Habitat level determinants of emergent macrophyte occurrence,extension and change in two large boreal lakes in Finland |
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Authors: | S Partanen M Luoto S Hellsten |
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Institution: | 1. Department of Geography, P.O. Box 3000, FI-90014 University of Oulu, Finland;2. Thule Institute, P.O. Box 7300, FI-90014 University of Oulu, Finland;3. Finnish Environment Institute, P.O. Box 413, FI 90014 University of Oulu, Finland |
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Abstract: | Historical (1947–1950) and present day (1998–2000) aerial photograph data of aquatic vegetation were combined with soil, land use and habitat morphology variables in two lakes, oligotrophic L. Näsijärvi (256 km2) and eutrophic L. Pyhäjärvi (122 km2), with regulated water levels in southern Finland. Multivariate GLM analyses were used to examine the determining factors of occurrence and horizontal extension of vegetation, occurrence of common reed (Phragmites australis) and water horsetail (Equisetum fluviatile) and the vegetation change in 474 sites. Despite differences in geography and water level regulation between the lakes, congruent trends were identified. The vegetation occurrence in both lakes had a positive response to clay soils and incoming nutrients and a negative response to housing and shore slope. Moraine soils, housing and shore slope had a negative effect on horizontal extension of vegetation in both lakes. The occurrence of P. australis was controlled by a negative response to moraine and the occurrence of E. fluviatile to slope in both lakes. The vegetation change in both lakes was characterized by a negative response to housing and slope. |
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Keywords: | Aerial photography Aquatic vegetation Equisetum fluviatile Habitat morphology Historical data Land use Phragmites australis Soil type |
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