Competition in mixed stands of Pinus radiata and Eucalyptus obliqua.
Abstract
Relative growth rate, mortality and stem form in individual trees in mixed stands of P. radiata (planted in 1975 on a former native forest land) and naturally regenerated E. obliqua, in Mount Cole State Forest, Victoria, Australia, were examined in 1985 and 1990, in relation to the sizes, density and leaf area index of neighbouring trees. 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 release from competition due to mortality in the neighbourhood. Mortality affected smaller trees of E. obliqua, with the probability of death decreasing with increasing tree size. Height to diameter ratio, an indicator of stem form, decreased with tree size and increased with neighbourhood leaf area index for both species. 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.