| 1. |
- Vretare, Viveka, et al.
(författare)
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Phenotypic plasticity in Phragmites australis as a functional response to water depth
- 2001
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Ingår i: Aquatic Botany. - Amsterdam, Netherlands : Elsevier. - 0304-3770 .- 1879-1522. ; 69:2-4, s. 127-145
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Tidskriftsartikel (refereegranskat)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.
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| 4. |
- Weisner, Stefan E.B. 1954-
(författare)
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Factors affecting the internal oxygen supply of Phragmites australis (Cav.) Trin. ex Steudel in situ
- 1988
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Ingår i: Aquatic Botany. - Amsterdam : Elsevier. - 0304-3770 .- 1879-1522. ; 31:3-4, s. 329-335
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Tidskriftsartikel (refereegranskat)abstract
- Oxygen concentration in basal stems of Phragmites australis (Cav.) Trin. ex Steudel was measured in situ, in monospecific stands. The mean O2 concentration in basal stems, and mean shoot length above water, decreased in deeper water. Oxygen concentration in basal stems was correlated to shoot length above water at a given water depth, and the mean O2 concentration in basal stems of shoots with similar length above water decreased in deeper water. The results suggest that O2 transport from shoots to below-ground parts is restricted in deep water by: (1) small shoot length above water; (2) long O2 transport distance. No influence of substrate redox potential on O2concentration in basal stems was found. © Copyright 1988 Elsevier B.V.
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| 5. |
- Weisner, Stefan E.B. 1954-, et al.
(författare)
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Influence of germination time on juvenile performance of Phragmites australis on temporarily exposed bottoms – implications for the colonization of lake beds
- 1993
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Ingår i: Aquatic Botany. - Amsterdam, Netherlands : Elsevier. - 0304-3770 .- 1879-1522. ; 45:2-3, s. 107-118
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Tidskriftsartikel (refereegranskat)abstract
- Three cohorts of seedlings of Phragmites australis (Cav.) Trin ex Steud., germinated in May, June and July, were allowed to grow in shallow water (depth 5 cm or less) in southern Sweden. In the autumn, size parameters were measured on the plants. In the second year, the water level was raised to 0.8 m and emergence of shoots, plant survival and size parameters were recorded. The mean plant weight by the end of the first year differed markedly between cohorts. Rhizome biomass showed a relationship of 700:70:1 between the May, June and July cohorts. In the second year, rate of emergence above the water surface, and maximum height of plants that did not reach the water surface, was positively related to the size (mass) the plants had achieved after the first year. Only plants that emerged above the water surface survived the second summer, resulting in survival rates for the May, June and July cohorts of 90%, 68% and 0%, respectively. The rhizome weight of the smallest survivors had decreased after the second summer compared with values after the first summer. Hence, they were not capable of ‘reloading’ their rhizomes during the second year. In a temperate climate, the size of juvenile plants after the first year, which is strongly dependent on early germination on exposed bottoms (i.e. bottoms without standing water), determines their water depth tolerance during the second year. The timing and duration of exposure, as well as the subsequent depth of re-flooding, are all of fundamental importance for successful ‘lakeward’ seedling expansion of P. australis.
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| 6. |
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| 7. |
- Alström-Rapaport, Cecilia, et al.
(författare)
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Seasonal variation in the mode of reproduction of Ulva intestinalis in a brackish water environment
- 2010
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Ingår i: Aquatic Botany. - : Elsevier BV. - 0304-3770 .- 1879-1522. ; 93:4, s. 244-249
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Tidskriftsartikel (refereegranskat)abstract
- We explored the reproductive modes of Viva intestinalis in the inner part of the Baltic Sea during three consecutive years by using five microsatellite loci to estimate the relative abundance of diploid sporophytes and haploid gametophytes. Our results suggest that both diploid sporophytes and haploid gametophytes occur regularly in the Baltic Sea. The ratio of haploid to diploid individuals changes with seasons. Sporophytes are more abundant than gametophytes throughout the year, but the proportion of haploids increases from 10% in early summer to 35% in September. The over-wintering takes primarily place as diploid spores released by sporophytes. The sporophytes appear to reproduce both sexually and asexually in the Baltic Sea, since clones were found for this life phase. The fraction of individuals which belonged to an apparent diploid clone was higher in spring (62%) than in autumn (33%). We also found evidence for asexual clones in haploid gametophytes. The presence of both diploid and haploid individuals and the pattern of genetic and genotypic diversity provide evidence of sexual reproduction in the Baltic Sea. Thus the sporophytes and gametophytes do not function as two reproductively separate units. Compared with many other algal species with a reduced reproductive cycle in low salinity, U. intestinalis differs by having a multitude of reproductive modes also in the brackish water Baltic Sea, which can in part explain the dynamic propagation and high adaptability of the species.
