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Digitale Medien

Interplay of omnivory, energy channels and C availability in a microbial-based soil food web (1999)

Mikola, J. ; Setälä, H.

Springer

Biology and fertility of soils 28 (1999), S. 212-218

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ISSN: 1432-0789

Schlagwort(e): Key words Omnivory ; Soil food web ; Energy channel ; Nematode ; Microbial production

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie , Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft

Notizen: Abstract To study the effects of omnivory on the structure and function of soil food webs and on the control of trophic-level biomasses in soil, two food webs were established in microcosms. The first one contained fungi, bacteria, a fungivorous nematode (Aphelenchoides saprophilus) and a bacterivorous nematode (Caenorhabditis elegans), and the second one fungi, bacteria, the fungivore and an omnivorous nematode (Mesodiplogaster sp.) feeding on both bacteria and the fungivore. Half of the replicates of each food web received additional glucose. The microcosms were sampled destructively at 5, 9, 13 and 19 weeks to estimate the biomass of microbes and nematodes and the soil NH4 +-N concentration. The evolution of CO2 was measured to assess microbial respiration. Microbial respiration was increased and soil NH4 +-N concentration decreased by the addition of glucose, whereas neither was affected by the food-web structure. Supplementary energy increased the biomass of fungi and the fungivore, but decreased the biomass of bacteria, the bacterivore and the omnivore. The omnivore achieved greater biomass than the bacterivore and reduced the bacterial biomass less than the bacterivore. The biomass of the fungivore was smaller in the presence of the omnivore than in the presence of the bacterivore at three sampling occasions. Fungal biomass was not affected by food-web structure. The results show that the effects of the omnivore were restricted to its resources, whereas more remote organisms and soil processes were not substantially influenced. The results also indicate that the presence of an omnivore does not necessarily alter the control of populations as compared with a food web containing distinct trophic levels, and that the fungal and bacterial channels may respond differently to changes in energy supply.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/s003740050485

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Digitale Medien

A microcosm study on the respiration and weight loss in birch litter and raw humus as influenced by soil fauna (1988)

Setälä, H. ; Haimi, J. ; Huhta, V.

Springer

Biology and fertility of soils 5 (1988), S. 282-287

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ISSN: 1432-0789

Schlagwort(e): Soil fauna ; Decomposition ; CO2 production ; Birch litter ; Raw humus ; Microcosm

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie , Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft

Notizen: Summary The effect of diverse soil fauna (Collembola, Acari, Enchytraeidae, Nematoda) on decomposition of dead organic matter was studied in microcosms containing (1) birch leaf litter, (2) raw humus of coniferous forest and (3) litter on humus. Total respiration (CO2 evolution) was monitored weekly, and mass loss, length of fungal hyphae (total and metabolically active) and survival of animal populations were checked at the end of weeks 12 and 21–22 from the start of experiment. Animal populations established themselves well during the incubation. At the end of the experiment some replicates containing litter had microarthropod densities of up to 500 specimens per microcosm, corresponding to a field population of 200 000 m−2. The soil animals had a positive influence on total respiration in all substrates. By the end of experiment 32.0%, 22.6% and 14.6% more CO2 had evolved in the presence of animals in litter, litter + humus and humus alone, respectively. There was clear trend towards a higher mass loss in the presence of animals, though it was significant in litter only. Our results showed that a diverse soil animal community enhances the activity of soil microbes, and may thereby accelerate decomposition in raw coniferous forest soil.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00262132

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Digitale Medien

Enclosing decomposer food web: implications for community structure and function (1997)

Nieminen, J. K. ; Setälä, H.

Springer

Biology and fertility of soils 26 (1997), S. 50-57

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ISSN: 1432-0789

Schlagwort(e): Key words Decomposer food web ; Dispersion ; Isolation ; Litter-bags ; Spatial scale

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie , Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft

Notizen: Abstract We designed a field experiment to evaluate how restriction of soil faunal movements affects decomposer community structure, food web architecture, and decomposition of organic matter. Intact soil cores (3cm thick, diameter 16cm) were placed either in “open” (mesh size 1mm, allowing all meso- and microfauna to move through) or “closed” (27μm, animal movement prevented except for the smallest microfauna) mesh bags in early May. Before being buried in the forest floor of a mixed spruce stand, hay litter was placed in the mesh bags in separate litter bags. The samplings took place 2 and 6 months after establishing the experiment. Additional “field samples” were taken from the adjacent soil to determine possible side effects of the mesh-bags. Physicochemical conditions, decomposition rate of hay litter, and total respiration of soil cores were identical in the two bag treatments. Enchytraeids increased significantly in the closed treatment, while macrofauna, such Coleoptera larvae and dipteran larvae, went close to extinction in the closed bags. The elevated enchytraeid number is in accordance with the findings of closed microcosm studies, and is best explained by reduced predation by macrofauna. Although a set of 14 mite taxa was found to distinctively reflect the degree of isolation, neither the total number of individuals nor the number of microarthropod taxa differed between the bag treatments, or between the bags and the field samples. It is concluded that in the time-span of one growing season, reduction in the spatial scale does not necessarily reduce the diversity of fauna but can significantly change the decomposer food-web architecture.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/s003740050342

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