Evidence for acidification-driven ecosystem collapse of Danish wet heathland

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We report observations of disappearance of
Erica tetralix in wet heathland, which is unlikely to be
caused by competition, as E. tetralix is dying before its
place is taken up by other species. To investigate the
causes, we used both old and new data. Results showed that
presence of Molinia caerulea and Calluna vulgaris were
substantial in the former E. tetralix dominated areas.
Measurements of the C/N ratio in the morlayer were
between 21 and 26 under the E. tetralix stands. As the
expected C/N ratio in a healthy nutrient poor ecosystem
like the E. tetralix wet heathland is around 30, this indicates
that the ratio is probably decreasing and, correspondingly,
the probability of nitrogen leaching from the
ecosystem is increasing. The morlayer pH was extremely
low—between 3.03 and 3.78. This represents a pH decline
since the 1960s, where pH values generally were above 4.
This supports the hypothesis that the decrease in morlayer
pH is the major factor explaining the disappearance of
E. tetralix and that measures to increase pH should be
considered as part of
Original languageEnglish
Issue number4
Pages (from-to)393-401
StatePublished - 2012

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