The role of climate variability on regeneration success of Eucalypts in southeast Australia

Associate Professor Craig Nitschke
University of Melbourne

Using records on seedling establishment this project sought to understand the influence of past climate variability on the regeneration success of key Eucalyptus species in southeast Australia.

The researchers found the influence of climate varied by regeneration type (occurrence vs. abundance) and forest type. For the occurrence of regeneration, climate and topography played significant roles in the occurrence of recruitment for all forest types. For Alpine Ash (AAS) climate was dominant. The most consistent predictor for regeneration success/ failure was Annual Heat Moisture Index (AHMI) which is a measure of aridity. AHMI had a significant negative effect suggesting that as aridity increases the probability of regeneration failure increases. Mean annual temperature (MAT) was a significant factor in Mountain Ash (MAS), AAS, and Mountain Mixed Species (MMS); however the impact varied by forest type. In AAS increasing MAT led to failures in recruitment while in MAS and MMS, warmer MAT facilitated an increase in recruitment success provided conditions are not too arid. Easterly aspect was the most consistent topographical variable with negative effects on MAS and AAS suggesting areas with a westerly aspect were more likely to fail. Elevation for MAS and MMS had a positive effect.

Elevation was not correlated strongly with MAT within each forest type so was included in the model and as such it may be acting as proxy for another climate variable or edaphic variable such as soil depth and or soil texture. For MMS, steep sites were also more likely to fail.

This study will provide knowledge for being able to predict the impact of future climate change on spatial and temporal patterns of eucalyptus regeneration.

against potential bushfires coming from westerly or northerly directions. Eight working bees tackled weedy threats to the woodlands, selectively removing wheel cactus, Paterson’s curse, horehound and African boxthorn. Bush Heritage ecologists set up a series of monitoring sites at yellow and grey box communities to track tree health and condition with the view to develop intervention strategies. Analysis of data collected will give a clear picture of the overall health of vegetation types and the bird populations
they support. Early indicators from the project suggest health of box eucalypt species is of concern.