing behavior where burrowing is assumed to be mainly governed by soil water content, temperature and soil bulk density.
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| 22. |
- Martinsson, Svante, 1985, et al.
(författare)
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Cryptic diversity in the well-studied terrestrial worm Cognettia sphagnetorum (Clitellata: Enchytraeidae)
- 2014
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Ingår i: Pedobiologia. - : Elsevier BV. - 0031-4056. ; 57:1, s. 27-35
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Tidskriftsartikel (refereegranskat)abstract
- The terrestrial worm Cognettia sphagnetorum has been used as a model in several studies focusing on research areas such as climate change as well as forest and soil ecology; it has also been shown to play a key role in the decomposition of organic matter and nutrient cycling. Cognettia is an enchytraeid genus commonly found in acidic terrestrial habitats, such as coniferous forests and bogs. In this study, the diversity of the genus, with particular focus on the morphospecies C. sphagnetorum in northern Europe, is assessed using four molecular markers, the mitochondrial COI (cytochrome c oxidase subunit I) and16S (16S ribosomal RNA), and the nuclear H3 (Histone 3) and ITS (Internal Transcribed Spacer). The datasets were first delimited into Molecular Operational Units (MOTUs) and the existence of global barcoding-gaps was tested. Single gene-trees were then estimated for all genes using Bayesian Inference, and a species tree was estimated with all markers combined using the multi-species coalescence. The results show that in northern Europe the genus consists of at least eight MOTUs supported by all genes except H3. Four of these MOTUs were within the morphotaxon C. sphagnetorum and two within Cognettia glandulosa. C. sphagnetorum s.l. was found to be non-monophyletic in all gene-trees, as well as in the species tree. As the MOTUs were well separated and non-monophyly was observed within C. sphagnetorum s.l., we conclude that the MOTUs are best treated as separate species. Given that cryptic diversity was found in this genus, we recommend that material of Cognettia used in future studies should be identified using molecular barcodes.
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| 23. |
- Menkis, Audrius
(författare)
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Edaphic properties related with changes in diversity and composition of fungal communities associated with Pinus radiata
- 2018
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Ingår i: Pedobiologia. - : Elsevier BV. - 0031-4056. ; 66, s. 43-51
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Tidskriftsartikel (refereegranskat)abstract
- Effective symbiosis with ectomycorrhizal (ECM) fungi is important for the successful growth and establishment of Pinus radiata. However, the structure of ECM communities varies across soil (edaphic) and environmental conditions, and thus affects the potential range of symbiotic associations. To improve our understanding of these factors, we characterised the range of ECM fungi present across six sites varying in edaphic properties. We also assessed ECM fungi in root tips of P. radiata planted two years earlier at these sites to assess the extent in overlap between root and soil ECM communities. The structure of the ECM community varied substantially with site. Across all sites, correlations were identified between soil pH and metrics describing ECM community structure in both soil and root samples, indicating soil pH was contributing to the differences in the fungal communities between sites. Mineralisable nitrogen, soil carbon, and phosphorus content also varied with site, but were not significantly related to descriptors of the ECM communities. Root tips and surrounding soils shared some taxa but were inhabited by diverse communities of fungi, and a number of ECM P. radiata associations unique to New Zealand were identified. It is possible that the establishment of linkages between metrics could provide an opportunity to begin predicting the response of ECM populations to site modification, and potentially increase the growth of radiata pine and improve forest health through enhanced resilience to disturbance.
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| 24. |
- Nyström, Kaj, 1969-, et al.
(författare)
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Extension properties and boundary estimates for a fractional heat operator
- 2016
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Ingår i: Nonlinear Analysis. - : Elsevier BV. - 0362-546X .- 1873-5215. ; 140, s. 29-37
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Tidskriftsartikel (refereegranskat)abstract
- The square root of the heat operator $\sqrt{\partial_t-\Delta}$, can be realized as the Dirichlet to Neumann map of the heat extension of data on $\mathbb R^{n+1}$ to $\mathbb R^{n+2}_+$. In this note we obtain similar characterizations for general fractional powers of the heat operator, $(\partial_t-\Delta)^s$, $s\in (0,1)$. Using the characterizations we derive properties and boundary estimates for parabolic integro-differential equations from purely local arguments in the extension problem.
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| 25. |
- Thunberg, Johan, et al.
(författare)
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Consensus and formation control on SE (3) for switching topologies
- 2016
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Ingår i: Automatica. - : Elsevier. - 0005-1098 .- 1873-2836. ; 66, s. 109-121
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Tidskriftsartikel (refereegranskat)abstract
- This paper addresses the consensus problem and the formation problem on SE(3) in multi-agent systems with directed and switching interconnection topologies. Several control laws are introduced for the consensus problem. By a simple transformation, it is shown that the proposed control laws can be used for the formation problem. The design is first conducted on the kinematic level, where the velocities are the control laws. Then, for rigid bodies in space, the design is conducted on the dynamic level, where the torques and the forces are the control laws. On the kinematic level, first two control laws are introduced that explicitly use Euclidean transformations, then separate control laws are defined for the rotations and the translations. In the special case of purely rotational motion, the consensus problem is referred to as consensus on SO(3) or attitude synchronization. In this problem, for a broad class of local representations or parameterizations of SO(3), including the Axis-Angle Representation, the Rodrigues Parameters and the Modified Rodrigues Parameters, two types of control laws are presented that look structurally the same for any choice of local representation. For these two control laws we provide conditions on the initial rotations and the connectivity of the graph such that the system reaches consensus on SO(3). Among the contributions of this paper, there are conditions for when exponential rate of convergence occurs. A theorem is provided showing that for any choice of local representation for the rotations, there is a change of coordinates such that the transformed system has a well known structure.
