Mistletoes increasing in ‘undisturbed’ forest: a symptom of forest decline caused by unnatural exclusion of fire?

Summary

Increases in populations of mistletoes were observed in undisturbed eucalypt forest near Eden, New South Wales. Repeated counts in an ecological research area showed that there were large increases in mistletoes over 13 years. Populations of mistletoes quadrupled in areas that had few or no prescribed burns. Mistletoes doubled in areas that were patchily burnt by fires of generally low intensity six times in 13 years, but this increase was not statistically significant. Hypotheses advanced to explain the perceived proliferation of mistletoes in rural lands cannot account for the increases in undisturbed forests. However, the results of this study are consistent with a general hypothesis of tree decline in rural lands and forests caused by chronic abiotic stress. Unnatural exclusion of low intensity fire may impair the health of eucalypt forests and cause outbreaks of pests, pathogens and parasites. Populations of mistletoes or other parasites could readily be monitored as indicators of ecological imbalance.

Keywords:

• mistletoe
• eucalypt
• undisturbed forest
• forest decline
• fire regimes