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| 2. |
- Viketoft, Maria
(author)
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Determinants of small-scale spatial patterns: Importance of space, plants and abiotics for soil nematodes
- 2013
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In: Soil Biology and Biochemistry. - : Elsevier BV. - 0038-0717 .- 1879-3428. ; 62, s. 92-98
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Journal article (peer-reviewed)abstract
- Belowground communities support a great diversity of organisms, but the factors that maintain and regulate this diversity are poorly understood. Both abiotic and biotic factors affect the abundance, diversity and distribution of soil organisms, and the spatial heterogeneity in these factors is a key in explaining belowground biodiversity. However, a combined approach estimating the relative importance of spatial and environmental factors in small-scale structuring of soil communities is yet missing. Here, a semi-natural grassland in south-central Sweden with high diversity of plants was sampled at two spatial scales (10 and 60 cm intervals) with the aim to examine the relative roles of plant identity, abiotic environmental factors and spatial factors for the small-scale spatial patterns of nematodes. The data were analysed by variance partitioning with redundancy analysis. Space, vegetation and abiotics were of similar importance for variation in nematode community composition. However, the contribution of the different sets of variables differed between the different nematode feeding groups: plant-feeding nematodes were influenced more by spatial variables, fungal-feeding nematodes and omnivores/predators more by plants and bacterial-feeding nematodes more by abiotic variables. The ranges of spatial dependence for the different feeding groups were all of the same magnitude, around 1 m. The results add to the understanding of the factors that contribute to soil biodiversity, and they show that combining plant and abiotic variables into one set of environmental variables hide important information about the drivers for belowground community assembly. (C) 2013 Elsevier Ltd. All rights reserved.
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| 3. |
- Viketoft, Maria
(author)
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Effects of plant species and plant diversity on soil nematodes - a field experiment on grassland run for seven years
- 2011
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In: Nematology. - 1388-5545 .- 1568-5411. ; 13, s. 115-131
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Journal article (peer-reviewed)abstract
- Plant species identity and diversity may greatly influence the composition of the nematode fauna. In this study the development of the nematode fauna was followed in a field experiment on arable soil with monocultures and mixtures of several plant species. Experimental plots were sown with one, four or 12 species of grass, legumes and forbs and were sampled four times in 7 years. Nematode diversity was little influenced by plant diversity. Due to a pronounced increase of Paratylenchus project us populations, the Shannon diversity index decreased in several treatments towards the end of the experiment. Differences in nematode faunal composition among treatments increased with time. In spite of the rather long duration of the experiment, the faunal composition did not stabilise but changed continuously. The obligate plant feeders Tylenchorhynchus dubius, T maximus and Pratylenchus spp. occurred in higher numbers in monocultures than in mixtures of several plant species. Among the microbivores, the abundance of some bacterial- and fungal-feeding nematode taxa seemed to be directly influenced by the plant species identity. In the plots with Trifolium spp. there was an increase of rapidly growing bacterial feeders belonging to Rhabditidae and Panagrolaimidae already after the first growing season. The abundances of some bacterial-feeding nematodes were correlated to total plant production. The numbers of the omnivorous Mesodorylaimus sp. appeared to be influenced by the degree of plant coverage. The abundance of several nematode taxa appeared to be little influenced by the composition of the vegetation. The plant feeder P. projectus and the bacterial feeder Prismatolaimus sp. reacted rather slowly and a distinct increase in numbers was only seen after 7 years, when P projectus strongly dominated the fauna in several treatments. Among the bacterial feeders, some species with moderate growth rate belonging to Cephalobidae decreased with time in several treatments.
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| 4. |
- Viketoft, Maria
(author)
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Soil and Freshwater and Marine Sediment Food Webs: Their Structure and Function
- 2013
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In: Bioscience. - : Oxford University Press (OUP). - 0006-3568 .- 1525-3244. ; 63, s. 35-42
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Journal article (peer-reviewed)abstract
- The food webs of terrestrial soils and of freshwater and marine sediments depend on adjacent aboveground or pelagic ecosystems for organic matter input that provides nutrients and energy. There are important similarities in the flow of organic matter through these food webs and how this flow feeds back to primary production. In both soils and sediments, trophic interactions occur in a cycle in which consumers stimulate nutrient cycling such that mineralized resources are made available to the primary producers. However, aquatic sediments and terrestrial soils differ greatly in the connectivity between the production and the consumption of organic matter. Terrestrial soils and shallow aquatic sediments can receive organic matter within hours of photosynthesis when roots leak carbon, whereas deep oceanic sediments receive organic matter possibly months after carbon assimilation by phytoplankton. This comparison has implications for the capacity of soils and sediments to affect the global carbon balance.
