| 1. |
- Mäki, Mari, et al.
(författare)
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Heterotrophic and rhizospheric respiration in coniferous forest soils along a latitudinal gradient
- 2022
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Ingår i: Agricultural and Forest Meteorology. - : Elsevier BV. - 1873-2240 .- 0168-1923. ; 317
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Tidskriftsartikel (refereegranskat)abstract
- Northern forest soils are a major carbon (C) reservoir of global importance. To estimate how the C balance in these soils will change, the roles of tree roots and soil microbes in C balance should first be decoupled. This study determined how the activity of heterotrophs and tree roots together with root-associated microbes in the rhizosphere varies in coniferous forest soils in boreal, hemiboreal, and temperate climates along a latitudinal gradient using a trenching approach. We created experimental plots without living tree roots, measured soil respiration (CO2 efflux) from these and from unmanipulated plots using the chamber technique, and partitioned the efflux into root-rhizosphere (RR) and heterotrophic (RH) respiration. The share of RR in ecosystem gross primary production (GPP) decreased from north to south in the Scots pine (Pinus sylvestris L.) and the Norway spruce (Picea abies (L.) Karst.) forests, with the exception of a mixed site, where the share of RR in GPP varied strongly between the years. RR per ground area and per root biomass were mainly independent of climate within the gradient. RH per ground area increased from north to south with temperature, while RH per soil C did not change with temperature. Soil moisture did not significantly affect the respiration components in the northernmost site, whereas soil moisture was positively connected with RH and negatively with RR in other Scots pine sites and positively connected with RR in pure Norway spruce stands. The dynamic ecosystem model LPJ-GUESS was able to capture the seasonal dynamics of RH and RR at the sites, but overall accuracy varied markedly between the sites, as the model underestimated RH in the southern site and RR elsewhere. Our study provides knowledge about the nature of soil respiration components. The valuable insights can be used in more accurate land-ecosystem modelling of forest ecosystems.
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| 2. |
- Nordin, Lisa, 1981-, et al.
(författare)
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Analysis of the quality of optical fibre and fines measurement for prediction of dewatering characteristics for mechanical pulps
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The quality of the optical fibre and fines measurement has been investigated. Fibres and fines of different quality were mixed in defined proportions and the mixtures were characterized by means of optical fibre measurements and dewatering behaviour. The results show that the same measured fines amounts show different dewatering behaviour, depending on the quality of the fines used. The difference in fines quality was, however, not reflected in the optical measurement. We conclude that this is caused by too low resolution in the optical measurement, so there is a large need for higher resolution of the measurement equipments in order to make it possible to measure the shape of the fines.
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| 3. |
- Nordin, Lisa, 1981-, et al.
(författare)
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Measurement and prediction of dewatering characteristics for mechanical pulps using optical fibre analyzers
- 2009
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Ingår i: Proceedings - 2009 International Mechanical Pulping Conference, IMPC 2009. ; , s. 309-316
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Konferensbidrag (refereegranskat)abstract
- The aim of this work was to obtain an on-line measurement for dewatering behaviour in the wire section based on fibre and fines characteristics. Four laboratory dewatering equipments were compared and the fibre characteristics were measured by means of optical fibre analyzers. The results show that rough correlations do appear to exist between the dewatering equipments; however they rank the pulps differently depending on the raw wood material used and whether the refining conditions are mild or harsh. The prediction models based on fibre characteristics showed a high degree of statistical accuracy. The descriptions, however, proved not to be sufficiently good with regards to the dewatering behaviour for them to be used in relation to on-line applications. This might have been because consideration was not given to some important variables which do, in fact, have a significant impact on the drainability. These variables could include physical fibre properties or others that are not measured, or properties that, at present, are unable to be measured at a sufficient resolution.
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| 4. |
- Norén, Torbjörn, 1955-
(författare)
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Clostridium difficile : epidemiology and antibiotic resistance
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Clostridium difficile is a spore-forming toxin-producing intestinal bacterium abundant in soils and waters. This pathogen relies on increased growth by a disturbed intestinal microflora and the production of two cytotoxins, toxin A and toxin B, which may cause anything from mild self-limiting C. difficile associated diarrhea (CDAD) to severe and fatal pseudomembranous colitis (PMC). Typically CDAD following antibiotic therapy is due either to overgrowth of endogenous C. difficile or through spores transmitted from the environment. The hospital setting provides frequent antibiotic use and the source of numerous infective spores from CDAD patients, the environment or nursing staff. Today we experience a 10-fold increase of incidence in the US and Canada (1991-2003) apparently due to a current epidemic C. difficile strain (NAP1/027). Current incidence from Canada is estimated to 156/100 000 compared to 50/100 000 in Sweden 1995. In the following thesis, investigations of CDAD in Örebro County in central Sweden resulted in the discovery an epidemic nosocomial C. difficile strain (SE17, serogroup C), found to be clindamycin-resistant. The majority of the isolates carried a gene (ermB) related to this resitance. We found an overall incidence during 1999-2000 of 97/100 000 or, if including recurrent episodes, 135/100 000 i.e. more than 100% increase since 1995. The incidence among hospitalized individuals was 1300-fold that in the community and 78% of episodes were classified as hospital-associated. This reflects a 37-fold difference in antibiotic consumption, as well as the predominance of the resistant SE17 hospital-associated strain (22% of hospital isolates compared to 6% of community isolates, p=0.008). Only 10% of the recurrent cases were found to be reinfections indicating that CDAD is mainly caused by endogenous strains and not by hospital transmission. Recent reports on failure of standard metronidazole therapy urge for alternative treatment agents and fusidic acid has been proven as effective in the treatment of CDAD. We could verify this, but in both treatment groups we found that persistence of C. difficile isolates post-treatment related to an increased risk of recurrent CDAD compared to the patients who were culture negative at follow-up (p=0.03). Most importantly, 55% of patients with follow-up isolates and who had been treated with fusidic acid, the strains had developed fusidic acid resistance. The corresponding pre-treatment identity of isolate genotype indicated selection of mutants. Relating to the known fusA resistance mechanism in Staphylococcus aureus we used the published sequence for this gene in Clostridium perfringens and found homologous fusA in the sequence of the referent strain C. difficile 630. Comparing fusA of the resistant mutants with the initial wild-type isolates, we identified novel mutations in fusA as the genetic key to fusidic acid resistance in C. difficile.
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| 5. |
- Nygren, Olle, et al.
(författare)
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On characterization of mechanical and chemimechanical pulps
- 2003
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Ingår i: International Mechanical Pulping conference, Quebec, Que, Canada, 2-5 June 2003. - Montreal : Pulp and Paper Technical Association of Canada. - 1896742866 ; , s. 486-
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Konferensbidrag (refereegranskat)
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