THE PREDICTION AND DISTRIBUTION OF GENERAL YIELD CLASSES OF SITKA SPRUCE IN SCOTLAND BY EMPIRICAL-ANALYSIS OF SITE FACTORS USING A GEOGRAPHIC INFORMATION-SYSTEM

A framework has been developed to predict growth of Sitka spruce (Pice a sitchensis (Bong.) Carr.) at a regional scale throughout Scotland ba sed on an analysis of yield, site, and climatic factors. Using the gen eral yield class (GYC) system for predicting forest production (m(3) h a(-1).year(-1)), the statistical model was integrated with a geographi c information system to predict tree growth at a resolution of 1 km(2) Site factor data from 487 sample sites were analysed along with the a ssociated climate data derived from monthly 30-year means recorded at meteorological stations throughout the country. Multiple regression wa s used to develop and validate the model, which accounted for 59% of t he variation in observed GYC. Standard errors of prediction were deter mined by analysis of variance to provide confidence limits for the 1-k m(2) GYC predictions. The distribution of these estimates of productio n was plotted in the form of a digital map for Scotland, housed within the geographic information system and providing a facility to readily analyse and summarise regional information.