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| 26. |
- Abazov, V. M., et al.
(författare)
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Measurement of sigma(p(p)over-bar -> Z plus X)Br(Z -> tau(+)tau(-)) at root s=1.96 TeV
- 2009
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 670:4-5, s. 292-299
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Tidskriftsartikel (refereegranskat)abstract
- We present a measurement of the cross section for Z boson production times the branching fraction to tau lepton pairs sigma(p (p) over bar -> Z + X)Br(Z -> tau(+)tau(-)) in p (p) over bar collisions at root s = 1.96 TeV. The measurement is performed in the channel in which one tau lepton decays into a muon and neutrinos. and the other tau lepton decays hadronically or into an electron and neutrinos. The data sample corresponds to an integrated luminosity of 1.0 fb(-1) collected with the DO detector at the Fermilab Tevatron Collider. The sample contains 1511 candidate events with an estimated 20% background from jets or muons misidentified as tau leptons. We obtain sigma . Br = 240 +/- 8 (star) +/- 12 (sys) +/- 15 (lum) pb, which is consistent with the standard model prediction.
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| 27. |
- Matura, M, et al.
(författare)
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Selected oxidized fragrance terpenes are common contact allergens
- 2005
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Ingår i: Contact Dermatitis. - : Wiley. - 0105-1873 .- 1600-0536. ; 52:6, s. 320-328
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Tidskriftsartikel (refereegranskat)abstract
- Terpenes are widely used fragrance compounds in fine fragrances, but also in domestic and occupational products. Terpenes oxidize easily due to autoxidation on air exposure. Previous studies have shown that limonene, linalool and caryophyllene are not allergenic themselves but readily form allergenic products on air-exposure. This study aimed to determine the frequency and characteristics of allergic reactions to selected oxidized fragrance terpenes other than limonene. In total 1511 consecutive dermatitis patients in 6 European dermatology centres were patch tested with oxidized fragrance terpenes and some oxidation fractions and compounds. Oxidized linalool and its hydroperoxide fraction were found to be common contact allergens. Of the patients tested, 1.3% showed a positive reaction to oxidized linalool and 1.1% to the hydroperoxide fraction. About 0.5% of the patients reacted to oxidized caryophyllene whereas 1 patient reacted to oxidized myrcene. Of the patients reacting to the oxidized terpenes, 58% had fragrance-related contact allergy and/or a positive history for adverse reaction to fragrances. Autoxidation of fragrance terpenes contributes greatly to fragrance allergy, which emphasizes the need of testing with compounds that patients are actually exposed to and not only with the ingredients originally applied in commercial formulations.
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| 28. |
- Bråred Christensson, Johanna, 1965, et al.
(författare)
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Linalool - a significant contact sensitizer after air exposure
- 2010
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Ingår i: Contact Dermatitis. - : Wiley. - 0105-1873 .- 1600-0536. ; 62:1, s. 32-41
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Tidskriftsartikel (refereegranskat)abstract
- Background: Linalool is a widely used fragrance terpene. Pure linalool is not allergenic or a very weak allergen, but autoxidizes on air exposure and the oxidation products can cause contact allergy. Oxidized (ox.) linalool has previously been patch tested at a concentration of 2.0% in petrolatum (pet.) in 1511 patients, and 1.3% positive patch test reactions were observed. Objective: To investigate the optimal patch test concentration for detection of contact allergy to ox. linalool. Methods: Four concentrations of ox. linalool (2.0%, 4.0%, 6.0%, 11.0% pet.) were tested in 3418 consecutive dermatitis patients. Results: Ox. linalool 2.0%, 4.0%, 6.0%, and 11.0% pet. detected positive patch test reactions in 0.83%, 3.2%, 5.3%, and 7.2% of the tested patients, respectively. The doubtful reactions increased with rising concentrations but relatively less, giving 5.1%, 6.4%, and 7.3% doubtful reactions, respectively, for ox. linalool 4.0%, 6.0%, and 11.0% pet. Few irritative reactions were seen. Conclusions: Raising the patch test concentration for ox. linalool gave a better detection of contact allergy, as many as 5-7% positive patch test reactions were detected. We suggest a patch test concentration of ox. linalool 6.0% pet. for future patch testing, giving a dose per unit area of 2.4 mg/cm(2) when 20 mg test substance is tested in small Finn Chambers (R).
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