| 1. |
- Andersson, Andreas, et al.
(författare)
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Enhanced Air–Sea Exchange of Heat and Carbon Dioxide Over a High Arctic Fjord During Unstable Very-Close-to-Neutral Conditions
- 2019
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Ingår i: Boundary-layer Meteorology. - : Springer Science and Business Media LLC. - 0006-8314 .- 1573-1472. ; 170:3, s. 471-488
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Tidskriftsartikel (refereegranskat)abstract
- Eddy-covariance measurements made in the marine atmospheric boundary layer above a high Arctic fjord (Adventfjorden, Svalbard) are analyzed. When conditions are unstable, but close to neutral −0.1 < z/L < 0, where z is the height, and L is the Obukhov length, the exchange coefficient for sensible heat CH is significantly enhanced compared with that expected from classical surface-layer theory. Cospectra of the vertical velocity component (w) and temperature (T) reveal that a high-frequency peak develops at f ≈ 1 Hz for z/L > − 0.15. A quadrant analysis reveals that the contribution from downdrafts to the vertical heat flux increases as conditions become close to neutral. These findings are the signature of the evolving unstable very-close-to-neutral (UVCN) regime previously shown to enhance the magnitude of sensible and latent heat fluxes in the marine surface layer over the Baltic Sea. Our data reveal the significance of the UVCN regime for the vertical flux of the carbon dioxide (CO2) concentration (C). The cospectrum of w and C clearly shows how the high-frequency peak grows in magnitude for z/L > − 0.15, while the high-frequency peak dominates for z/L > − 0.02. As found for the heat flux, the quadrant analysis of the CO2 flux shows a connection between the additional small-scale turbulence and downdrafts from above. In contrast to the vertical fluxes of sensible and latent heat, which are primarily enhanced by the very different properties of the air from aloft (colder and drier) during UVCN conditions, the increase in the air–sea transfer of CO2 is possibly a result of the additional small-scale turbulence causing an increase in the water-side turbulence. The data indicate an increase in the gas-transfer velocity for CO2 for z/L > − 0.15 but with a large scatter. During the nearly 2 months of continuous measurements (March–April 2013), as much as 36% of all data are associated with the stability range −0.15 < z/L < 0, suggesting that the UVCN regime is of significance in the wintertime Arctic for the air–sea transfer of heat and possibly also CO2.
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| 2. |
- Andersson, Erik, et al.
(författare)
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Ambio fit for the 2020s
- 2022
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Ingår i: Ambio. - : Springer Nature. - 0044-7447 .- 1654-7209. ; 51:5, s. 1091-1093
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Tidskriftsartikel (refereegranskat)
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| 3. |
- Andersson, Elisabeth, et al.
(författare)
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Effects of river fragmentation on plant dispersal and riparian flora
- 2000
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Ingår i: Rivers Research and Applications. - 1535-1459 .- 1535-1467. ; 16:1, s. 83-89
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Tidskriftsartikel (refereegranskat)abstract
- We evaluated the effects of river fragmentation by dams on hydrochory (i.e. plant dispersal by water) and on plant distribution by comparing two adjacent rivers in northern Sweden, one free-flowing and the other regulated. We collected stranded drift material from both rivers in order to quantify the drift material and its species content. We also estimated the floristic continuity along the two rivers by comparing the drift flora with the riparian flora further upstream. The drift amount deposited on the riverbank, its species richness and its contribution to the species pool were higher in the free-flowing than in the regulated river. The floristic continuity was also higher in the free-flowing than in the regulated river.
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| 4. |
- Andersson, Elisabeth, et al.
