Changes in plant community diversity and management effects in semi-natural meadows in southern Sweden
Abstract: The objectives of this thesis were to: 1) survey the vegetation in semi-natural meadows in south-central Sweden, 2) discern meadow vegetation changes in eight semi-permanent plots between studies performed in the 1960s and in 1990, 3) experimentally investigate the effects of variations in management intensity in one dry and one mesic meadow, 4) experimentally investigate the effects of different management practices or absence of management on species dynamics in meadow vegetation. 1. In the survey of meadows nine plant communities were recognised, ranging from wet to dry. The most obvious difference between investigated years was the decrease in plant community diversity. Thus two wet-moist plant communities found in the earlier study were missing in 1990, and one had more or less disappeared. 2. The comparison of semi-permanent plots studied in the 1960s and again in 1990 revealed changes in the vegetation within the plant communities. These were, e.g. increased cover of vascular plants, increased cover and number of graminoids, and increased cover of species with primary habitats others than grassland as well as decreased cover of species supposed to be favoured by mowing. Furthermore, considerable species dynamics were found. 3. Dry meadow vegetation was more prone to changes than mesic meadow vegetation, both in plots where the present management was simulated, as well as in totally unmanaged plots. Both raking and grazing had positive effects on species abundance in the mesic meadow. In the dry meadow raking had both positive and negative effects on species abundance, whereas grazing had almost only negative effects. When management was abandoned species richness declined, more so in the mesic meadow were several species disappeared already after one year of abandonment. 4. The mesic meadow was highly dynamic at the smallest scale studied (0.01 m2), e.g. the vegetation turnover index was twice as high at the 0.01-m2 scale as at the larger scales. Species dynamics increased if management was intensified, as well as when it was abandoned. However, in the most intensively managed plots, the increased species dynamics was due to the appearance of species, whereas in unmanaged plots it was due to the disappearance of species.
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