| 1. |
|
|
| 2. |
|
|
| 3. |
|
|
| 4. |
- Lundström, Ulla, et al.
(author)
-
Advances in understanding the podzolization process resulting from a multidisciplinary study of three coniferous forest soils in the Nordic Countries
- 2000
-
In: Geoderma. - 0016-7061 .- 1872-6259. ; 94:04-feb, s. 335-353
-
Journal article (peer-reviewed)abstract
- Geochemical, mineralogical, micromorphological, microbiological, hydrochemical and hpdrological joint investigations were performed at two coniferous podzolic sites in the north of Sweden and at one in the south of Finland. Mycorrhizal fungi were found to create numerous pens (3-10-mu m diameter) in many weatherable mineral grains in the eluvial (E) horizon. During the growing season, identified low molecular weight (LMW) organic acids such as citric, shikimic, oxalic and fumaric acids comprised 0.5-5% of the DOC and 0.5-15% of the total acidity in soil solutions. Between 20% and 40% of the dissolved Al was bound to the identified LMW organic acids. Mineral dissolution via complexing LMW acids, probably exuded in part by the mycorrhiza hyphae, is likely to be a major weathering process in podzols. We found no evidence for a decreasing C/metal ratio of the migrating organo-metal complexes that could explain the precipitation of secondary Fe and AL in the illuvial (B) horizon. Instead, microbial degradation of organic ligands resulting in the release of ionic,Al and Fe to the soil solution may he an important process facilitating the formation of solid Al-SI-OH and Fe-OH phases in the podzol B horizon. However, within the B horizon transport as proto-imogilite (PI) sols might be possible. In the B horizon, the extractable,Al and Fe was predominantly inorganic. The large specific surface area (SSA) removable by oxalate extraction, the high point of zero charge salt effect (PZSE), the low cation exchange capacity (CEC) and the high sulphate exchange capacity (SEC), painted to the presence of short-range ordered variable charge phases. Imogolite type material (ITM) was indeed identified in all B horizons by IR spectroscopy and crystalline imogolite was found in the deep B horizon of one profile. Mossbauer spectroscopy indicated that Fe in the form of ferrihydrite was formed by intergrowth with an Al-Si-OH phase. The high amounts of Fe and Al transported from the O to the E horizon indicate that there could be an upward transport of these elements before they are leached to the B horizon. We hypothesize that the LMW Al complexes an transported by hyphae to the mor (O) layer, partly released and subsequently complexed by high molecular weight (HMW) acids.
|
|
| 5. |
|
|
| 6. |
|
|
| 7. |
|
|
| 8. |
|
|
| 9. |
|
|
| 10. |
|
|
| 11. |
|
|
| 12. |
|
|
| 13. |
|
|
| 14. |
|
|
| 15. |
|
|
| 16. |
|
|
| 17. |
|
|
| 18. |
- Riise, G., et al.
(author)
-
Mobility of different size fractions of organic carbon, Al, Fe, Mn and Si in podzols
- 2000
-
In: Geoderma. - 0016-7061. ; 94:2-4, s. 237-247
-
Journal article (peer-reviewed)abstract
- The influence of size distribution on the translocation of organic carbon, Fe, Al, Mn and Si in soil waters, has been studied in Scandinavian podzol profiles from three different locations. Soil solutions from different horizons have been filtered through a 0.45 μm membrane filter prior to further size fractionation by ultramembrane techniques. Organic carbon, Fe, Al, Mn and Si were determined in: (I) a colloidal fraction-nominal molecular weight cutoff > 3 kDa, (II) a medium size fraction-nominal molecular weight cutoff 1-3 kDa, and (III) a low molecular size fraction-nominal molecular weight cutoff < 1 kDa. The colloidal fraction comprise large proportions of organic carbon in the O and the E horizons, while low molecular size organic carbon fractions increase with depth in the B horizon on a percentage basis. A major part of Fe and Al seems to be associated with the colloidal fraction of organic carbon in the O horizon, and results suggest that colloidal organic matter contribute to the vertical translocation of metals through the E horizon. Maximum concentrations of Si, Al and Fe are found in the E horizon. Concentration of colloidal Si is significantly higher in the E than the other horizons. Although the total concentration of Si is four times the concentration of Al, colloidal Si and Al are present in more or less similar concentrations. This suggest that Si and Al are associated with each other in colloids in the E horizon. Equilibrium calculations, however, indicate that proto-imogolite sols are not very likely, and correlation coefficients rather suggest interaction of Al with colloidal organic carbon. The major part of Fe is in the colloidal fraction in all horizons. In contrast, Mn decreases sharply with depth, and is generally in a low molecular weight form. This indicates that Mn is related to the litter turnover process and that Mn takes little part in the podzolization process.
|
|
| 19. |
|
|
| 20. |
- Strand, John A., et al.
