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  1. #1
    Join Date
    Dec 2010
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    Mornington Peninsula
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    Default Tree Diameter Question

    Hi All,

    Hopefully this is the correct forum to ask this simple question, if not Mods please move as required.

    I have a very, very small timber lot. Circa 18 years old.

    The question is, is there a way to increase the girth of the trunk? I am not particularly interested in the height of the tree, just the diameter for slabbing (eventually) purposes. The trees are Bluegums and a non-descript Eucalyptus.

    TIA

    George

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  3. #2
    Join Date
    Feb 2006
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    Perth
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    Default

    It's going to take decades but if you thin out some of the trees they will grow less tall and then are more likely to put those resources into gain in girth.

  4. #3
    Join Date
    Sep 2010
    Location
    Port Sorell, Tasmania
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    Default

    I will qualify any of my comments by saying that the majority of my forestry experience was in native forest management and not so much in plantations so these comments may not be totally accurate.
    As Bob said, thinning. Bluegums at 18 years of age, I suspect, are already fairly tall in which case thinning can lead to wind damage (trees blowing over or snapping off). If the trees are on the Mornington Peninsular then you are probably in a windy location. We considered thinning of pines was risky when they were over 18 metres tall. To height a tree simply position yourself (level with the base of the tree) so you can line up the top of a tree by looking up at an angle of 45 degrees. Distance from where you are standing to the base of the tree, plus your height, will give you tree height.
    For maximum diameter in bluegums, we considered a density of 150 to 180 stems per hectare is somewhere around the mark. Thats around 8 metres between trees. If you have a density substantially higher than that thinning is likely to be risky. Then there is the issue of falling the trees to be removed without damaging the retained stems.
    That's created more questions than answers I suspect.
    Tony
    You can't use up creativity. The more you use, the more you have. ~Oscar Wilde

  5. #4
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    Dec 2010
    Location
    Mornington Peninsula
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    Default

    Thanks Tony,

    The trees are planted on a 4 x 4 mtr grid and some of the Bluegums are at the 600mm BHD. Without checking, I would estimate ~18 mtr height.

    Looks as if, I am stuck with what I have, and let nature take its course....

    George

  6. #5
    Join Date
    Apr 2000
    Location
    Australia
    Posts
    201

    Default

    George, yes, you make an important point. I grow Red Cedar here on my farm and it is not the log length I'm interested in but log diameter. It is the wide boards that are worth the money and not the long boards. My suggestion would be to consider an open grown tree as this is the maximum diameter growth you can get and consider how by thinning out your forest you can approach something like that bearing in mind certain limitations such as wind damage. On my farm, I had an open grown Gympie Messmate that in about 90 years had gotten to a diameter of about 5 feet. I also have a Red Cedar in a semi open situation that has grown from about 6 inches in diameter to about 20 inches now and that is on a butt log of about 8 feet and a large spreading crown. You can also bear in mind that an overstocked forest is unhealthy as each individual tree lacks vigor and as they cast their branches, they don't have enough growth to grow over the branch scare and allow destructive decay to enter.

  7. #6
    Join Date
    Apr 2006
    Location
    Hobart
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    3,320

    Default

    Hi George

    I have never worked with blue gum, but years ago, as an economist, I did a lot of work with plantation kamarere (E deglupta); I hope that experience is relevant.

    FIRST; trees grow towards light; if they have lots of light they grow shorter and fatter, if they have to struggle for light they grow taller and thinner.
    SECOND; essentially trees suck nutrients out of the soil, work some chemical magic, and convert them into wood fibre, aka growth. When the roots of a tree meet the roots of another tree then they start competing for those finite nutrients and growth slows.
    COMBINING the above two arguments, if you thin then you should reduce root nutrient competition and enhance growth rates on the remaining trees and the enhance light should result in a higher proportion of that growth being in girth rather than height.
    THE RISK, as Tony says, is from damage during thinning and wind damage later. Your site may affect this risk - wind exposure, ease of access for thinning, etc.

    ONE option might be to leave a wind break, and thin the rest?


    Cheers

    Graeme

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