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Recruitment and distribution patterns of plants in Swedish semi-natural grasslands
Stockholm University.
1999 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Semi-natural pastures with different histories of management are nowadays the main remnants of the traditional agrarian landscape in southern Sweden. The aims of this thesis were to investigate the importance of features of the present-day landscape and its management history for species distribution and abundance patterns in Swedish semi-natural pastures, with a particular focus on factors affecting recruitment processes. Seedling recruitment in these semi-natural pastures was enhanced by disturbances, with the largest advantage for small-seeded species. The majority of species in semi-natural pastures have small seeds that germinate in the autumn. Seedlings seem to recruit mainly from the local species-pool, with 83 % of the recruited species found in the vegetation, whereas 44 % of the recruited species were found in the seed bank. Plant species diversity and distribution patterns are influenced by management history. In the study of distribution patterns of Thymus serpyllum I found that T. serpyllum populations were associated with Iron Age remnants, indicating that T. serpyllum is dependent on human activities, both for dispersal and for the maintenance of established populations. The highest species diversity was found in pastures with a long continuous management regime, whereas no significant species-area relationship could be detected in the present-day landscape. The highest arbuscular mycorrhizal colonization was also found in pastures with a long continuous management regime. The explanation for this patterns is probably that long continuous management is associated with an increasing likelihood of successful dispersal of plant species as well as of fungal species. Thus, historical distribution of pasture areas and their management history may be more important than the present-day distribution. The effects of the dramatic changes of the cultural landscape during this century, with fragmentation of the landscape and changing management, will work on other time scales. The fact that most species in semi-natural pastures are long-lived perennial species, implies that changes in species composition will be slow. Plantago media was found to have an overall negative population growth rate and a restricted dispersal ability, and this may be viewed as a first step towards visible changes. Dispersal limitation seems to be important in the present-day landscape, with T. serpyllum and P. media as examples of both local and regional dispersal limitation. The lack of area-relationship may also be an effect of "self-similarity" of grasslands. Indeed, I found that the majority of species (61%) in Swedish semi-natural pastures were recorded at the smallest spatial scale (0.01m2), and that the area sampled at this scale comprised only 1.25 % of the area examined. This indicates a small-scale structuring of diversity in these pastures.

Place, publisher, year, edition, pages
Stockholm: Stockholm University , 1999. , 28 p.
National Category
Research subject
Plant Ecology
URN: urn:nbn:se:su:diva-63838ISBN: 91-7153-889-5OAI: diva2:452851
Public defence
1999-05-08, 10:00
Härtill 6 uppsatserAvailable from: 2011-10-31 Created: 2011-10-31 Last updated: 2011-10-31Bibliographically approved

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