Some months ago I received a note from a forester about dieback in native Australian forests, following is an edited version:
“There is a very large and growing forest health issue particularly in the dryer forest types. Die back known by a variety of names from Bell Bird Dieback to Mundulla yellows is affecting thousands of hectares of native forest and appears to have the potential to affect thousands more.
It is a little talked about issue but it covers all land tenures public forest and national park and private property.
Based on observation by forest managers an hypothesis has been put forward that dieback is the result of changed fire regimes. In particular reduced incidence of low intensity burns has promoted changes in soil chemistry and moisture levels that have promoted antagonistic conditions to over storey eucalypts resulting in dieback and ecological change. Parallels can be drawn with the US Pacific North West and the forest health problems being documented there after 70 years of fire exclusion as a result of the overly successful ‘Smokey the bear’ campaign.”
This morning I received a note from David Ward. The following has been edited slightly:
“There is an article (Jay Withgott ‘Fighting Sudden Oak Death with Fire?’, Science Aug 2004 Vol.305 p.1101) which decribes how California oaks are dying from Phytophthora ramorum.
Two researchers (Moritz & Odion,’Prescribed Fire & Natural Disturbance’, Science Dec 2004, Vol. 306, p.1680) have found that there is some association between this pathogen and long fire exclusion. The researchers caution that there is not yet a demonstrated causal relationship, and that prescribed fire may have a different effect from natural fire. However, the article may be of interest to Australian researchers, and land owners.
… Some local WA Nyoongar Elders have said that, in their view, traditional summer burning, on dry soil, prevented the fungal diseases which we see now. At the same time, summer burning promoted other fungi, some of which were good tucker.”
This afternoon, Vic Jurskis send me a copy of his recent paper titled ‘Eucalypt decline in Australia, and general concept of tree decline and dieback’, Forest Ecology and Management, Volume 215 (205) pages 1-20 (available online at www.sciencedirect.com for $30).
The paper includes the following comments under a heading ‘Implications for Management’:
“Considerable resources are being devoted to research of contributing factors in tree decline but
few corrective actions are being applied in eucalypt forests other than quarantine and hygiene measures to restrict the spread of Phytophthora .… Prescribed burning appears to be the only silvicultural practice that can have widespread application in conservation reserves and
timber producing forests. Passive management of nature reserves in Australia has failed to maintain healthy ecosystems, especially in the case of the grassy forests that were most depleted by clearing for
agriculture and are now mostly declining in health and changing in structure.To conserve healthy dry and moist eucalypt forests it will be necessary to restore more natural outputs of nitrogen and moisture by using frequent low intensity fire and/or grazing. Ecological burning
regimes should be integrated with hazard reduction burning to protect forest health as well as social and economic values.”
David Ward also commented that it would be “valuable to get views from other parts of Australia on this topic”.
Jennifer Marohasy BSc PhD has worked in industry and government. She is currently researching a novel technique for long-range weather forecasting funded by the B. Macfie Family Foundation.