Competition in Mixed Stands of Pinus radiata and Eucalyptus obliqua

Abstract

1. Relative growth rate, mortality and stem form of individual trees in mixed stands of planted P. radiata and naturally regenerated E. obliqua over 5 years were examined in relation to their sizes and the density and leaf area index of their neighbours. 2. Relative growth rate increased with tree size and decreased with increasing neighbourhood leaf area index for both species, but it increased with increasing neighbourhood density as a result of a release from competition due to mortality in the neighbourhood. 3. Mortality affected smaller E. obliqua. The probability of death decreased with increasing tree size. 4. Height to diameter ratio, an indicator of stem form, decreased with tree size and increased with neighbourhood leaf area index for both species. 5. The growth, mortality and changes in stem form of individual trees led to changes in density-dependent stand level characteristics such as mean height to diameter ratio and size distribution patterns.