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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Biology and fertility of soils 10 (1990), S. 163-169 
    ISSN: 1432-0789
    Keywords: Soil fauna ; Decomposition ; Raw humus ; Forest soil ; Microcosm ; CO2 evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Long-term experiments (ca. 2 years) were carried out in laboratory systems that simulated the complexity of a coniferous forest floor. The test materials were partially sterilized by freezing and thawing, and reinoculated with (1) microbes alone or (2) microbes with fauna. Removable microcosms containing birch litter, spruce litter, or humus were inserted into a humus substrate. Two experiments used organic matter only, and another included a layer of mineral soil below the humus. Both were incubated in climate chambers that simulated both summer and winter conditions. The evolution of CO2 was measured at regular intervals. In order to determine the C content of the leachates, the macrocosms and the microcosms were watered periodically. Soil fauna significantly increased respiration in the litter, but not in the microcosms containing humus. In the later phases of decomposition the presence of fauna had a negative effect. In the total systems the fauna consistently increased the respiration rate. The loss of mass was greater in the presence of fauna, especially during the middle phases (5–11 months), but it was higher in the controls later. Throughout the whole incubation period the decomposition rate was strongly influenced by the composition of the animal community. The interpretation of the results is affected by the fact that the controls, to which no fauna had been added, contained dense populations of microbial feeders (nematodes, rotifers, and protozoans).
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  • 2
    ISSN: 1432-0789
    Keywords: Soil fauna ; Raw humus ; Forest soil ; Mineralization ; Nutrient leaching ; Microcosm
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Long-term experiments (97–98 weeks) were carried out in macrocosm systems simulating the complexity of coniferous forest soil. The macrocosms were partially sterilized by freezing, thawing and drying, then re-inoculated with microbes alone or microbes + soil fauna. Removable microcosms containing birch litter, spruce litter, or humus were inserted into the substrate humus in the macrocosms. Two experiments used organic matter only, and in the third there was mineral soil below the humus. The macrocosms were incubated in climate chambers that simulated both summer and winter conditions. At 4- to 6-week intervals the substrates were irrigated for analyses of pH, total N, NH 4 + −N, NO 3 − −N, and PO 4 3− −P in the leachates. At the end of each growing season a destructive sampling was performed, including analyses of KCl-extractable N and P. Leaching of NH 4 + and PO 4 3− from both the litter and the total systems was significantly enhanced by the soil fauna. There were also differences in mineralization of N and P between the refaunated systems, apparently due to divergent development of the faunal communities. In general, fauna affected KCl-extractable nutrients from the litter positively, although this effect was less evident than in the leaching water. In the humus and mineral soil the fauna significantly increased the release of N and P, especially in the later stages of the experiments. Soil pH was higher in the presence of fauna, but there was no difference in the pH of the leachates. Not only invertebrate-microbial interactions, but also mutual relationships among fauna were important in the nutrient dynamics.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Biology and fertility of soils 28 (1999), S. 212-218 
    ISSN: 1432-0789
    Keywords: Key words Omnivory ; Soil food web ; Energy channel ; Nematode ; Microbial production
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: 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.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Biology and fertility of soils 26 (1997), S. 50-57 
    ISSN: 1432-0789
    Keywords: Key words Decomposer food web ; Dispersion ; Isolation ; Litter-bags ; Spatial scale
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: 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.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Biology and fertility of soils 5 (1988), S. 282-287 
    ISSN: 1432-0789
    Keywords: Soil fauna ; Decomposition ; CO2 production ; Birch litter ; Raw humus ; Microcosm
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: 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.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford [u.a.] : International Union of Crystallography (IUCr)
    Acta crystallographica 50 (1994), S. 1823-1825 
    ISSN: 1600-5759
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Biology and fertility of soils 10 (1990), S. 155-162 
    ISSN: 1432-0789
