By Dr Joe Harvey-Jones, Tree Farmer
Why is it the right time for these fine trees to be felled?
There is an argument to say that allowing these quandongs to dominate the stand for so long has been a mistake. Should more of them have been removed earlier in a 'thin to waste' process, to give other species a chance?
As a faster-growing species, quandong are clearly dominating the stand on my farm, suppressing other species, which will eventually lead to growth stagnation of the whole stand.
If left there, the large quandongs will put on a little more girth for a while, until the site reaches its capacity.
If left for another ten years, we may be able to harvest a little more timber, but it will be limited to these fast-growers, which in the end, will likely be sold for lower prices than the more valuable species that are currently suppressed.
Furthermore, many of the suppressed saplings will perish as they try to compete for dwindling sources of light and nutrients.
If you imagine the quandongs removed, it becomes clear that increased light and nutrients will go to the remaining stand. The beauty of these mixed stands, in my opinion, is that a new 'winner' will emerge among the species present. We can then stand back and observe (and in my view – accept!) this natural process.
There will be no need to 'pick winners', no need to thin more than necessary; just let them all compete and may the best tree/species win!
This is what happens in the natural rainforest. ‘Gap Theory’ tells us that as large trees reach maturity and crash to the forest floor, a sun-filled gap in the canopy is created. The increased light levels in the gap stimulate seedlings and saplings in the understory to race for the light. The losers eventually die back. The decaying giant meanwhile, returns nutrients to the soil, to feed growth resulting from the new light energy.
Note:- We may grumble about recovery rates from sawn logs being around 40%, but the offcuts and trash returned to the forest help feed the growth cycle. I am personally wary of schemes to utilise or 'value-add' by finding off site uses for thinnings and trash – eg. bio-energy. Such an approach of removal offsite, is tantamount to mining the soil of nutrients, on which future growth depends.
In summary I think my 'hands-off' approach to pruning and thinning (mainly due to lethargy) has not been overly harmful…
Giving the fast-growing quandongs freedom to grow has:-
- Forced the slower species to self-prune, as they chase the dwindling daylight under the ever ascending quandong canopy, and;
- Improved the chances of reasonable returns from this first thinning harvest.
I am also convinced by now that any strategy I can come up with, is unlikely to be as good as one taken from nature – a lesson I have learned over many years around the farm.
[Most of my costly interventions with eg. weed infestations would, in hindsight, have been best left on the drawing board].
I am looking forward to seeing which species in my mix will be the next to take off and win the race for light and nutrients.
However, given the benefit of hindsight, there are many aspects of my plantings that could have been done better….
In my next article, I will be examining how I could have designed the woodlot better from the start, in terms of:-
- Ground preparation,
- Species mix,
- Species layout, and;
- Tree spacing.
It was great to have Rowan Reid here as part of his Master Tree Growers Prep Course recently. His insights into how to plan a woodlot, and then manage it, were invaluable.
Pretests of Harvest Methodology
In mid-January 2018, the first harvest began in earnest at my Eureka property.
There had been a couple of rehearsals leading up to the main event…
Some of you came to the Harvest Brainstorm event at Eureka in October last year, designed to gather knowledge from experts in harvesting and processing. As growers, we needed to educate ourselves in the art and science of felling trees safely, and processing them to produce high grade timber.
Two easily accessible trees were felled in advance of the day, and milled onsite as a demonstration for the participants to comment on.
An interesting exercise completed around that time, was to explore the idea of crown reduction, to limit damage to the remaining stand during selective felling. In the photo you can see Eddie from the Lundesang team on his way up to remove the larger side branches on one of my biggest quandongs.
The added cost per tree of this approach we estimated to be about AUD$150, but remember that the cost remains the same whatever the tree size.
So the decision making process takes into account:
- The weight of the crown and its potential to do damage,
- The volume of timber and its value (the pictured tree yielded around 0.8 cubic metres of sawn timber), versus;
- Potential future losses from damage to the surrounding trees when felling with intact crowns.
