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- Aggemyr, Elsa, et al.
(författare)
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Landscape structure and land use history influence changes in island plant composition after 100 years
- 2012
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Ingår i: Journal of Biogeography. - : Wiley. - 0305-0270 .- 1365-2699. ; 39:9, s. 1645-1656
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Tidskriftsartikel (refereegranskat)abstract
- Aim We investigated how current and historical land use and landscape structure affect species richness and the processes of extinction, immigration and species turnover. Location The northern part of the Stockholm archipelago, Baltic Sea, Sweden. We resurveyed 27 islands ranging from 0.3 to 33 ha in area. Methods We compared current plant survey data, cadastral maps and aerial photographs with records obtained from a survey in 1908, using databases and a digital elevation model to examine changes in plant community dynamics in space and time. We examined the effects of local and landscape structure and land use changes on plant species dynamics by using stepwise regression in relation to eight local and three landscape variables. The eight local variables were area, relative age, shape, soil heterogeneity, bedrock ratio, number of houses, forest cover change, and grazing 100 years ago. The three landscape variables were distance to mainland, distance to closest island with a farm 100 years ago, and structural connectivity. Hanskis connectivity measure was modified to incorporate both connectivity and fragmentation. Results The investigated islands have undergone drastic changes, with increasing forest cover, habitation, and abandonment of grassland management. Although the total species richness increased by 31% and mean island area by 23%, we found no significant increase in species richness per unit area. Local variables explain past species richness (100 years ago), whereas both local and landscape variables explain current species richness, extinctions, immigrations and species turnover. Grazing that occurred 100 years ago still influences species richness, even though grazing management was abandoned several decades ago. The evidence clearly shows an increase in nitrophilous plant species, particularly among immigrant species. Main conclusions This study highlights the importance of including land use history when interpreting current patterns of species richness. Furthermore, local environment and landscape patterns affect important ecological processes such as immigration, extinction and species turnover, and hence should be included when assessing the impact of habitat fragmentation and land use change. We suggest that our modified structural connectivity measure can be applied to other types of landscapes to investigate the effects of fragmentation and habitat loss.
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| 4. |
- Aggemyr, Elsa, et al.
(författare)
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Species richness and composition differ in response to landscape and biogeography
- 2018
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Ingår i: Landscape Ecology. - : Springer Science and Business Media LLC. - 0921-2973 .- 1572-9761. ; 33:12, s. 2273-2284
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Tidskriftsartikel (refereegranskat)abstract
- Context Understanding how landscape patterns affect species diversity is of great importance in the fields of biogeography, landscape ecology and conservation planning, but despite the rapid advance in biodiversity analysis, investigations of spatial effects on biodiversity are still largely focused on species richness.Objectives We wanted to know if and how species richness and species composition are differentially driven by the spatial measures dominating studies in landscape ecology and biogeography. As both measures require the same limited presence/absence information, it is important to choose an appropriate diversity measure, as differing results could have important consequences for interpreting ecological processes.Methods We recorded plant occurrences on 112 islands in the Baltic archipelago. Species richness and composition were calculated for each island, and the explanatory power of island area and habitat heterogeneity, distance to mainland and structural connectivity at three different landscape sizes were examined.Results A total of 354 different plant species were recorded. The influence of landscape variables differed depending on which diversity measure was used. Island area and structural connectivity determined plant species richness, while species composition revealed a more complex pattern, being influenced by island area, habitat heterogeneity and structural connectivity.Conclusions Although both measures require the same basic input data, species composition can reveal more about the ecological processes affecting plant communities in fragmented landscapes than species richness alone. Therefore, we recommend that species community composition should be used as an additional standard measure of diversity for biogeography, landscape ecology and conservation planning.
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| 5. |
- Auffret, Alistair G., et al.
