Current lab members and activities

Understanding tree vulnerability


To understand why dieback is happening now, we need to know exactly when it occurred in the past. Tree rings offer a pathway to answer these questions. Using samples collected over decades, we can date long-dead trees, opening a window to the past. Using an array of tree-ring properties, we aim to reconstruct the history of dieback and identify the external events that lead to outbreaks.


While working to understand the past, we're also working on understanding the vulnerability of trees in the present day. We've deployed a network of sensors in Kosciuszko and Namadgi National Parks that are monitoring diurnal and seasonal variations in growth and moisture status of tree tissues with the goal of identifying the factors that affect infestation of stems by wood-boring beetles.

Identifying and understanding the culprit


Although the damage that leads to dieback is consistent with longicorn (Phoracantha sp.) beetles, the species-level identity of the insect driver of snow-gum dieback remains unclear. Using an array of trapping techniques and experiments, we aim to identify the insect species involved. While interesting in itself, identification of the species is just the start - we need to know when the insects are out and how this corresponds with the vulnerability of the trees they attack. We also need to identify the key factors that determine selection of host trees and survival of larvae.

In addition to the relentless task of checking traps daily and night-time experiments, the entomological aspects of our work involve nigh-time surveys that, as shown below, offer insights to the diversity of Australia's invertebrate diversity

Dating dieback


Previous mapping indicates that outbreaks of snow-gum dieback have occurred on a smaller scale in the Perisher Valley and Ramshead Range. The dead stems left behind provide an opportunity to understand the events that precipitate outbreaks. Systematic sampling of dieback-affected stems during 2021-22 will aim to resolve the precise timing of dieback, in doing so, ideally give us a chance to identify potential causes. This work is being completed by Honours student Michael Jones.

Calibrating tissue water deficit models


The wood-borer genus associated with snow-gum dieback is known to respond to drought stress. Specifically, the larvae of the borer stand a far better chance of surviving in dry bark. As we work towards an understanding pf how bark and wood moisture content affects the insects responsible for snow-gum dieback, we are also working on techniques to generate calibration data for tissue water deficit models. The techniques are varies, drawing upon detailed stem measurements of radial expansion and contraction, sap flow and moisture content, and leaf-level measures of water potential. This work is supported by greenhouse-based experimentation of snow-gum seedlings and is being completed by Honours student Aaron Midson.