Moorland vegetation history and climate change on the North York Moors during the last 2000 years
A history of vegetation and climate change during the last two millennia is elucidated from ombrogenous blanket peat sequences from the central and eastern North York Moors. The evidence is derived from five mires Harwood Dale Bog, May Moss, Fen Bogs, Yarlsey Moss and Bluewath Beck. May Moss received particular attention because it is the only remaining unmodified blanket mire on the North York Moors. All the sites were cored, with May Moss yielding seven cores, four of which were extruded along a five metres transect. The cores were selectively analysed for plant macrofossil, testate amoebae, humification and pollen. Chronologies were constructed using 14C dating and the judicious use of biostratigraphic marker horizons. Comparison of 14C dates obtained on bulk peat samples and on pure Sphagnum remains encountered substantial differences, which raises anxieties about 14C dating of a material as heterogeneous as peat. The regional vegetation history elucidated from the pollen evidence reflects changes in the demography, culture, economy and climate of the North York Moors. Evidence of woodland decline and abundant agricultural taxa are attributed to phases of increased agricultural exploitation of the uplands in response to a commercial approach to farming during the Romano-British period, population expansion during the Anglo-Scandinavian period, and attempts to exploit the moorlands during the boom periods of the 12th-13th and 15th-16th centuries. Conversely, phases of woodland expansion and agricultural decline are associated with the Roman withdrawal from England, the 'harrying of the north' in AD 1069-70 and demographic collapse during the 14th century. T estate amoebae, plant macrofossil and humification stratigraphies provide a record of mire palaeohydrology, which is used to infer a history of effective precipitation. There is a broad consistency within the palaeohydrological indications from a single core, which indicates that the techniques support each other. Furthermore, similar testate amoebae, plant macrofossil and humification stratigraphies were encountered in adjacent cores at May Moss. There is evidence of pronounced shifts to wetter/cooler conditions circa 500 BC, AD 450, 850, 1400, 1625 and 1825 separated by unambiguously drier/warmer phases circa AD 200-450, 700-800, 1100-1200, 1550-1600 and 1750-1800. The palaeoclimate time series displays a strong correlation with the record of solar variability; however, biosphere, atmosphere and oceanic interactions in the North Atlantic region and global volcanism also affect regional climate.