(författare)
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Spatial scale and specialization affect how biogeography and functional traits predict long-term patterns of community turnover
- 2017
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Ingår i: Functional Ecology. - : Wiley. - 0269-8463 .- 1365-2435. ; 31:2, s. 436-443
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Tidskriftsartikel (refereegranskat)abstract
- 1. Immigration, extirpation and persistence of individual populations of species are key processes determining community responses to environmental change. However, they are difficult to study over long time periods without corresponding historical and modern-day species occurrences.2. We used historical and present-day plant species occurrence data from two different spatial scales (resolutions) to investigate the plant community turnover during the 20th century in a Baltic Sea archipelago. Patterns of turnover were analysed in relation to plant functional traits relating to dispersal and competition/persistence, as well as biogeographical variables.3. Turnover was largely driven by interactions between functional traits and measures of area, connectivity and distance to mainland. However, the combinations of traits and biogeographical variables that were most important for predicting immigration and extirpation differed between data sets, and between species associated with grassland management and the entire species pool.4. Taller plants were more likely to persist regardless of scale and biogeography, reflecting the grazing abandonment that occurred in the study area. Interactions between dispersal traits and biogeography were related to immigrations when the entire species pool was considered. However, increased dispersal potential, a smaller island size and increasing distance to mainland combined to promote extirpations in management-associated species. A perennial life span and seed banking contributed to species persistence. At the larger spatial scale, trait-driven turnover was not mediated by the biogeographical context.5. We showed that it is important to consider functional traits, biogeographical variables and their interactions when analysing community turnover over time. Furthermore, we found that the understanding of how combinations of traits and biogeography predict turnover depends on the source and spatial scale of the available data, and the species pool analysed.
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| 6. |
- Cousins, Sara A. O., et al.
(författare)
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The influence of field shape, area and surrounding landscape on plant species richness in grazed ex-fields
- 2008
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Ingår i: BIOLOGICAL CONSERVATION. - : Elsevier BV. - 0006-3207. ; 141, s. 126-135
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Tidskriftsartikel (refereegranskat)abstract
- Over the past 100 years species-rich semi-natural grasslands have decreased dramatically in Western Europe, where former arable fields (ex-fields) are used instead as pasture. The disappearance of semi-natural grasslands have caused a threat to the biodiversity in agricultural landscapes. Many typical grassland plants are dispersal limited, thus grazed ex-fields can be used to investigate if species spontaneously colonise these new grassland habitats. We examined the relationship between surrounding landscape, field area, shape, distance between edge and centre, and plant species diversity in ex-fields that had been grazed for 15-18 years. The results showed that there were 35% more plant species in fields surrounded by commercial forestry production compared to those surrounded by open agricultural landscape. Area and shape did not influence species richness, although there was increasing number of species in the centre with decreasing distance from the edge. 25% of the species where typical grassland species, and ex-fields surrounded by forest had 91% more grassland species compared to those in the open landscape. It is possible to increase grassland plant occurrences by grazing ex-fields surrounded by forest or other grassland remnant habitats, particularly in landscapes where grazed semi-natural grasslands are scarce.
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| 7. |
- Strandmark, Alma, et al.
(författare)
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Direct and indirect effects of island size and wave exposure on shoreline arthropod diversity
- 2020
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Ingår i: Journal of Biogeography. - : Wiley. - 0305-0270 .- 1365-2699. ; 47:4, s. 968-977
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Tidskriftsartikel (refereegranskat)abstract
- Aim Available theories suggest that the species number increases with island size, but the relationship between island size and species density, the number of species per unit area, is less understood. Moreover, mechanisms connecting island size and species density are not always evident because small and large islands differ in physical characteristics other than island size. The purpose here was to disentangle direct and indirect effects of island size and wave exposure on the species density of arthropods from herb-dominated shore habitats. Location Islands in the Stockholm Archipelago, Sweden. Taxon Spiders (Araneae) and beetles (Coleoptera). Methods We collected spiders and beetles on vegetated shores on islands of varying sizes, and used structural equation models to disentangle direct and indirect island size and wave exposure effects on species density. Results Island size affected diversity of web-building spiders, predatory beetles and other beetles (detritivores and omnivores), direct and indirectly. Indirect effects arose because large islands have more trees and steeper slopes than small islands, both of which affected species occurrence. Because height above the sea level reduces the effect of wave exposure, there were effects of these variables on the forest cover and on the diversity of web-building spiders. Finally, surrounding forest cover and diversity of flowering plants within sites increased diversity of herbivore beetles and cursorial spiders, likely because these sites provide more diverse resources. Main conclusions The result that predictors for species density vary between functional groups, with mechanisms that may or may not relate to island size, suggest potential developments in island biogeography theories. Future studies of island size effects should also attempt to quantify indirect effects, and not only total effects.
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