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Sökning: WFRF:(Marteinsdóttir Bryndís)

  • Resultat 1-10 av 15
  • [1]2Nästa
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  • Astor, Tina, et al. (författare)
  • Underdispersion and overdispersion of traits in terrestrial snail communities on islands
  • 2014
  • Ingår i: Ecology and Evolution. - 2045-7758 .- 2045-7758. ; 4:11, s. 2090-2102
  • Tidskriftsartikel (refereegranskat)abstract
    • Understanding and disentangling different processes underlying the assembly and diversity of communities remains a key challenge in ecology. Species can assemble into communities either randomly or due to deterministic processes. Deterministic assembly leads to species being more similar (underdispersed) or more different (overdispersed) in certain traits than would be expected by chance. However, the relative importance of those processes is not well understood for many organisms, including terrestrial invertebrates. Based on knowledge of a broad range of species traits, we tested for the presence of trait underdispersion (indicating dispersal or environmental filtering) and trait overdispersion (indicating niche partitioning) and their relative importance in explaining land snail community composition on lake islands. The analysis of community assembly was performed using a functional diversity index (Rao's quadratic entropy) in combination with a null model approach. Regression analysis with the effect sizes of the assembly tests and environmental variables gave information on the strength of under- and overdispersion along environmental gradients. Additionally, we examined the link between community weighted mean trait values and environmental variables using a CWM-RDA. We found both trait underdispersion and trait overdispersion, but underdispersion (eight traits) was more frequently detected than overdispersion (two traits). Underdispersion was related to four environmental variables (tree cover, habitat diversity, productivity of ground vegetation, and location on an esker ridge). Our results show clear evidence for underdispersion in traits driven by environmental filtering, but no clear evidence for dispersal filtering. We did not find evidence for overdispersion of traits due to diet or body size, but overdispersion in shell shape may indicate niche differentiation between snail species driven by small-scale habitat heterogeneity. The use of species traits enabled us to identify key traits involved in snail community assembly and to detect the simultaneous occurrence of trait underdispersion and overdispersion.
  • Marteinsdottir, Bryndis, et al. (författare)
  • An experimental test of the relationship between small scale topography and seedling establishment in primary succession
  • 2013
  • Ingår i: Plant Ecology. - 1385-0237 .- 1573-5052. ; 214:8, s. 1007-1015
  • Tidskriftsartikel (refereegranskat)abstract
    • In infertile environments, the spatial scale and distribution of favourable microsites may be an important determinant of vegetation patterns. Such patterns may be persistent although the association and causality may only be detectable during initial establishment. In this study we investigated experimentally how spatial variation on two different scales and species-specific traits affected seedling survival at an early successional site on SkeiA degrees ararsandur, a 1,000 km(2) homogeneous glacial outwash plain in SE-Iceland. Seedlings of eight native species were transplanted into six different micro-topographical combinations: three types of microsites (lee side of small stones and cushion plants, and control), located within two topographical features (shallow depressions and surrounding flats). Seedling survival was then recorded. Only 11 % of transplanted seedlings survived through the second winter, however seedlings that survived past the second growing season were likely to persist. Survival rates varied by species and were positively linked to seed size. Seedling survival was only weakly associated with spatial variation. The strongest association found was that survival was sometimes higher on flats compared to depressions. Sand accumulation in depressions might lower seedling survival there. We conclude that early plant establishment at the site, and the emergent vegetation mosaic, is most likely produced by the interaction of stochastic factors, such as the sand storms that intermittently rage across the plain and species-specific properties like seed size. However, in better-vegetated areas of SkeiA degrees ararsandur depressions often have higher moss and vascular plant cover than nearby flats, suggesting that moss may control vegetation patterns seen later in succession.
  • Marteinsdottir, Bryndis, 1980- (författare)
  • Assembly of plant communities in grasslands : an overview
  • 2009
  • Bok (övrigt vetenskapligt)abstract
    • How plants are arranged into communities is one of the central questions in plant ecology. One view holds that plant assembly is governed by deterministic factors, like assembly rules, while another holds that it is mostly stochastic, only constrained by the ability of plants to disperse and survive under the current environmental conditions. Here, I summarize studies on grassland community assembly, and try to find general patterns and rules. Of the 40 reviewed studies, evidence of deterministic assembly was found in 15, while evidence for stochastic assembly was found in nine. Evidence for both factors together was found in the remaining 16 studies. The studies varied in their use of methods, measured variables and scale, making them hard to compare. Even within a single study, results were dependent on the factors mentioned above. Plant community assembly of grasslands is a complex process, affected by assembly rules, environmental filtering and stochastic factors (e.g. dispersal limitation and priority effects) and which factor has the most influence seems to be site specific. More detailed and coordinated research is needed to determine what controls community assembly in grasslands.
