Saturday, November 14, 2009

Bush Fire Aftermath

It's been about ten weeks now since bush fires ravaged the countryside around us. We had only a glimpse of the damage that had been done before we left for the USA. As we headed out for our long roundabout trip to Sydney airport back in August we were confronted by the smoking remnants of the fire that had burnt through the Meroo National Park right on our doorstep.
However on our return we had time to absorb the enormity of the desolation. Thousands of hectares of state forest, national park and private property had been devastated. The two major fires had burnt from the mountains to the west of us to the beach. It was only luck and the skill of the Rural Fire Service that protected dwellings and prevented any loss of life.
In the forests just the gum trees, the eucalypts, have been left standing. The entire understorey is gone. In the coastal heath there is nothing. Just blackened sticks.
But Australia is the driest continent on earth with a high incidence of fire so many plant species have adapted to this over the millenniums.
Take Eucalypts for instance. Many species possess lignotubers. These are a woody swelling at the base of the stem which contain buds and food reserves. They develop new shoots rapidly after fire. The lignotubers are usually accompanied by epicormic buds located within the bark which cause the familiar sight of red shoots springing from a blackened trunk.
We are beginning to see this!
Many species however don't have this feature and rely on bark thickness or a heat reflective or absorbent bark to resist fire. However an intense fire will often kill these species. But the death of the tree accelerates seed shed and those together with that shed in the years before, and kept dormant by low light, will suddenly spring to life. This is a result of the enhanced nutrition of the seed bed and the reduced canopy shading, both caused by the fire.
Lignotubers are also evident in many shrubs and small trees of the Proteaceae eg. Banksia sp., Casuarinaceae and Leguminosae to name a few. But unfortunately the majority of understorey plants in our region will have to rely on seed regeneration.
Banksia ericifolia for instance are killed outright by fire and the recovery of the species depends on the accelerated seed shed a fire induces. It has been found that seeds are released earlier and quicker from cones exposed to high fire temperature. If the fire is followed by periods of good rainfall, a very large proportion of seed will germinate. So while we have had some rain and there is some evidence of ground cover regeneration activity, we will need a lot more to see the forest return to its previous condition.
From other areas near us that have been fire devastated in the past, it seems that it takes about five years for the bush to return to "normal" with the only evidence of fire being random blackened tree trunks under the green/blue canopy of leaves.

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