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- Bååth, Erland, et al.
(författare)
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Effect of nitrogen and carbon supply on the development of soil organism populations and pine seedlings - microcosm experiment
- 1978
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Ingår i: Oikos. - 1600-0706. ; 31:2, s. 153-163
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Tidskriftsartikel (refereegranskat)abstract
- Series of pots containing Scots pine seedlings and a humus-sand mixture were watered twice weekly for 398 d with different nutrient solutions (control treatment with complete plant nutrient solution less nitrogen; glucose addition; nitrogen addition; glucose and nitrogen addition). Analyses were made of organic and nitrogen contents in the substrate, plant weights and nitrogen contents, nitrogen fixation and respiration rates, abundance, biomass and in some cases species composition of different soil organism populations. The growth rate of pine seedlings was lowest in series supplied with glucose, which is most easily explained by a deficiency of nitrogen due to microbial immobilization. The fungi and yeast were stimulated by addition of an easily available carbon source whereas the bacteria needed both nitrogen and carbon to maintain high biomass. A positive correlation between fungal feeding soil organisms and amount of fungal mycelium was found while a more complex situation prevailed with regard to bacterial numbers and bacterial feeding nematodes. The systems are evaluated in relation to the different treatments and compared with the field situation.
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- 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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