(author)
-
Dynamics of submerged macrophyte populations in response to biomanipulation
- 2001
-
In: Freshwater Biology. - Chichester, United Kingdom : Wiley-Blackwell. - 0046-5070 .- 1365-2427. ; 46:10, s. 1397-1408
-
Journal article (peer-reviewed)abstract
- 1. A 6-year study (1992-97) of changes in submerged vegetation after biomanipulation was carried out in the eutrophicated Lake Finjasjon, Southern Sweden. Ten sites around the lake were revisited each year. At each site five samples of above-ground biomass were taken at 10 cm water depth intervals. An investigation of the seed bank at the 10 sites, and a grazing experiment where birds and large fish were excluded was also conducted. 2. Between 1992 and 1996, in shallow areas (water depth < 3 m), vegetation cover 2 increased from < 3 to 75% and above-ground biomass from < 1 to 100 g DW m(-2). Mean outer water depth increased from 0.3 to 2.5 m. Elodea canadensis and Myriophyllum spicatum accounted for > 95% of the increase in biomass and plant cover. The following year (1997), however, cover and above-ground biomass decreased, mainly attributable to the total disappearance of E. canadensis. Secchi depth increased after biomanipulation until 1996, but decreased again in 1997. 3. Total and mean number of submerged species increased after biomanipulation, probably as a result of the improved light climate. However, after the initial increase in species number there was a decrease during the following years, possibly attributed to competition from the rapidly expanding E. canadensis and M. spicatum. The lack of increase in species number after the disappearance of E. canadensis in 1997 implies that other factors also affected species richness. 4. A viable seed bank was not necessary for a rapid recolonization of submerged macrophytes, nor did grazing by waterfowl or fish delay the re-colonization of submerged macrophytes. 5. Submerged macrophytes are capable of rapid recolonization if conditions improve, even in large lakes such as Finjasjon (11 km(2)). Species that spread by fragments will increase rapidly and probably outcompete other species. 6. The results indicate that after the initial Secchi depth increase, probably caused by high zooplankton densities, submerged vegetation further improved the light climate. The decrease in macrophyte biomass in 1997 may have caused the observed increase in phosphorus and chlorophyll a, and the decrease in Secchi depth. We suggest that nutrient competition from periphyton, attached to the macrophytes, may be an important factor in limiting phytoplankton production, although other factors (e.g. zooplankton grazing) are also of importance, especially as triggers for the shift to a clear-water state.
|
|
| 21. |
- Strand, John A., et al.
(author)
-
Morphological plastic responses to water depth and wave exposure in an aquatic plant (Myriophyllum spicatum)
- 2001
-
In: Journal of Ecology. - Oxford, United Kingdom : Wiley-Blackwell. - 0022-0477 .- 1365-2745. ; 89:2, s. 166-175
-
Journal article (peer-reviewed)abstract
- 1 We investigated morphological responses of the submerged macrophyte Myriophyllum spicatum L. to water depth and wave exposure when grown in the same substrate at two sites in two eutrophic lakes. Periphyton production was 4-8 times higher at sheltered than at wave-exposed sites and its influence was further investigated in a glasshouse experiment. Morphological responses in both experiments were compared by allometric analyses, with shoot weight as covariate. 2 In the field study, plants shoots exhibited similar responses (increased plant height and branch length, and decreased branch number) to sheltered conditions as to deep water. The partitioning between above- and below-ground biomass however, differed, with below-ground decreasing with an increasing water depth, but increasing or remaining unaffected at sheltered compared with exposed conditions. 3 In the glasshouse experiment, plant responses to water depth were similar to those in the field study. Furthermore, plant height increased when plants were overgrown with periphyton. 4 High production of periphytic algae at sheltered sites appears to cause light limitation of macrophytes. However, other factors such as nutrient uptake also appears to determine morphological responses. At sheltered sites, where leaf nutrient uptake is reduced by abundant periphyton and thick boundary layers, plants allocate more biomass to roots. At deep and wave-exposed sites, the absence of periphyton allows plants to take up nutrients through their leaves and allocation of biomass to shoots increases photosynthesis. 5 Overall, relative allocation to shoot and root biomass appears to be primarily controlled by nutrient availability, whereas allocation of available shoot biomass to particular structures is controlled by light availability.
|
|
| 22. |
- Strand, John A., et al.