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| 5. |
- Viketoft, Maria
(author)
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Soil nematode populations in a grassland plant diversity experiment run for seven years
- 2011
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In: Applied Soil Ecology. - : Elsevier BV. - 0929-1393 .- 1873-0272. ; 48, s. 174-184
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Journal article (peer-reviewed)abstract
- Plant species identity and diversity may greatly influence the composition of the nematode fauna. The abundance of various nematode populations was investigated in a field experiment on plant diversity. 58 plots in an arable field planted with plant species growing alone or together up to a richness of 12 species were sampled after seven years for analysis of composition of the nematode fauna. Two additional control plots without vegetation were also sampled. Plant species identity was generally more important than plant diversity for the composition of the nematode fauna. Only the omnivorous Aporcelaimidae was positively related to plant species richness, and the fungal-feeding Aphelenchus and the bacterial-feeding Prismatolaimus were affected by functional diversity. Some nematode populations were strongly influenced by plant species composition, e.g. the plant-feeder Tylenchorhynchus maxim us was clearly coupled to the grass Phleum pratense. Nematode species within a feeding group sometimes had a rather specific abundance patterns under various plant species and plant species combinations. This was especially the case with the plant-feeding nematodes some of which obviously were directly influenced by the host suitability of specific plant species. Other nematode species were probably more influenced by indirect effects of plants on edaphic and nutrient conditions including biotic interactions from other components in the soil organism community. Yet other nematode species were little influenced by the kind of vegetation in the different plots. Our results show that to fully understand plant community effects on the nematode fauna there is a need to go further than just a division into nematode feeding groups. (C) 2011 Elsevier B.V. All rights reserved.
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| 6. |
- Viketoft, Maria, et al.
(author)
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Synergistic interaction between plant-feeding nematodes and the fungus rhizoctonia solani in potato
- 2014
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In: Journal of Nematology. - 0022-300X. ; 46, s. 252-253
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Conference paper (peer-reviewed)abstract
- Stem canker caused by the pathogenic fungus Rhizoctonia solani is a major problem for potato cultivation throughout Sweden, especially as it leads to great economic losses. Advisors and growers have developed a theory that there is a correlation between the severity of stem canker and plant-feeding nematodes, as high occurrences of stubby-root and rootlesion nematodes were found in potato fields with high incidence of stem canker. The aim of this project was to investigate any interactions between these nematodes and the fungus under controlled conditions. In the first experiment, pregerminated minitubers (cv King Edward) were planted in pots with sterilised sand and placed in a climate chamber at conditions corresponding to a Swedish spring. Fungal mycelium and/or nematodes (Pratylenchus penetrans) were added to the pots in various combinations. The pots were harvested ten weeks after inoculation and the parameters measured were fresh and dry weight of stems, stolons, tubers and roots, as well as the gradation of the damage caused by the nematodes and the fungus of the different plant parts. The nematodes produced feeding symptoms on stems, tubers, stolons and roots, but the roots also became brownish to different degrees. The fungus caused stem canker of different severity on the stems, burned off stolons and produced sclerotia on the roots and on the majority of the tubers. We found a synergistic effect between R. solani and P. penetrans, as the tuber yield decreased significantly when both nematodes and fungus were present in the pots.
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| 7. |
- Viketoft, Maria, et al.
(author)
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Temporal dynamics of soil nematode communities in a grassland plant diversity experiment
- 2011
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In: Soil Biology and Biochemistry. - : Elsevier BV. - 0038-0717 .- 1879-3428. ; 43, s. 1063-1070
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Journal article (peer-reviewed)abstract
- We report here on an 8-year study examining links between plant and nematode communities in a grassland plant diversity experiment, located in the north of Sweden on previous agricultural soil. The examined plots contained 1. 4 and 12 common grassland plant species from three functional groups: grasses, legumes and forbs. The same plant species composition was maintained in the plots through weeding and resowing during the experimental period. The hypotheses were (i) that the nematode community would shift towards a more diverse and mature fauna over time and (ii) that the effects of both plant species identity and plant species richness would increase over time. As hypothesized, the Bongers' Maturity Index (a measure of nematode responses to disturbance) increased over time, but not nematode diversity. Instead, the nematode community development in the present grassland experiment seemed to be more characterized by shifts in dominance patterns than by colonization of new taxa. Clear temporal trends were found for plant-feeders and Adenophorea bacterial-feeders which increased in abundance over time in almost all plant treatments. Rhabditidae bacterial-feeders decreased in abundance over time, in particular in plots with legumes. Fungal-feeders, omnivores/predators and the two nematode indices PPI (Bongers' Plant Parasitic Index) and NCR (Nematode Channel Ratio) had significant interactions between plant composition and time giving some support to our second hypothesis. Our results highlight the need for long-term experiments to examine plant species effects on soil fauna, especially on taxa belonging to higher trophic levels. The results also stress the importance of plant composition for belowground soil faunal communities. (C) 2011 Elsevier Ltd. All rights reserved.
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