Because cutting down trees for farming and firewood has been such a pervasive land use, restoring the depleted tree populations in grassy woodland has been an important restoration activity, one which people are crucially aware of. Less well understood is the importance of dead and fallen timber in the ecosystem. Two pieces below discuss this issue:
Coarse woody debris – leave it alone
Have you stopped harvesting dead trees yet? – if not, just stop now
While there is recognition of the role of fire in the evolution of Australian vegetation, much of the tradition lore about managed burning in southern Australia has been lost. The final piece on this page is entitled:
The Burning Question – the use of fire to improve grassland condition
Coarse woody debris – July 2012
The very ugly expression that headlines this contribution is actually a technical term for one of the most important parts of our local ecosystems. An alternative name is certainly badly needed and, fortunately, ecological terminology is not cast in stone. But before we get mired in such detail, I’d like to explain what this debris is, and why it is important.
Coarse woody debris is the cast-off branches and fallen trunks of the trees in our forests and woodlands. So it is coarse (as in coarser than twigs and leaves), it is woody (fairly obviously), but whether it is debris or not is highly debatable. Fallen timber is one means by which nutrients and carbon are re-cycled into the soil. In the process, it provides food and shelter for a wide array of plants and animals. Bacteria, fungi and soil critters cause wood to rot and progressively feed larger invertebrates such as spiders, beetles and centipedes. These in turn provide food for native mammals and birds. Termites make their living by chewing away on wood and in turn provide all the sustenance our echidnas need. And the progressive hollowing out of the branches and the spaces beneath the logs form shelters for all sorts of things – insects, lizards, birds, possums – everyone except us. Even ground plants can benefit from the fallen timber. It provides shelter from desiccation and grazing, and high quality soils from the nutrients and organic matter released by the rotting wood. So in terms of quality habitat for wildlife, wooded areas with mature trees (which have hollows and tend to shed more branches) and lots of … coarse woody debris … rate very, very highly.
Now is the time of year that the hills ring with the sound of chainsaws, bringing in the firewood that warms our houses and provides one of the great pastimes of a rural existence – the caveman’s telly. And because most of us care about our environment a common refrain of home firewood collectors is “I don’t cut down trees, I just take the fallen branches and logs”.
My response is noooooooooooooooo!
Don’t pick up the fallen timber or saw up the hollow logs for firewood.
There is a more ecologically sound way to achieve a warm house in winter.
This involves cutting live trees, and so does not seem quite the right thing, but read on.
Many of us have dense stands of young trees on our properties. If you do not now, you may one day have, as this unusually wet season has produced an enormous flush of eucalypt regeneration. The trees you are looking to harvest are small – a trunk diameter of less than 40 cm. They are growing close together, with the branches held high on the trunk. The crowns of the trees touching or overlapping. These features indicate that there are more trees competing for the space than will survive in the long term and typically this happens in regrowth forest. Mentally compare the size of these trees with the crown diameter of a full-sized eucalypt. Over time a dense stand of trees will thin itself as the stronger trees mature and slowly dominate, while the weak trees die. If the trees are evenly matched, this self-thinning process can take a lifetime.
Some human-initiated thinning of these pole sized trees can speed up growth of remaining trees and still retain the forest structure – plus you get some firewood. An average spacing of 6 m x 6 m will leave plenty of trees. Other patterns of tree thinning could include small clearings within a dense stand to allow a mature tree to breathe or just to allow understorey plants to grow. Clearings can improve habitat quality by creating variation in the forest structure and these spaces within a forest can also have aesthetic appeal. Note that in fire risk areas, the 50 m management zone around the house needs to be treated differently. Here, the tree crowns should not be touching, so a woodland structure with well-spaced trees is indicated, with leaf litter and fallen timber cleared up.
Remember we are talking about non-commercial harvesting of firewood. You need to consult the state regulations and work within them in order to be able to sell the timber.
In my view, cutting young green trees is a much more environmentally sound way of obtaining firewood than cutting mature trees or sawing up fallen or dead standing timber. Sure, you have to wait a couple of years for the wood to cure, but if you are not yet converted to the cause, picture the experience of someone I know, chain sawing though an innocent family of Blue-tongue Lizards sheltering in the hollow of the fallen log designated as firewood.
Hopefully, you are now convinced that coarse woody debris is a misnomer, and names like ‘woody treasure’, ‘finest organic matter’, ‘habitat helper’ and ‘nature’s gift’ are running though your mind. Personally, I intend to stick with the name ‘fallen timber’ for now. Whatever it is, it is definitely woody and definitely not debris.
Have you stopped harvesting dead trees yet? – May 2015
It’s been nearly three years since I touted the wonders of “coarse woody debris”, or fallen timber as I prefer to call it. I argued for its protection on the grounds of the marvellous habitat it provides for lots of lovely fauna.
With the cool weather coming, no doubt many of you are turning your mind to the comforting wood fires of winter. Those already-seasoned dropped limbs and large logs that are lying invitingly on the forest floor are hard to resist.
So I am just checking whether you have broken your bad habits yet? Have you learned to turn your back on this woody treasure in favour of thinning some young green timber from the dense stands that abound in our district?
If I was unable to convince you before, maybe I can re-state the case, as well as provide further compelling arguments.