(author)
-
Phenotypic plasticity – contrasting species-specific traits induced by identical environmental constraints
- 2004
-
In: New Phytologist. - Oxford : Blackwell. - 0028-646X .- 1469-8137. ; 163:3, s. 449-451
-
Journal article (peer-reviewed)abstract
- Can it be assumed that a specific environmental constraint imposed on different species leads to a convergence in, for example, morphology? A phenotype expressed in response to external stimuli (e.g. size-reduction in response to mechanical stress) should be adaptive regardless of species – this is largely intuitive, but has been poorly studied. In this issue (pp. 651–660), Puijalon & Bornette reveal exciting new data that suggest that phenotypic plastic responses to identical environmental constraints may indeed be species-specific (Puijalon & Bornette, 2004).
|
|
| 23. |
|
|
| 24. |
- Strand, J., et al.
(author)
-
Butyltin compounds in sediment and molluscs from the shipping strait between Denmark and Sweden
- 2003
-
In: Environmental Pollution. - 0269-7491. ; 124:1, s. 7-15
-
Journal article (peer-reviewed)abstract
- The distribution of tributyltin (TBT) contamination in the subtidal zone of the waters between Denmark and Sweden was investigated in relation to major international shipping lanes. Sediment and different benthic molluscs were sampled in transects along and perpendicularly to the shipping lanes in the Sound (Oresund) and the Kattegat/Skagerrak region. The samples were analysed for TBT and its degradation products, dibutyltin (DBT) and monobutyltin (MBT), using GC-PFPD. In sediments, the TBT concentration ranged from < 1 to 19 ng g(-1) dry weight (dw) with a strong correlation between the TBT concentration and the organic fraction in sediment (r(2) = 0.90) in the samples collected in the Sound, where the highest concentrations were found. This relationship was not observed in the samples from the Kattegat because the TBT concentration in most sediment samples was below the limit of detection. In the molluscs, TBT and its degradation products were detected in all samples from the entire area with concentrations ranging from 8.1 ng g(-1) dw in Buccinum undatum to 1316 ng g(-1) dw in Nuculana pernula. The deposit-feeding bivalve N. pernula was found to have a particularly high accumulation potential for TBT. In addition, a strong correlation between TBT concentrations in sediment and N. pernula was found. Therefore this species seems to be an ideal organism for monitoring sediment contamination. The TBT concentration in N. pernula was found to decrease gradually along the shipping lanes from the Sound, through the Kattegat and into the Skagerrak. (C) 2003 Published by Elsevier Science Ltd.
|
|
| 25. |
|
|
| 26. |
- Svensson, Jonas M., et al.
(author)
-
Rikare mångfald och mindre kväve : Utvärdering av våtmarker skapade med stöd av lokala investeringsprogram och landsbygdsutvecklingsstöd
- 2004
-
Book (other academic/artistic)abstract
- På uppdrag av Naturvårdsverket och Jordbruksverket har Våtmarkscentrum, Högskolan i Halmstad, utvärderat svenska våtmarker anlagda med landsbygdsutvecklingsstöd, LBU-stöd (Miva, projektstöd och Lmiva utan projektstöd) respektive våtmarker anlagda inom lokala investeringsprogram (LIP) avseende näringsretention och biologisk mångfald. Resultaten från utvärderingen redovisas separat för de fyra olika grupperna/kategorierna av anlagda våtmarker enligt nedan (fetstil anger kategorihänvisning i text, tabeller och figurer):• Våtmarker anlagda med anläggningsstöd inom Lokala investeringsprogram 1998 - 2002, LIP.• Våtmarker anlagda med anläggningsstöd inom LBU-projektstöd (dessa våtmarker får vanligen även skötselstöd, Lmiva), 2000 - 2002.• Våtmarker anlagda 1996-1999, utan anläggningsstöd men med skötselstöd (Miljöstöd), Miva.• Våtmarker anlagda från år 2000 - , utan anläggningsstöd men med skötselstöd (LBU-våtmarker som endast får skötselersättning), Lmiva.Syftet har främst varit att utvärdera och jämföra hur våtmarksanläggning inom olika stödformer har bidragit till minskad övergödning och ökad biologisk mångfald. Syftet har alltså inte varit att utvärdera enskilda våtmarker utan att ge en helhetsbild för olika stödformer och regioner. Därför har det varit nödvändigt att basera utvärderingen på data för ett stort antal våtmarker. Detta innebär att utförliga mätningar ej kunnat genomföras inom de enskilda objekten. Närsaltsretention har därför beräknats baserat på modeller och biologisk mångfald har undersökts genom att trollsländor använts som indikatorgrupp.Inom uppdraget har, med jordbruksstöd, registrerats information om totalt 908 våtmarksobjekt om totalt 2860 ha ersatt yta fördelat på 1815 ha Miva, 920 ha projektstöd och 125 ha Lmiva utan projektstöd. Totalt registrerade våtmarker med stöd från LIP är 274 st, omfattande 439 ha.Kompletterande fältstudier har utförts i drygt 100 st våtmarker. Främst är det resultaten från dessa våtmarker som sammanfattas nedan...
|
|
| 27. |
- Tala, TJJ, et al.