  • Marteinsdottir, Bryndis, et al. (författare)
  • Development of vegetation patterns in early primary succession
  • 2010
  • Ingår i: Journal of Vegetation Science. - 1100-9233 .- 1654-1103. ; 21:3, s. 531-540
  • Tidskriftsartikel (refereegranskat)abstract
    • Question We investigated colonisation filters in early plant community development on a glacial outwash plain. We asked if these were related to seed limitation or to a lack of safe sites, if topographical heterogeneity affected species patchiness and how species life cycles influence successional trajectories. Location An outwash plain (Skeithararsandur) in southeast Iceland. Methods We identified surface heterogeneity at two different scales, ca. 10-15 cm (larger stones and established plants) and ca. 50 m (shallow depressions representing dry river beds) at two study sites. We quantified species cover, flowering plant density, seed production, seed rain, seed bank density, seedling emergence and seedling survival from June 2005 to June 2007 for the whole plant community, and measured seed production for five species. Results Mean vegetation cover was < 2.5% at the sites. Low emergence rates and high seedling mortality were the two main recruitment filters. Only 1.4% of seedlings emerging in 2005 survived into the 2007 growing season. Topographical heterogeneity had little effect on plant colonisation. High annual variation was recorded, and the two study sites (ca. 2 km apart) differed in their colonisation success. Of the five species, establishment of Cerastium alpinum and Silene uniflora was most limited by lack of seeds, whereas establishment of Luzula spicata, Poa glauca and Rumex acetosella was most limited by safe sites. Conclusions We conclude that colonisation processes and patterns in early primary succession on Skeithararsandur were largely influenced by stochastic factors.
  • Marteinsdóttir, Bryndís, 1980- (författare)
  • Plant community assembly in grazed grasslands
  • 2014
  • Doktorsavhandling (övrigt vetenskapligt)abstract
    • Species assembly into local communities from the surrounding region can be caused either by species failure to reach the site (i.e. seed limitation) or to establish (i.e. establishment limitation). The aim of this thesis was to investigate plant species assembly and to determine the relative importance of different factors in that process.In a cultivated landscape in southeast Sweden, plant community assembly was studied in grazed ex-arable fields. Community assembly from the surrounding region into the local community was explored using trait-based null models and seed sowing and transplanting experiments. The influence of local environmental factors and landscape history and structure on community assembly was also studied. In addition, differences in species assembly between ex-arable fields and semi-natural grasslands were explored.Seed limitation was the strongest filter on local community assembly. Only a fraction (36%) of species in a region dispersed to a local site and adding seeds/transplants increased species establishment. Species abundance at the regional scale, species dispersal method and seed mass strongly influenced which species arrived at the local sites. Establishment limitation also affected the assembly. Of species arriving at a site 78% did establish, seedling survival was low and which species established was influenced by species interactions, local environmental conditions and stochastic events. In addition, landscape structure that determined the species richness in the regional species pool influenced the local assembly. The comparison between assembly in ex-arable fields and semi-natural grasslands indicated that the main cause of difference in species assembly between them was difference in their age.The main conclusion of this thesis is that regional processes are more important than local factors in determining plant community assembly.
