A palaeoecological test of the land-use hypothesis for recent lake acidification in South-West Norway using hill-top lakes |
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| Authors: | H J B Birks Frode Berge J F Boyle B F Cumming |
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| Institution: | (1) Botanical Institute, University of Bergen, Allégaten 41, N-5007 Bergen, Norway;(2) 2920 Leira, Valdres, Norway;(3) Department of Biology, Queen's University, K7L 3N6 Kingston, Ontario, Canada |
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| Abstract: | Lakes perched on hill-tops have very small catchments. Their water chemistry is largely influenced by the chemical composition of precipitation and by the underlying bedrock geology. They are ideal sites for testing the hypothesis that land-use and associated soil changes are a major cause of recent lake acidification. On this hypothesis, hill-top lakes in SW Norway are predicted not to show any recent lake acidification because, by their very nature, the chemistry of such lakes is little influenced by land-use or soil changes.Palaeolimnological analyses of diatoms and chrysophytes show that prior to ca. 1914 the two hill-top lakes investigated were naturally acid with reconstructed lake-pH values of at least 4.8–5.1. Since ca. 1914 lake pH values declined to ca. 4.5–4.7. These results contradict the land-use hypothesis. All the available palaeolimnological evidence (diatoms, chrysophytes, pollen, sediment geochemistry, carbonaceous particles) is consistent with the acid-deposition hypothesis.In the absence of any evidence to support the land-use hypothesis as a primary cause of recent lake acidification and in the light of several independent refutations, it is perhaps time to put the land-use hypothesis for recent lake acidification to rest. |
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| Keywords: | diatoms pollen chrysophytes heavy metals acidification land-use Norway pH changes |
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