(author)
-
Comparison of theory-based and semi-empirical transport modelling in JET plasmas with ITBs
- 2002
-
In: Plasma Physics and Controlled Fusion. - 1361-6587 .- 0741-3335. ; 44:Suppl. 5A, s. A495-A500
-
Journal article (peer-reviewed)abstract
- The theory-based Weiland transport model has been applied to JET discharges with internal transport barriers (ITBs) for the first time. The agreement of the modelling results with the experiments has been found to be comparable with the agreement of the modelling results produced by the semi-empirical Bohm/gyro-Bohm transport model. Weiland model overestimates the width of the ITB and the electron temperature. There is evidence that the density gradient in the Weiland model plays a more important role in governing the ITB formation dynamics for JET discharges than the suppression of turbulence by the omega(ExB) flow shearing rate.
|
|
| 28. |
- Vretare, Viveka, et al.
(author)
-
Phenotypic plasticity in Phragmites australis as a functional response to water depth
- 2001
-
In: Aquatic Botany. - Amsterdam, Netherlands : Elsevier. - 0304-3770 .- 1879-1522. ; 69:2-4, s. 127-145
-
Journal article (peer-reviewed)abstract
- We have performed investigations to see if the emergent macrophyte Phragmites australia (Cav.) Trin. ex Steud. exhibits phenotypic plasticity as a response to water depth and if such responses in biomass allocation pattern and morphology are functional responses, improving the performance of the plant. In greenhouse experiments plants were grown in deep or shallow water to evaluate plastic responses. Allometric methods were used to handle effects caused by size differences between treatments. To evaluate if phenotypic responses to water depth are functional, the relative growth rate (RGR) of plants acclimatised to shallow or deep water, respectively, were compared in deep water, and the growth of plants in fluctuating and constant water level were compared. When grown in deep (70 or 75 cm), compared to shallow (20 or 5 cm) water, plants allocated proportionally less to below-ground weight, made proportionally fewer but taller stems, and had rhizomes that were situated more superficially in the substrate. Plants acclimatised to shallow water had lower RGR than plants acclimatised to deep water, when they were grown in deep water, and plants in constant water depth (40 cm) grew faster than plants in fluctuating water depth (15/65 cm). In an additional field study, the rhizomes were situated superficially in the sediment in deep, compared to shallow water. We have shown that P. australis acclimatises to deep water with phenotypic plasticity through allocating more resources to stem weight, and also by producing fewer but taller stems, which will act to maintain a positive carbon balance and an effective gas exchange between aerial and below-ground parts. Furthermore, the decreased proportional allocation to below-ground parts probably results in decreased nutrient absorption, decreased anchorage in the sediment and decreased carbohydrate reserves. Thus, in deep water, plants have an increased risk of becoming uprooted and experience decreased growth and dispersal rates. (C) 2001 Elsevier Science B.V. All rights reserved.
|
|
| 29. |
- Weisner, Stefan E. B., et al.
(author)
-
Ecology and management of plants in aquatic ecosystems
- 2002
-
In: Handbook of ecological restoration. - Cambridge : Cambridge University Press. - 0521791286 ; , s. 242-256
-
Book chapter (peer-reviewed)abstract
- The central role of macrophytes for the functioning of aquatic systems means that the most effective way to manage these systems is often through vegetation management. For this we need to understand the mechanisms regulating vegetation distribution. Submerged macrophyte distribution is mainly related to water depth, water transparency and epiphytic growth. The distribution of emergent vegetation can largely be predicted from water depth and substrate characteristics. Also, in both submerged and emergent macrophytes, the effects on the vegetation of grazing can be dramatic. Management should aim at providing environmental conditions favouring the desired ecosystem state, rather than methods directly aimed at the vegetation. For example, the best method for promoting establishment of emergent vegetation is often lowering of the water level. To establish submerged vegetation, water transparency can be increased through biomanipulation (the removal of zooplanktivorous fish leading to increased zooplankton grazing pressure on phytoplankton). Changes in water depth and introduction of grazers are often effective measures to control growth of aquatic weeds.
|
|
