Relationship between height growth of Scots pine (Pinus sylvestris L.) and site factors in Great Britain

The rate of height growth in Scots pine stands throughout Great Britain was examined in relation to site factors. The site factors included measures of geographical variation, topography, soil chemical and physical variables at two levels, several measures of soil phosphorus status, foliar monoterpenes and estimates of mean values of climatic variables. Principal component analysis was used to make an initial selection of regressor variables from 88 site factors for use in multiple regression equations. A dependent variable was obtained by removing the effect of age on height. The dependence of this expression on site variables was then examined using step-up multiple regression, starting with the selection of regressor variables made by the principal component analysis (P.C.A.), then adding transformations and interaction terms until 69% of variation was significantly accounted for over Great Britain, and up to 99% for parts of the country. Simpler equations using only those regressor variables which could be read from maps were also calculated.Variations in growth over Great Britain are associated mainly with solar radiation, soil texture and soil moisture content. For separate parts of the country the solar radiation term disappears from regression equations.