  • Marteinsdottir, Bryndis, 1980-, et al. (författare)
  • Plant community assembly in semi-natural grasslands and ex-arable fields : a trait-based approach
  • 2014
  • Ingår i: Journal of Vegetation Science. - 1100-9233 .- 1654-1103. ; 25:1, s. 77-87
  • Tidskriftsartikel (refereegranskat)abstract
    • QuestionThe assembly of plants into communities is one of the central topics in plant community ecology. The objective of this study was to investigate how plant functional trait diversity and environmental factors influence community assembly in two different grassland communities, and if variation in these factors could explain the difference in species assembly between these communities. LocationSix grazed ex-arable fields and eight semi-natural grasslands in southeast Sweden. MethodsWe estimated species abundance and measured soil attributes at each site. For each species within each site we measured specific leaf area (SLA), leaf dry matter content (LDMC) and seed mass. We analysed the data both for abundance-weighted species values and species occurrence. ResultsTrait gradient analysis indicated random distribution of species among sites, while CCA analysis indicated that both soil phosphorus and moisture were related to species assembly at a site. Correlations and fourth-corner analysis also revealed a relationship between measured species traits and soil phosphorus and moisture. There was a lower average seed mass and higher SLA of species in ex-arable fields compared to species in semi-natural grasslands. ConclusionsEven though trait gradient analysis indicated that plant community assembly in the studied grasslands was random, other results implied that species occurrence and abundance was influenced both by environmental factors and species traits. Higher species richness in semi-natural grasslands was associated with more large-seeded species found there compared to ex-arable fields, indicating that large-seeded species establish in grasslands later than small-seeded species.
  • Marteinsdottir, Bryndis (författare)
  • Seed Rain and Seed Bank Reveal that Seed Limitation Strongly Influences Plant Community Assembly in Grasslands
  • 2014
  • Ingår i: PLOS ONE. - 1932-6203. ; 9:7, s. e103352-
  • Tidskriftsartikel (refereegranskat)abstract
    • Dispersal is an important factor in plant community assembly, but assembly studies seldom include information on actual dispersal into communities, i.e. the local propagule pool. The aim of this study was to determine which factors influence plant community assembly by focusing on two phases of the assembly process: the dispersal phase and the establishment phase. At 12 study sites in grazed ex-arable fields in Sweden the local plant community was determined and in a 100-m radius around the centre of each site, the regional species pool was measured. The local seed bank and the seed rain was explored to estimate the local propagule pool. Trait-based models were then applied to investigate if species traits (height, seed mass, clonal abilities, specific leaf area and dispersal method) and regional abundance influenced which species from the regional species pool, dispersed to the local community (dispersal phase) and which established (establishment phase). Filtering of species during the dispersal phase indicates the effect of seed limitation while filtering during the establishment phase indicates microsite limitation. On average 36% of the regional species pool dispersed to the local sites and of those 78% did establish. Species with enhanced dispersal abilities, e.g. higher regional abundance, smaller seeds and dispersed by cattle, were more likely to disperse to the sites than other species. At half the sites, dispersal was influenced by species height. Species establishment was however mainly unlinked to the traits included in this study. This study underlines the importance of seed limitation in local plant community assembly. It also suggests that without information on species dispersal into a site, it is difficult to distinguish between the influence of dispersal and establishment abilities, and thus seed and microsite limitation, as both can be linked to the same trait.
  • Marteinsdóttir, Bryndís, 1980-, et al. (författare)
  • Trait-based filtering from the regional species pool into local grassland communities
  • 2014
  • Ingår i: Journal of Plant Ecology. - 1752-9921 .- 1752-993X. ; 7:4, s. 347-355
  • Tidskriftsartikel (refereegranskat)abstract
    • For plants to establish in a local community from a pool of possible colonizers from the region, it must pass through a series of filters. Which of the filters is most important in this process has been much debated. In this study, we explored how species are filtered from the regional species pool into local communities. The aim was to determine if differences in species abundance and functional traits could explain which species from the regional species pool establish at the local scale and if the filtering differed between grassland communities.This study took place in a cultivated landscape in southeastern Sweden. We estimated plant species abundance in 12 ex-arable field sites and 8 adjacent seminatural grassland sites and in a 100-m radius around the center of each site. We used Monte Carlo simulations to examine if species abundance and functional traits (height, seed mass, clonal abilities, specific leaf area and dispersal method) controlled the filtering of species from the regional pool into local communities.On average, only 28% of species found in the regional pool established in the ex-arable field sites and 45% in the seminatural grassland sites, indicating that the size of the regional species pool was not limiting local richness. For both grassland types, species abundance in the regional pool was positively correlated with species occurrence at the local scale. We found evidence for both species interaction filtering and dispersal limitation influencing the local assembly. Both local and regional processes were thus influencing the filtering of species from the regional species pool into local communities. In addition, the age of the communities influenced species filtering, indicating that community assembly and the importance of different filters in that process change over succession.
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