THE CLIMATIC HISTORY OF PINE IN THE CAIRNGORMS BASED ON RADIOCARBON-DATES AND STABLE ISOTOPE ANALYSIS, WITH AN ACCOUNT OF THE EVENTS LEADING UP TO ITS COLONIZATION

The Cairngorm Mountains in Northeast Scotland [UK] display abundant evidence for glaciation and ice-wastage. At the end of the Weichsel (Devensian) the deposits and open water became colonized by plants. The vegetational succession is briefly described, with particular reference to the establishment of pine before 7300 B.P. It is pointed out that macrofossils provide a much more trustworthy basis for investigating the history of Pinus sylvestris in the area. The nature of the macrofossils is described and their age discussed on the basis of the forty 14C dates obtained. These 14C age determinations form a framework for understanding the climatic history of the region. Cellulose from the wood-remains was investigated using the new technique of deuterium (.delta.D) isotope analysis. The principles of this stable isotope analysis are explained and a relationship to precipitation proposed. These measurements indicate changes in the amount of precipitation in the course of the last eight thousand years. Excessively low .delta.D values are considered to be related to periods with very heavy rainfall. Such "pluvial" phases are now known to have occurred at about 7300 B.P. between 6200 B.P. and 5800 B.P., from 4200 B.P. until 3940 B.P. and about 3300 B.P. The presence of pine-stumps above the recent tree-line is mainly related to preservation, i.e. suitable climatic conditions for their envelopment by the blanket bog vegetation. Peat accumulation started at about 6000 B.P. as a result of a marked increase in precipitation and underwent rejuvenation at about 4200 B.P. This explains why the bulk of the stumps are referred to this period. No pines younger than 3200 B.P. have been found above 530 m. A climatic rather than a human cause is suggested for this decline.