Partly for financial reasons, and partly because of the advanced felling abilities of the team working at my place, I have subsequently opted to cop the damage from felling intact trees:-
- Collateral damage has been acceptable to date, and;
- The high density of the planting means there are more than enough survivors to carry on.
A Test Harvest of Two Large Quandongs
In December, Karl Vikstrom from Lundesang helped me to mark two large quandongs for felling and sawing. Our experience with these would help create confidence in our approach for the full harvest to be undertaken early in 2018.
In general, the January harvest proved to follow the pattern established in this pretest, so the reporting which follows can be taken to be similar to subsequent activities.
Winching and Snigging
The tractor with winch attachment used for snigging was provided by Lundesang. The tractor is seen here with the winch rope diverted at 90° via a pulley. The tractor and driver are in a safe position 20 metres away from the line of fall.
Meanwhile at the tree, a throw bag and line are prepared, to take the winch rope as high as possible up the trunk.
In practised hands, the throw bag will after an attempt or two, arc over a high branch, and back down to the ground. The weighted bag is removed and the twine end spliced to the winch rope end. The winch rope is hauled up hand over hand and down again, to be secured high up on the trunk
Making the Cuts
Once the main line is hauled into place round the trunk, the saw cuts can commence. The front cut is made in a wedge shape on the the trunk. (In the photo, note that the buttresses distort the apparent depth of cut, which although too deep, is almost within the tolerance range. With the safety of a winch rope in place, the cut depth is probably less critical).
Also note the trimming of side buttresses, to avoid issues of insufficient chainsaw bar length. It also will avoid complications that can occur if the hinge travels into the buttress areas, which are likely to be different on each side of the tree – leading to twisting motions as the tree falls (eg, the hinge parting on one side well before the other side cracks).
With the front cut complete, a signal is sent to the tractor operator, via an intermediary, to take the strain (careful attention to how much pressure to apply is important here!).
The back cut is then made at a height of around 50mm or more above the apex of the front cut. You can just see the chainsaw blade commencing the cut.
In this situation (winch rope attached and tensioned), the back cut was not taken to the point where the tree commenced to fall by gravity. The back cut was stopped short, to leave a larger than normal hinge, and the tractor operator advised to take more strain. Thus the direction of fall is decided by the winch rope, laid along a pre-determined path.
If the winch had not been available, other strategies are brought into play. Where there is any doubt about the weight distribution of the tree, the back cut is commenced until the bar is far enough in for wedges to be inserted. As the cut is deepened, the wedges are hammered in behind the advancing blade. Once in place, they prevent any risk of the weight of the tree falling backwards and trapping the blade. Hammered further in, they begin to move the centre of gravity towards the desired fall direction. There is a margin for error in fall direction with these strategies, so wherever possible, a winch system is to be recommended.
The decision not to invest in crown reduction was noted earlier, and is supported by the picture below which shows the minimal damage resulting from felling one of the two trees described above.
One tree was demolished in the fall, the other debarked by the snigged trunk. However, with many trees and saplings surviving in the vicinity, the loss was insignificant to the future wellbeing of the stand.
Cutting the Log into Millable Lengths
With two trees on the ground (the other being to one referred to earlier with the crown reduction) the logs were snigged out onto the road, where Eddie cut them into sections.
Decisions around where to cut a log are normally made at the saw site, based on curvature, observed faults and thoughts about the end-use of the timber.
In this case, we intended to mill offsite, in part to compare the economics with onsite milling, so the length of the crane-truck bed was also an issue.
Loading the Logs for Transport to the Mill
Milling operations will be covered in an upcoming article – I will need to get some expert co-writers to help, as milling is not in my everyday skill-set!
Nor, by the way is felling, so please send me comments on the article or phone me for a chat on 02 6688 4257.