    Keywords: Microcosm ; Soil fauna ; Raw humus ; Forest soil ; Soil processes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary We developed a technique for simulating the complexity of the soil system under controlled laboratory conditions. Removable microcosms were inserted in a homogeneous substrate soil in a large plastic box. This macrocosm was sealed, except for an inlet and outlet for air flow, and an aperture for collecting leachates. The system can be designed and manipulated in various ways according to the needs of a particular experiment. Respiration and nutrient fluxes can be measured either from the whole macrocosm or separately from the microcosms. We have performed three experiments in order to evaluate the role of animals in the soil processes. A set of macrocosms was constructed from components of coniferous forest soil. These were partially sterilized by freezing and then thawing, and re-inoculated with (1) microbes alone, or (2) microbes and fauna. The animal populations became well established, average densities per area approaching those in natural forest soils. However, there were considerable differences in community structure between the experiments. The sterilization did not eliminate microfauna; nematodes reproduced to high densities in the control macrocosms.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1432-1939
    Keywords: Nuphar lutea ; Galerucella nymphaeae ; Herbivory ; Nitrogen dynamics ; Small aquatic systems
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The grazing effects of the waterlily beetle Galerucella nymphaeae on Nuphar lutea stands were studied in three ponds in Central Finland. Production of floating leaves of N. lutea and growth in the G. nymphaeae population were investigated in the ponds and bioenergetics of the beetle larvae in the laboratory. Combination of field and laboratory data enabled estimation of the effect of the beetle on the production of floating leaves of N. lutea and the consequences of grazing for the input of detritus from Nuphar into the ponds. Adults and larvae of G. nymphaeae consumed 3.0–6.1% of the net annual floating leaf production during the growing period. In addition to consumption losses, feeding accelerated the degradation rate of the leaves. This was associated with an increased flow of detrital material of Nuphar origin, and also with increased production of floating leaves in the ponds. These increments were estimated to be up to 3 times greater in the presence of grazing than without it. Grazing by G. nymphaeae releases substantial amounts of carbon and nitrogen bound in Nuphar, particularly in ponds with a dense Nuphar vegetation. It is hypothesized that feeding by this beetle may markedly affect the structure and functioning of such small aquatic systems.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Oecologia 125 (2000), S. 109-118 
    ISSN: 1432-1939
    Keywords: Key words  Cognettia sphagnetorum ; Mycorrhiza ; Nutrient cycling ; Pine rhizosphere ; Soil food web
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Mycorrhizal plants are commonly believed to direct much more of their photosynthates into the soil than non-mycorrhizal plants. As the growth of most organisms of the detrital food web is limited by energy, the flow of C through mycorrhizal plants into the below-ground milieu is widely assumed to nourish a variety of decomposer organisms in soils. In the current experiment, I explored whether some representatives of soil mesofauna, either fungivores or microbi-detritivores, derive benefit from the presence of ectomycorrhizal (EM) fungi growing on the roots of Scots pine (Pinus sylvestris). I also investigated whether the role of soil mesofauna in affecting pine growth depends on the presence of EM fungi in the pine rhizosphere. The study was established in microcosms with a mixture of raw humus and sand. The soil was defaunated, reinoculated with 10 species of soil bacteria and 11 species of saprophytic soil fungi, and pine seedlings, either infected or non-infected with four taxa of EM fungi, were planted in the microcosms. Five treatments with different food web configurations were established: (1) saprophytic microbes alone, (2) as (1) but with the omnivorous enchytraeid species Cognettia sphagnetorum present, (3) as (1) but with Collembola (Hypogastrura assimilis), (4) as (1) but with four species of oribatid mites (Acari) involved, and (5) as 1) but with C. sphagnetorum, H. assimilis and the Acari. The microcosms were incubated in a climate chamber with varying temperature and illumination regimes for two growing periods for the pine. After 60 weeks, pine biomass production was significantly greater in the mycorrhizal systems, the total biomass being 1.43 times higher in the presence than absence of EM fungi. Similarly, almost ten times more fungal biomass was detected on pine roots growing in the mycorrhizal than in the non-mycorrhizal systems. The presence of EM fungi was also associated with significantly lowered pH and percent organic matter of the soil. Despite the clearly larger biomass of both the pines and the fungi on the pine roots, neither the numbers nor biomasses of the mesofauna differed significantly between the EM and non-EM systems. The presence of Collembola and C. sphagnetorum had a positive influence on pine growth, particularly in the absence of EM fungi, whereas oribatid mites had no effects on pine growth. The complexity of the mesofaunal community was not related to the biomass production of the pines in a straightforward manner; for example, the complex systems with each faunal group present did not produce more pine biomass than the simple systems where C. sphagnetorum existed alone. The results of this experiment suggest that the short-term role of EM fungi in fuelling the detrital food web is less significant than generally considered, but that their role as active decomposers and/or stimulators of the activity of saprophytic microbes can be more important than is often believed.
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  • 10
    Publication Date: 2018-03-01
    Print ISSN: 0038-0717
    Electronic ISSN: 1879-3428
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Elsevier
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