Using national yield tables as a basis, the growth of Scots pine Pinus sylvestris L., Lodgepole pine Pinus contorta Douglas ex Loud., Norway spruce Picea abies (L.) Karst. and Sitka spruce Picea sitchensis (Bong.) Carr. have been compared. From the trends of height growth with age and the levels of total volume production the paper attempts to relate the differences in growth in the various countries climatic factors. In the first part broad comparisons are made between the climatic types in Britain with those of Northern Europe and N.W. America and certain aspects such as growing season length, accumulated temperature, frost-free season, day-length and availability of water are high-lighted. Forest trees differ biologically from low-growing vegetation in growth response to climatic factors and as only one of the four species is native to Britain the yield tables considered may be based on different genotypes. In the second part the productivity of each species is examined separately and tentative conclusions are offered for the observed differences, which may be very large. Part of this variation may be due directly to climatic effects or climatic/genotype interactions, largely appearing as a latitudinal cline with increased growth at lower latitudes and/or as better growth under the longer growing season of maritime climates. The rest (varying with species) is attributed to differences between provenances, soil factors, stocking or silvicultural treatment. In general forest productivity in Britain is shown to compare very favourably with that in N. Europe and N.W. America. © 1979.
