Structure and composition of a mixed-species eucalypt forest in south-eastern Australia

Context In a changing world, it is critical to establish large-scale, long-term monitoring of forest communities and populations. The Forest Global Observatory (ForestGEO) coordinates a global network of such plots, but it lacks any plots in Australia. Aims To establish a large-scale, long-term forest monitoring plot in species-rich lowland eucalypt forests in south-eastern Australia. Methods A 16-ha (400 × 400 m) permanent forest dynamics plot was established in a lowland mixed-species eucalypt forest near McMahons Creek, Victoria, Australia. All free-standing trees with diameter at breast height (DBH) ≥1 cm were mapped, measured, and identified to species. Key results The census recorded 51,195 individual trees from 46 species and was notable for high congeneric diversity. Eucalyptus species represented 96.4% of total basal area and 98.8% of aboveground biomass, but only 18.9% of individuals. Mean aboveground biomass was 385.9 Mg ha−1 (range: 336.4–490.6 Mg ha−1). Large trees (DBH ≥61.5 cm) occurred on ~75% of the 400 (20 × 20 m) quadrats. Topography and fire history influenced stem density. Mid-slopes and ridges were dominated by Eucalyptus sieberi regrowth, likely resulting from selective logging in 1961–62 and from the 1983 Ash Wednesday fire. Conclusion The census revealed complex patterns in forest structure not previously described in mixed-species eucalypt forests, highlighting the dominance and species richness of Eucalyptus and the importance of these forests as terrestrial carbon stores. Implications The plot is the largest, most detailed forest monitoring plot in Australia and, with time, will provide insights into stand development patterns and long-term impacts of disturbance and climate change.