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- Bäckman, Jenny, 1974-, et al.
(författare)
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Clear-cutting affects the ammonia-oxidising community differently in limed and non-limed coniferous forest soils
- 2004
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Ingår i: Biology and Fertility of Soils. - : Springer Science and Business Media LLC. - 0178-2762 .- 1432-0789. ; 40:4, s. 260-267
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Tidskriftsartikel (refereegranskat)abstract
- The effects of clear-cutting on the ammonia-oxidising bacterial community were studied in the soil of limed and non-limed spruce forest plots located in the central part of southern Sweden. The communities were studied using denaturing gradient gel electrophoresis (DGGE) profiling after polymerase chain reaction (PCR) amplification from total DNA with primers reported to be specific for beta-subgroup ammonia-oxidising bacteria. The bands on the DGGE were sequenced and each unique sequence was interpreted as representing one ammonia-oxidising population. The relative abundance of each population was determined by measuring the fluorescence of the respective DGGE bands. In both limed and non-limed soil, the same two Nitrosospira populations were found, one belonging to cluster 2 (NScl2) and one to cluster 4 (NScl4). However, while NScl4 first appeared a year after the clear-cutting in the non-limed plot, it was present both before and after the cutting in the limed plot. Irrespective of previous liming, clear-cutting caused a shift in the ammonia-oxidiser community, from dominance by the NScl2 population to a community with approximately equal relative abundance of NScl2 and NScl4. In both plots the total size of the community increased after clear-cutting (based on increased DGGE band intensity), most likely due to increased NH4+ availability, but the growth response was faster in the limed plot. Hence, the prior liming increased the responsiveness of the ammonia-oxidisers to the changes caused by cutting. This is the first study to report the effects of clear-cutting on the ammonia-oxidising community, and the results show a clear correlation between increased potential nitrification and a shift in the ammonia-oxidiser community.
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| 2. |
- Johansson, Elisabeth, et al.
(författare)
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Nitrous oxide exchanges with the atmosphere of a constructed wetland treating wastewater - Parameters and implications for emission factors
- 2003
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Ingår i: Tellus Series B-Chemical and Physical Meteorology. - : Stockholm University Press. - 0280-6509 .- 1600-0889. ; 55:3, s. 737-750
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Tidskriftsartikel (refereegranskat)abstract
- Static chamber measurements of N2O fluxes were taken during the 1998 and 1999 growth seasons in a Swedish constructed wetland receiving wastewater. The dominating plant species in different parts of the wetland were Lemna minor L., Typha latifolia L., Spirogyra sp. and Glyceria maxima (Hartm.) and Phalaris arundinacea (L.), respectively. There were large temporal and spatial variations in N2O fluxes, which ranged from consumption at -350 to emissions at 1791 mug N2O m(-2) h(-1). The largest positive flux occurred in October 1999 and the lowest in the middle of July 1999. The average N2O flux for the two years was 130 mug N2O m(-2) h(-1) (SD = 220). No significant differences in N2O fluxes were found between the years, even though the two growing seasons differed considerably with respect to both air temperature and precipitation. 15% of the fluxes were negative, showing a consumption of N2O. Consumption occurred on a few occasions at most measurement sites and ranged from 1-350 mug N2O m(-2) h(-1). 13-43% of the variation in N2O fluxes was explained by multiple linear regression analysis including principal components. Emission factors were calculated according to IPCC methods from the N2O fluxes in the constructed wetland. The calculated emission factors were always lower (0.02-0.27%) compared to the default factor provided by the IPCC (0.75%). Thus, direct application of the IPCC default factor may lead to overestimation of N2O fluxes from constructed wastewater-treating wetlands.
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