First, food. Fallen limbs and trees provide sustenance to fungi and bacteria, which in turn feed an array of invertebrates, which then provide for bats, reptiles, echidnas, birds and mammals. In other words, they are at the base of an important food web. More directly they provide physical shelter for bats, echidnas and mammals.
Some of you will have noted that logs also provide some shelter for rabbits and foxes. This is an unfortunate side-effect, but without logs, rabbits and foxes would still exist, while most native fauna would not.
There are some other important, but more subtle effects of log recycling. These have been revealed through studies of the environment around decaying logs. This includes work that has been part of the experiment at Mulligans Flat and Goorooyarroo Nature Reserves in which woodlands were provided with logs to replace those that had been removed for firewood in the past.
These logs were sourced from eucalypts cut from street plantings in Canberra. It was found that small lizards and beetles proliferated around the freshly-placed logs after only a few years. The logs provide habitat for them by protecting them from trampling and grazing.
Similarly, within a few years of dying, decaying logs provide carbon and essential nutrients (nitrogen and phosphorus) to the soil. They protect the immediate environment from sun and wind, and thus keep the surrounding soil cooler and moister. This no doubt an attraction for the beetles and lizards at certain times, but it also promotes the growth of plants, particularly those fond of productive environments. In certain settings this may promote the growth of weeds, an unfortunate but relatively minor setback in the face of the other positive aspects of logs.
On Gang Gang, we have used logs widely and successfully in the treatment of erosion. We lay logs and branches along the contour of a slope, at right angles to the directions in which water would flow downhill. On eroding soil, any establishing plant helps, including some weeds.
As well as contributing all those goodies to the soil, these logs slow down the water flowing over the soil, and enable the accumulation and lodging of seeds and organic matter that further encourages plant establishment. It is a cheap, locally available resource, especially useful for the treatment of sheet erosion..
Where the logs are large, or there are attached branches, there is the added feature of some protection from grazing animals. This can give plants, especially grazing-sensitive plants, an opportunity to flower and produce seed, whereas in the open they may be more easily sought and readily grazed off.
By providing islands of soil fertility and niches for plant establishment, logs are a vital link in the restoration of woodland and forest. They can assist soil health, ecosystems processes and increase the diversity of plants and animals.
The Burning Question – May 2017
By all accounts there used to be a great deal of burning undertaken by indigenous Australians. They used fire to promote fresh growth in the grasslands and make them more appealing to herbivores such as kangaroos, wallabies. They also used fire to assist with the flushing and capture of this game, and for ease of movement through the bush. More subtle use of fire was employed to improve the habitat in which various edible animals and food plants could flourish. The early explorers with their eye to settlement and farm production were tremendously impressed by the quality of the soil, and the richness and diversity of the grasslands that the aborigines maintained.
In southern Australia, the orally-transmitted knowledge behind these burning practices is largely gone. Displacement was rapid, and very few of the early European settlers were interested or respectful enough to sit down and learn why the aborigines did what they did with fire. Europeans had other plans in mind. Their herds of livestock, ploughs and agricultural seeds were going to transplant a different kind of food production onto the landscape. What need was there for fires when the sheep and cattle were going to use the grass?
For an ecologist such as myself, there is a great longing to have seen these pre-European landscapes and have an understanding of the management practices of the time. Could it help us regain the large healthy populations of Yam Daisies and other corm-producing plants that once fed some many people yet remained abundant? Is it possible that traditional management practises could rehabilitate some of the many species of wildflower that are now rare?
Historians such as Steven Pyne and Bill Gammage have helped us to understand how profound and deliberate the aboriginal use of fire was. Their accounts provide tantalising glimpses of attitudes and the practises of burning, but little that is systematic or instructional, and which can be applied confidently now. Trying to translate these random observations into a coherent view of the entire complex landscape is like peering through pinpricks in a dark shroud. Tiny glimpses and so many unanswered questions. How were the requirements of the many hundred different plants and animals met? How frequent were the fires and under what seasonal and weather conditions were they lit? Directing and controlling the course of a fire in bare feet, would call for an astonishing level of skill.
If enough people has been asked and the books written, the knowledge would be priceless. Of course they would not be able to directly provide an operating manual, as so much has changed between then and now. Think of it:
– our soils are more eroded from heavy grazing but may have more nutrients from fertilizers;
– our grasslands have been grazed but rarely burnt for most of two centuries;
– there are many non-native species present;
– there is infrastructure that should not be burned, buildings, fences, contained livestock;
– we are not used to handling fire anymore and regard it as a danger and a health hazard. These are some of the reasons we are taking baby steps when it comes to using fire to foster diversity and health in the local vegetation. Though if we did have access to aboriginal fire lore, there might have been some guiding hands to lend confidence to our first tottering attempts.
At Gang Gang we started burning small areas a few years ago, our own first steps. Which is why we spent Easter sending up plumes of smoke, visible to friends across the valley. We are necessarily more encumbered than our aboriginal forebears, with water sprayers and shovels in hand. Still, this does not disturb the meditative process of watching gentle flames trickle across the ground. And when a contained circle of grassland flares up with a low roar and settles with a sigh, it is deeply satisfying. Perhaps we are genetically pre-disposed to having a firestick in our hands.
 Pyne, S.J. 1991. Burning Bush: A Fire History of Australia. Henry Holt, New York.
 Gammage, B. 2011. The biggest Estate on Earth: How Aborigines made Australia. Allen & Unwin, Sydney.