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| 8. |
- Austin, Åsa N., 1988-, et al.
(författare)
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Stronger effect of individual species’ traits than shading on aquatic plant community productivity and interspecific competition
- 2023
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Ingår i: Aquatic Botany. - : Elsevier BV. - 0304-3770 .- 1879-1522. ; 187
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Tidskriftsartikel (refereegranskat)abstract
- Competition is one of the major factors structuring plant communities. Species with similar traits generally compete more intensely and have more similar yield than functionally dissimilar species, which often respond differently to environmental change. Little is known about how the interacting species’ traits influence the effect of environmental change on interspecific competition. However, theory predicts that environmental change should lead to more asymmetric competition, by favouring the species best adapted to the particular environmental change. Here we used a mesocosm experiment with three common aquatic plant species from the Baltic Sea (Northern Europe), to test how community productivity and competition asymmetry were affected by functional dissimilarity, individual species’ traits and a common stressor: shading. Competition asymmetry was defined as the absolute difference in reductions in yield relative to monocultures of two interacting species. Community productivity decreased and competition asymmetry increased with functional dissimilarity of the interacting species, possibly explained by the traits of the superior species, which had higher specific leaf area, maximum canopy height and primary production rate than the subordinate species. Community productivity was not affected by shading, contrary to our expectation, while competition asymmetry was higher in shaded than ambient conditions. Individual species yield depended on species identity and species combination. Only the shortest species was negatively affected by shading. Thus, by favouring tall-growing species, shading can alter interspecific competition. Together, these findings suggest that non-random species loss following environmental change can be caused by competitive exclusion, in addition to a direct effect of abiotic filtering.
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| 9. |
- Bastviken, David, et al.
(författare)
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The importance of plants for methane emission at the ecosystem scale
- 2023
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Ingår i: Aquatic Botany. - : ELSEVIER. - 0304-3770 .- 1879-1522. ; 184
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Tidskriftsartikel (refereegranskat)abstract
- Methane (CH4), one of the key long-lived atmospheric greenhouse gases, is primarily produced from organic matter. Accordingly, net primary production of organic matter sets the boundaries for CH4 emissions. Plants, being dominant primary producers, are thereby indirectly sustaining most global CH4 emissions, albeit with delays in time and with spatial offsets between plant primary production and subsequent CH4 emission. In addition, plant communities can enhance or hamper ecosystem production, oxidation, and transport of CH4 in multiple ways, e.g., by shaping carbon, nutrient, and redox gradients, and by representing a physical link be-tween zones with extensive CH4 production in anoxic sediments or soils and the atmosphere. This review focuses on how plants and other primary producers influence CH4 emissions with the consequences at ecosystem scales. We outline mechanisms of interactions and discuss flux regulation, quantification, and knowledge gaps across multiple ecosystem examples. Some recently proposed plant-related ecosystem CH4 fluxes are difficult to reconcile with the global atmospheric CH4 budget and the enigmas related to these fluxes are highlighted. Overall, ecosystem CH4 emissions are strongly linked to primary producer communities, directly or indirectly, and properly quantifying magnitudes and regulation of these links are key to predicting future CH4 emissions in a rapidly changing world.
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| 10. |
- Faithfull, C. L., et al.
(författare)
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Restoring charophytes is still a challenge: A call for developing successful methods
- 2024
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Ingår i: AQUATIC BOTANY. - 0304-3770 .- 1879-1522. ; 193
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Tidskriftsartikel (refereegranskat)abstract
- Submerged aquatic vegetation, and especially charophytes, which are an important habitat for many species, have declined in the Baltic Sea due to changes in light climate, eutrophication and physical disturbance. Physical disturbance in the form of small-scale dredging activities is commonplace in Sweden due to land uplift, but causes fragmentation of coastal habitats. Here we test three planting methods for restoration of the charophyte Chara aspera on an area of deposited sediment, and a single method for restoration of C. tomentosa in a dredged area. We found that none of the planting methods tested was more successful than natural recolonization of C. aspera on the deposited sediment. C. tomentosa planting was unsuccessful in the dredged area and was likely outcompeted for light by taller species. The C. aspera meadow was resilient to smaller disturbances, as experimental removal of up to 2.5% of C. aspera and sediment from the donor area did not reduce C. aspera coverage a month after removal. Even after an uncontrolled event that removed up to 50% of C. aspera in the experimental plots, C. aspera coverage had returned to pre-removal levels a year after the disturbance. We suggest future restoration experiments test transplanting sediment rich in oocytes and bulbils into areas with suitable light climates and low competition with other species. Restoration efforts are costly and highly uncertain of success, therefore we recommend discontinuing dredging activities in charophyte meadows to protect this important habitat.
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