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| 2. |
- Bååth, Erland, et al.
(författare)
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Impact of microbial-feeding animals on total soil activity and nitrogen dynamics - a soil microcosm experiment
- 1981
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Ingår i: Oikos. - 1600-0706. ; 37:3, s. 257-264
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Tidskriftsartikel (refereegranskat)abstract
- Abstract in UndeterminedThe long-term impact of microbial-feeding animals on microbial populations was studied in microcosms containing pine seedlings growing in a gamma sterilized humus-sand mixture. Organism communities of diverse complexity were introduced into the microcosms. The two main experimental series contained microorganisms only and microorganisms and microorganism-feeding nematodes, respectively. After 18 months the following analyses were made: soil chemical characteristics, weight and nitrogen content of the seedlings, soil respiration, abundance, biomass, and in some cases, species composition of the different soil organism populations. During the incubation, leaching of nitrogen from the microcosms was measured continuously. The rate of nitrogen leaching from the microcosms increased during the first 6 months. During the remaining 12 months the leaching stabilized at a low rate. Initially, the series with microbial-feeding nematodes had a lower rate of nitrogen loss through leaching compared to the series with only microorganisms added. Towards the end of the experiment the situation was reversed. The pine seedlings showed a very poor growth in all series with no significant differences between the treatments. In the microcosms, bacteria appeared to be the most important microorganism group; fungi, algae and yeasts were present in low amounts. The presence of bacterial feeding nematodes reduced the number of bacteria but did not reduce the soil respiration rate. A significant correlation was obtained between the numbers of nematodes and the respiration rate of the microcosms, which is interpreted as an increased bacterial production rate due to the presence of bacterial-feeding animals.
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| 3. |
- Clarholm, M., et al.
(författare)
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Biological aspects of nitrogen mineralization in humus from a pine forest podsol incubated under different moisture and temperature conditions
- 1981
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Ingår i: Oikos. - 1600-0706. ; 37:2, s. 137-145
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Tidskriftsartikel (refereegranskat)abstract
- Abstract in UndeterminedFluctuations of soil organism abundance, soil respiration and inorganic nitrogen werestudied in a laboratory experiment on material taken from the humus layer of a Scotspine forest and incubated under different moisture and temperature regimes. Theexperiment was run for 28 wk with samplings every 7 wk. At 28 wk, increases in"total movable N" (inorganic N + biomass N) were observed in samples incubated athigh temperature and/or high moisture content. Most of the N was found in biomassexcept in incubations at the highest temperatures and moistures. Under those conditions,high abundance of nematodes occurred together with drastically increasedamounts of inorganic N. Low values of inorganic N were recorded under conditionscommon in the field. No obvious relations could be detected between standing cropsof bacteria and temperature, moisture or respiration. The number of bacterial-feedingnematodes seemed to be a possible measure of previous bacterial productioncontributing more information than the standing crop measurements of the bacteria,which varied little despite the direct evidence of substantial bacterial production insome incubation conditions.
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| 4. |
- Blomquist, Göran K., et al.
(författare)
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Separation of fungal propagules by partition in aqueous polymer 2-phase systems
- 1984
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Ingår i: Applied and Environmental Microbiology. - 0099-2240. ; 47:6, s. 1316-1318
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Tidskriftsartikel (refereegranskat)abstract
- Conidia of Penicillium chrysogenum and Penicillium frequentans and sporangiospores of Rhizopus rhizopodiformis, Rhizomucor pusillus, and Mucor racemosus were subjected to partition in aqueous polymer two-phase systems. The partition behavior differed drastically between the conidia of the two Penicillium species and the sporangiospores of the three species of phycomycetes. This difference in partition behavior can be used for purification of fungi belonging to different taxonomical groups. P. frequentans was completely separated from M. racemosus by two extractions, whereas four extractions were needed to purify M. racemosus. This method was used on an air sample from a locality where wood fuel chips are handled. The conidia of the fungi Trichoderma viride and Rhizopus rhizopodiformis were removed completely by only two extractions.
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| 5. |
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| 6. |
- Bååth, Erland, et al.
(författare)
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Fungal populations in podzolic soil experimentally acidified to simulate acid-rain
- 1984
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Ingår i: Microbial Ecology. - 1432-184X. ; 10:3, s. 197-203
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Tidskriftsartikel (refereegranskat)abstract
- Abstract in UndeterminedThe effect of experimental acidification on the soil microfungalcommunity was studied in the humus layer of a coniferous forest in northern Sweden. The study was made 4 years after the last application of sulfuric acid. Fungal species composition was altered by treatments of 100 and 150 kg sulfuric acid ha-1 each year for 6 years, yet no differences were found between the control treatment and an application of 50 kg ha-1. The abundance of Penicillium spinulosum and Oidiodendron cf. echinulatum II increased with increasing rates of acid application, whereas only small changes were found for other isolated fungal taxa. Soil respiration rate and fluorescein diacetate (FDA)-active fungal biomass were significantly different from the control treatment at all 3 levels of acidification.
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| 7. |
- Lundgren, B., et al.
(författare)
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Bacterial numbers in a pine forest soil in relation to environmental-factors
- 1983
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Ingår i: Soil Biology & Biochemistry. - : Elsevier BV. - 0038-0717. ; 15:6, s. 625-630
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Tidskriftsartikel (refereegranskat)abstract
- Abstract in Undetermined Numbers of soil bacteria stained with acridine orange (AO) or fluorescein diacetate (FDA) were studied for 3 and 2 yr respectively. Three pine forest sites were used and both organic and mineral soil layers were included. Different patterns of fluctuation in bacterial numbers were found each year. Significant correlations were demonstrated between AO-stained bacterial numbers and soil moisture content and between FDA-stained bacteria and the accumulated precipitation during a week before the sampling date. In multiple regression analyses 60–80% of the variation in numbers of AO-stained bacteria could be accounted for by soil moisture and numbers of bacterial-feeding nematodes at the sampling dates, and 30–45% of the variation in numbers of FDA-stained bacteria was accounted for by precipitation.
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| 8. |
- Olsson, S., et al.
(författare)
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A fast and simple method for classification of soil bacterial-populations
- 1984
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Ingår i: Zeitschrift für Pflanzenernährung und Bodenkunde. - : Wiley. - 0044-3263. ; 147:2, s. 198-202
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Tidskriftsartikel (refereegranskat)abstract
- A simple method is described for a rough classification of soil bacterial populations. The method makes use of a commercially available biochemical test system and the test results are analysed in a multivariate classification program on a microcomputer. The method was used for classification of bacteria from rape rhizosphere.
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| 9. |
- Söderström, Bengt, et al.
(författare)
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Decrease in soil microbial activity and biomasses owing to nitrogen amendments
- 1983
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Ingår i: Canadian Journal of Microbiology. - 0008-4166. ; 29:11, s. 1500-1506
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Tidskriftsartikel (refereegranskat)abstract
- Microbial biomass and soil respiration rate decreased after application of 150 kg NH4NO3–N∙ha−1 to different coniferous forest podzols. The decrease was already found 3 months after fertilization and was still evident after 3–5 years. Changes in pH, organic matter, or water content in the soils could not explain the decreases. In laboratory experiments, several unfertilized forest soils were treated with 2 mg of NH4NO3–N or of urea–nitrogen∙g wet soil−1. The ammonium nitrate addition resulted in severe depressions of the respiration rates during and up to 175 days of incubation and the decrease was evident after about 1 week. The urea treatment initially increased the respiration rate of the soils, but this appeared to be a transitory effect.
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