Mid-Holocene environmental change at Black Ridge Brook, Dartmoor, SW England: A new appraisal based on fungal spore analysis

Black Ridge Brook is an upland peat site in a high rainfall area of SW England. Pollen evidence has shown that it was once wooded, with Betula and Corylus dominant, before periods of change to more open ground and the spread of mire vegetation. Previous palaeoecological work at the site inferred a history of burning based on microscopic charcoal levels, with the burning periods reducing Betula cover. These changes occurred between 9000 and 6300 BP (radiocarbon years) during the Mesolithic archaeological period, and have been linked to the impacts of hunter-gatherers using fire, as suggested elsewhere in upland Britain. In this paper, hypotheses of deliberate burning, grazing and the reasons for using fire are tested using non-pollen palynomorphs in addition to the microcharcoal and pollen data. While indicators of dung are present, the frequencies are low, and not always in the levels expected on the basis of vegetation change, although some correlation of disturbance indicators is seen in the earlier Holocene before woodland cover reached a maximum. There is evidence for increased and sustained growth of Corylus following increases in inferred fire frequency. Statistical analysis of the combined data set shows the association of some non-pollen types with specific stages in the development, and then recession, of woodland. Other types show the presence of on-site burning or host plants, and help distinguish between local and regional vegetation changes. The nature of the depositional environment is both shown by, but also affects, the non-pollen microfossil record.