8. A Different Approach to Site Evaluation and Some Preliminary Results

Abstract

SYNOPSIS This paper describes a new approach towards site evaluation of exotic tree species which have a limited and non-representative occurrence. Instead of applying the classical site factor analysis and measuring a considerable number of sample plots of different ages at different sites, six experiments were laid out under selected and controlled conditions. Because temperature and soil depth are the major factors affecting tree growth when there is little variation in rainfall, three localities were defined varying widely in temperature at altitudes of 1 200 m, 1 400 m and 1 600 m. At each locality a site with a deep soil and one with a shallow soil were selected for parallel experiments. Each of these consisted of four replications of 25 trees of 11 Eucalyptus species and Acacia mearnsii. The design, lay-out and establishment of these experiments are described as well as results up to two years. In addition to growth performance many meaningful facts about frost resistance, cold tolerance, sensitivity to insects and pests, soil depth and drainage requirements and drought resistance became evident even at this early stage. An important finding was that when all growth factors are adequate, the growth rates of most species are similar (parallel) irrespective of what the rates were previously.