Dendroclimatology of Pinus sylvestris L. in the British Isles
A study of the properties of tree-ring density and ring-width chronologies from five sites in the British Isles, two in Sweden and two sub-fossil sites in Northern Ireland is described. The technique of x-ray densitometry is used to measure density. It is shown that it is possible to use x-ray densitometry on well preserved sub-fossil pine. Chronologies have been constructed for parameters of earlywood and latewood widths, ring-width, maximum and minimum densities for all sites. The statistical properties of chronologies are related to the latitude and altitude of the sites. Sub-fossil chronologies behave differently to any of the living tree chronologies. Response functions on monthly temperature and precipitation data are calculated for the five tree-ring parameters for the living tree chronologies. A principal component analysis involving 25 ring-width chronologies from northwestern Europe is used to examine the spatial relationship between British and European ring-width chronologies. The continuous pattern of density variation across the annual ring is measured for trees from two scottish sites, at Glen Derry and Glen Affric from 1900 to 1979. A method of constructing and comparing annual density profiles by fitting cubic spline functions to the density data is described. This has enabled the effects of growing season climate on density to be examined. The importance of temperature in governing tree-ring density is demonstrated. The use of image analysis techniques to measure the continuous variation in cell dimensions across the annual ring is described. Variations in ring density are explained in terms of changes in wall thickness and lumen diameter. A comprehensive literature review on the physiological mechanisms controlling the response of tree-ring width and density in P. sylvestris to climate is described. The physiological causes-for the climate-growth response in earlywood and latewood widths and densities are summarised seperately. It has been possible to explain some of the results of the response function analysis and the density profile study in terms of physiological processes.