Comparisons of spatial pattern,structure, and tree composition between virgin and cut-over jarrah forest in Western Australia

Several old growth (unlogged) and regrowth (logged) stands in the northern jarrah forest of Western Australia were studied in respect of spatial pattern of tree species, segregation between tree species, distribution of trees of each species by diameter class, and tree species composition. The species are Eucalyptus marginata and Eucalyptus calophylla (overstorey) and Banksia grandis, Allocasuarina fraseriana, Persoonia longifolia and Persoonia elliptica (understorey).Most populations of the species are aggregated at small but random at large scale. This pattern probably originates from non-random seed fall. Eucalyptus marginata and B. grandis are segregated, probably for the same reason. Manipulative experiments showed that interspecific competition does not prevent establishment of B. grandis seedlings. On a local scale, heterogeneity in several surface soil properties does not help explain spatial patterns.The diameter-class distributions indicate that regeneration of all species occurs irregularly. This probably results directly from the release of dormant advance growth following temporary reduction in overwood competition induced by disturbance such as wildfire or logging. Banksia grandis is not a rare or scattered component of old growth jarrah forest. A single logging of jarrah trees does not necessarily alter the density or diameter class distribution of B. grandis.