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Could the sum of the thicknesses of the side branches somehow be related to the 'plumbing' requirements of a tree? I.e., below the branching point, there are vessels of a total cross section of X, and above the branching point, there are vessels with a total cross section of Y. There must be some optimal X:Y ratio. On Thu, May 19, 2016 at 1:13 AM, Stephen Shaw <srshaw@dal.ca> wrote: > If the unpointy top bit at 75' had an effective diameter even of only 6" (0.5'), the frustrum-of-a-cone volume would go up quite a bit more to 84.4 cu ft and the weight up to 2868 lb, or 1.43 US (short) tons. Very weighty. > > I gave up trying on the web to find out the predicted volume of a white (?) spruce's branches and leaves, given the known dimensions of the trunk, though I'm sure it's out there. There are lots of formulae for estimating trunk volume, but most foresters are concerned with harvestable trunk wood and not with branches/leaves, which as we know in these parts are now mostly biomassacred. > > This did turn up an interesting and widely confirmed observation though, made by Leonardo da Vinci as to why trees aren't overly top-heavy and so don't simply splinter under the weight of their own branches: he had noticed that the total thickness of branches at a particular height in a tree is equal to the thickness of the parent trunk at that height -- a still-believed approximation even in use by graphics illustrators to draw supposedly realistic branching trees, but still lacking a clear physical explanation. > There's an associated formula and possible modern explanation for Leonardo's rule, stemming (sic) from a tree's need to limit the effect of excessive wind shear summed on the canopy leaves, at > http://www.wired.com/2011/11/branching-tree-physics/ > > Steve (Hfx) > ________________________________________ > From: naturens-owner@chebucto.ns.ca [naturens-owner@chebucto.ns.ca] on behalf of pce@accesswave.ca [pce@accesswave.ca] > Sent: Wednesday, May 18, 2016 7:06 PM > To: naturens@chebucto.ns.ca > Subject: [NatureNS] A weighty tree > > A storm a few years ago brought down a big spruce in the forest behind > our house. In falling, the tree bumped up against, and landed on, > various other neighbouring trees, pressing some of them flat and causing > others to lean at odd angles. > > I was wondering just how much a big tree like that might weigh, so today > I went out and measured it. > > The broken-off part (above the stump) is about 75' long (forgive the > Imperial measure), and the circumference at the base of the broken-off > part is 5'7". Modelling the stem as a cone, that gives a volume of 60.6 > cubic feet. Using a typical density for green (i.e. not dried) spruce of > 34 lb/cubic foot, I get a weight of the stem alone of slightly over 2000 > lb., or one ton. > > Of course the branches and needles would add more weight, but I don't > have a good figure for that. It would depend upon just how bushy the > tree was. I'd be happy to say somewhere around 500 pounds, though. > > A big tree! > > Peter Payzant > Waverley
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