(författare)
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Plant dispersal in boreal rivers and its relation to the diversity of riparian flora
- 2000
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Ingår i: Journal of Biogeography. - : Wiley. - 0305-0270 .- 1365-2699. ; 27:5, s. 1095-1106
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Tidskriftsartikel (refereegranskat)abstract
- Aim The paper has four major objectives: (1) to determine whether diaspore mimics accurately represent dispersal dynamics of real diaspores in a free-flowing river; (2) to estimate distance travelled and reasons for stranding of floating diaspores along a free-flowing river; (3) to test if species composition and seedling recruitment vary with the ability of the riverbank to trap waterborne drift; and (4) to compare diaspore dispersal in a free-flowing river with that in a regulated river where current velocity has been reduced. Location The field work was conducted in two 7th-order boreal rivers in northern Sweden, the free-flowing Vindel River and the regulated Ume River. Methods We performed a series of dispersal experiments. We tested the usefulness wooden cubes of diaspore mimics for performing dispersal experiments by releasing cubes and achenes of Helianthus annuus and compare their dispersal patterns in the free-flowing Vindel River. We used the cubes to identify 50-m long sections along the river with different trapping capacity, i.e. the number of stranded diaspore mimics within a 50-m section. We then related the number of stranded diaspore mimics to the vascular plant flora, the proportions of species with long or short floating times (i.e. more than or less than 2 days, respectively), the number of seedlings, and to environmental variables within the sections. We also released wooden cubes in a run-of-river impoundment to determine the dispersal capacity of diaspores in a regulated river. Results The cubes were useful as diaspore mimics. They dispersed similarly to achenes of H. annuus. The stranding pattern of diaspore mimics was significantly associated with water current. Species richness of vascular plants per 50-m section increased with the number of stranded mimics. Seedling recruitment, and the proportions of species with short-floating and long-floating diaspores, did not vary with the number of stranded mimics. The ability of a river to transport diaspores downstream was strongly reduced by impoundment. Main conclusions We conclude that patterns of species richness of riparian vegetation is in part determined by the ability of the riverbank to trap waterborne diaspores, but differences in floating ability among species did not affect the species composition along free-flowing rivers.
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| 5. |
- Andersson, E., et al.
(författare)
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Temporal variation in the drift of plant litter and propagules in a small boreal river
- 2002
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Ingår i: Freshwater Biology. - : Wiley. - 0046-5070 .- 1365-2427. ; 47:9, s. 1674-1684
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Tidskriftsartikel (refereegranskat)abstract
- 1. Rivers are linear ecosystems across landscapes with an effective transport of organisms, sediment and organic matter. Dispersal is studied mostly during single events and for single species, and there is little knowledge on how the drift of plant litter and propagules varies within and between years for entire communities. 2. We used floating traps for collecting waterborne plant litter and propagules in a small boreal river over 2 years. We installed the traps at four different locations along the river, and emptied them at least once a week during the ice-free season. We analysed propagule content by sorting and identifying species and through germination tests on bare soil. 3. In total, we recorded at least 54 taxa in the samples, and the highest density recorded in one sample was 5000 propagules per 100 g litter (dry weight). Large temporal variations in litter and propagule transport were revealed, both within and between years. 4. The longitudinal pattern was consistent between years, with an increasing mass of litter and number of propagule taxa downstream. The results highlight the importance of the temporal and longitudinal dimensions in river management.
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| 6. |
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| 7. |
- Bratt, Katarina, et al.
(författare)
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Avenanthramides in Oats (Avena Sativa L.) and Structure-Activity Relationships
- 2003
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Ingår i: Journal of Agricultural and Food Chemistry. - : American Chemical Society (ACS). - 0021-8561 .- 1520-5118. ; 51:3, s. 594-600
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Tidskriftsartikel (refereegranskat)abstract
- Eight avenanthramides, amides of anthranilic acid (1) and 5-hydroxyanthranilic acid (2), respectively, and the four cinnamic acids p-coumaric (p), caffeic (c), ferulic (f), and sinapic (s) acid, were synthesized for identification in oat extracts and for structure−antioxidant activity studies. Three compounds (2p, 2c, and 2f) were found in oat extracts. As assessed by the reactivity toward 1,1-diphenyl-2-picrylhydrazyl (DPPH), all avenanthramides except 1p showed activity. Initially, the antioxidant activity of the avenanthramides decreased in a similar order as for the corresponding cinnamic acids, that is: sinapic > caffeic > ferulic > p-coumaric acid. The avenanthramides derived from 2 were usually slightly more active than those derived from 1. All avenanthramides inhibited azo-initiated peroxidation of linoleic acid. 1c and 1s were initially the most effective compounds. The relative order of antioxidant activities was slightly different for the DPPH and the linoleic acid assays run in methanol and chlorobenzene, respectively.
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| 8. |
- Hildingsson, Ingegerd, et al.
