Understanding biological factors associated with Eucalypt dieback in the ACT

Dr Jasmyn Lynch
University of Canberra

This project integrated field data on biotic variables into landscape-level statistical analyses of the biophysical factors influencing dieback in Box Gum woodland in the ACT. The biotic variables include condition of trees in relation to broad land use type; presence/absence of Psyllid parasites and mistletoes on Eucalypt  trees; regeneration, epicormic  regrowth and defoliation of  Eucalypts; and distributional records of                                        associated threatened fauna (e.g. Superb Parrot, Polytelisswainsonii). 

The research shows that despite recent positive change in the condition of Box Gum woodland in peri-urban/rural areas, overall there is a decline in the ecological community. A large number of trees have declined between 2004 and 2017. Different generalized land use classes appear to have an association with tree canopy condition, although with the broad coverage of the three classes over the ACT, other factors such as habitat and current climate might be influencing the outcome. Field observations indicate that Yellow Box is showing greater resilience than Blakely’s Red Gum, due to more observations of regeneration and advanced epidermic growth. Although no evidence was found of an association with Psyllids and there were insufficient data to analyse the influence of mistletoe, some bird species appear to significantly overlap in distribution with habitat clusters of differing mean accumulated condition or overall change in condition. However, the current analysis is not able to determine if the significant differences in condition are a result of positive/negative effects of the species abundance levels or if the species are selecting habitat with trees of particular canopy condition.