Evidence for climatic deteriorations associated with the decline of Sphagnum imbricatum Hornsch. ex Russ. in six ombrotrophic mires from northern England and the Scottish Borders

Abstract

The decline of Sphagnum imbricatum from the peat stratigraphy of six ombrotrophic mires (Bolton Fell Moss and Walton Moss, Raeburn Flow and Bell's Flow, and Coom Rigg Moss and Felecia Moss), has been investigated using colorimetric humification, quantitative plant macrofossil, and testate amoebae analyses. The chronology of each peat profile was determined by radiocarbon assay and pollen/land-use correlations. Palaeoclimate reconstructions have been made by linking known documentary/historical changes in climate, and other proxy-climate records, to those inferred from the sites investigated in the study region. In two of the ombrotrophic mires examined, there are wet shifts associated with the decline and local extinction of S. imbricatum, which are dated to cal. ad 1160–1400 (Raeburn Flow and Bell's Flow). In Coom Rigg Moss and Felecia Moss, wet shifts are also associated with the decline and local extinction of S. imbricatum between cal. ad 1395–1485. The decline of S. imbricatum from two other ombrotrophic mires (Bolton Fell Moss Core L and Walton Moss Core 11) is dated to cal. ad 1030–1400, and may have been due to interspecific competition between Sphagnum species during the ‘Early Medieval Warm Period’ and the ‘Little Ice Age’.