(författare)
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Swedish women's expectations about antenatal care and change over time - A comparative study of two cohorts of women
- 2014
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Ingår i: Sexual and Reproductive Healthcare. - : Elsevier BV. - 1877-5764 .- 1877-5756. ; 5:2, s. 51-57
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Tidskriftsartikel (refereegranskat)abstract
- A decade ago a national cohort of Swedish-speaking women were surveyed about their expectations on antenatal care. Today, antenatal care in Sweden still operates under similar circumstances while changes have occurred in society and the pregnant population. Objective: To compare expectations of antenatal care in pregnant women recruited 2009-2010 to those of pregnant women from a national cohort in 1999-2000. An additional aim was to compare antenatal expectations in women recruited to a clinical trial and subsequently received group based or standard antenatal care. Methods: A cross-sectional pre-study of 700 women recruited to a clinical trial and a historical cohort of 3061 women from a Swedish national survey. Data was collected by a questionnaire in early pregnancy for both cohorts and before the clinical trial started. Results: In early pregnancy 79% of the women in the study sample reported a preference for the recommended number of visits, which is slightly higher than in the national cohort (70%). Continuity of the caregiver was still important with 95% vs 97% of the women rated it important to meet the same midwife at subsequent antenatal visits. The content of care rank order showed a change over time with lower expectations in health check-ups and emotional content and higher expectations in information needs, respect and partner involvement. Conclusion: Women approached in early pregnancy had lower expectations about medical and emotional check-ups and parent education but higher expectations regarding information, being met with respect and the involvement of the partner compared to women 10. years ago. Continuity of a midwife caregiver was still important and women seem more willing to follow the recommended number of antenatal visits. Clinical implications: Asking women about their expectations regarding antenatal care could be a means to individualize the care. © 2014 Elsevier B.V.
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| 9. |
- Jansson, Roland, 1967-, et al.
(författare)
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Effects of river regulation on river-margin vegetation : A comparison of eight boreal rivers
- 2000
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Ingår i: Ecological Applications. - 1051-0761 .- 1939-5582. ; 10:1, s. 203-224
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Tidskriftsartikel (refereegranskat)abstract
- Regulation and fragmentation by dams belong to the most widespread deliberate impacts of humans on the world's rivers, especially in the Northern Hemisphere. We evaluated the effects of hydroelectric development by comparing the flora of vascular plants in 200-m-long reaches of river margin distributed along eight entire rivers in northern Sweden. Four of these rivers were free-flowing, and four were strongly regulated for hydroelectric purposes. First, we compared species diversity per site between entire free-flowing and regulated rivers. To reduce the effects of natural, between-river variation, we compared adjacent rivers. One regulated river had lower plant species richness and cover than two adjacent free-flowing ones, whereas two other parallel rivers, one regulated and another free-flowing, did not differ significantly. Second, river-margin vegetation responded differently to different types of regulated water-level regimes. Both along run-of-river impoundments, with small but daily water-level fluctuations, and along storage reservoirs, with large fluctuations between low water levels in spring and high levels in late summer and fall, the number of species and their cover per site were lower than along the free-flowing rivers. Regulated but unimpounded reaches were most similar to free-flowing rivers, having lower plant cover per site, but similar numbers of species. For reaches with reduced discharge, evidence was mixed; some variables were lower compared to free-flowing rivers whereas others were not. However, for the last two types of regulation, statistical power was low due to small sample sizes. Third, we classified all plant species according to their dispersal mechanisms and tested whether they respond differently to different types of regulated water-level regimes. Three out of four types of regulation had higher proportions of wind-dispersed species, and two out of four had lower proportions of species without specific mechanisms for dispersal, compared to free-flowing rivers, suggesting that dispersal ability is critical for persistence following regulation. Run-of-river impoundments had higher proportions of long-floating species and species with mechanisms for vegetative dispersal, suggesting that water dispersal may still be important despite fragmentation by dams. Fourth, plant species richness and cover varied with both local factors, such as water-level regime, and regional factors, such as length of the growing season. Presence of clay and silt in the river-margin soil, preregulation position of the contemporary river margin, non-reservoir sites, low altitudes, and long growing seasons were associated with high plant species richness and cover.
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| 10. |
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