Weight of a pine tree

JasonRoland

JasonRoland

Location
White Pines
This question was asked me at lunchtime today by my supervisor- it came to him from a engineer/ lead worker in another department.

"What is the total weight of a dead ( recently dead/ not deteriorating, needles brown but intact) Ponderosa pine tree that is 24" DBH and 100' tall?

The question was for the whole tree, I know there's going to be some variance due to how dead/ dry it is, but am looking for some estimates. I'm sure someone on here has taken one out with a crane?

My SWAG (Scientific Wild A.. Guess) after some calculation was approx 8000 lbs.

Any thoughts?
 
JasonRoland said:
This question was asked me at lunchtime today by my supervisor- it came to him from a engineer/ lead worker in another department.

"What is the total weight of a dead ( recently dead/ not deteriorating, needles brown but intact) Ponderosa pine tree that is 24" DBH and 100' tall?

The question was for the whole tree, I know there's going to be some variance due to how dead/ dry it is, but am looking for some estimates. I'm sure someone on here has taken one out with a crane?

My SWAG (Scientific Wild A.. Guess) after some calculation was approx 8000 lbs.

Any thoughts?
Click to expand...

I have had quite a few people look at a tree and ask me what it weighs. Dead trees are harder to judge, but my system for guessing on green (hardwood) trees is to figure out about how much of the trunk weighs 100 lbs and count up to about halfway. Then double it.
I figure it is close enough for coming up with a guess to bullshit with the customer or the crew. Wouldn't bet my life on it.

Those near-mid ties have shown me that brush is heavier than people might assume, and most branches balance fine if you just tie it in the middle. I figure that it generally works the same way for most trees that don't appear to be shaped strangely.
 
6200 pounds is my guess with not even a picture.

For the trunk weight:

Equation for volume of a cone is V=πr^2*h/3. Here, r=1' and h=100', so V=~103.67 cubic feet
I remembered green Pondo at 45 pounds per cubic foot, but had to look up 28 pounds per cubic foot at 20% moisture content (air dry to 20 percent). Split the difference at 36.5 pounds per cubic foot and you have trunk weight at about 3,800.

For the canopy weight:

Estimate how many yards of material you would expect to chip from the canopy based on previous similar jobs. I have seen Pondos vary enormously from thin canopies in a deep forest to huge canopies when they are solo near a water source. Maybe 6 yards of chips at 400 pounds a yard?

Total: Trunk: 3800 +Canopy: 2400 = 6200 pounds.

Notes:
1. If the trunk at 50 feet is near 1 foot in diameter, a cone is a pretty good approximation for volume of the trunk.
2. Since a yard is about 200 gallons. If you fill up a 50 gallon trashcan with mulch and weigh it and multiply by 4, you have weight per yard.
3. Standing dead trees can still have very high moisture content even in a dry area. I put a moisture meter into a Pondo about this size in Red Feather Lakes, Colorado that had been fire killed 4 years previous and got 55% as the return.
4. Water content makes a huge difference in weight.
 
Thanks for the input. I should point out the method I used to come up with the 8000 weight.
I had considered a "green log chart" as mentioned above, but couldn't find one that accounted for drying weight ( which I understand is subjective, the trees in question are in the fifth year of a drought).
So I found a chart that had weight of dried lumber- but it didn't have Ponderosa Pine. It did have Sugar Pine (Pinus lambertiana) though.
I calculated the tree using volume of a cone, converted it to board feet, multiplied by weight per 1000 board feet off the chart, then rounded up, as I figured that Ponderosa pine is a little heavier than Sugar pine.
That put me at in between 6-7000 pounds ( left my notes at work) then I rounded up to 8000 to account for limb/ needle weight. But I didn't have anything really scientific to base it on.

I was just thinking someone on here with a big crane probably has picked one whole? Or someone with a smaller crane has picked one in a couple picks?
 
Jason,

I find it is simpler to do my calculations with cubic feet weight for estimates than board feet. Here is a good source: http://www.oocities.org/steamgen/woodweights.pdf . I recently removed a similar sized green spruce at about 5000 pounds, but spruce is lighter.

Roger,

I absolutely agree my estimates are based on a taper assumption and lower moisture content. I would guess you did the following calculations to get 4500 pounds: A 30 foot trunk 2 feet in diameter can be approximated by a cylinder : V=πr^2*h =~ 3.14*30 = 94.2 cubic feet. Add some butt swell to round it to 100 cubic feet and multiply by 45 pounds per cubic foot for green pondo.

This is where a picture is worth a thousand words. We could see how much taper and canopy the tree has. Unless it has a monster canopy, I would bet my hat it is less than 10k pounds!
 
I agree that a picture would be worth a lot in this situation. But, the reason there isn't one is because there isn't a specific tree to take a picture of. There are 100 million plus dead Ponderosa pines here in California's Sierras. The "Powers that be" where I work were crunching some numbers, or preparing to crunch some numbers, and this question came up.
The tree in question is an average, dead 6 months-1 year, 24" DBH, 100ft tall tree. Or so I was told.
Thanks to everyone for their input, I'll keep posted if anything comes of it.
 
There is an extensive research literature on allometry of trees for both temperate and tropical zones. Allometry is the allocation of biomass (or energy or other resrources) to various plant parts. Indeed, these started out as models to predict the yield of merchantable lumber. Yes, that is related to weight or biomass but doesn't include foliage, branches, etc. Current modeling approaches are more interested in estimating amounts of fixed carbon, which is closely related to weight of the tree (including the water therein)
For most of the US, the best validated regression models are reviewed in the link: http://www.fs.fed.us/nrs/pubs/jrnl/2014/nrs_2014_chojnacky_001.pdf and these have been pretty-well validated by destructive sampling. No need to go back to approximations for volume equations of a cone. I expect that the OP just wants a round number, but the above article and the references cited therein would get you there. Someone should probably write up a simple guide for common urban and community species and the factors that would result in deviation from the model results. I'll add that to the pile of useful tasks....it might be a while!
 
Hi Jason-

Saw your thread last week and just got busy and forgot to respond.

In Shaver Lake there is a crew working with a big all terrain crane. They are pretty regularly picking trees in 2-3 pieces. They could tell you exactly the number you are looking for. They are doing ponderosa pine, sugar pine, white fir, and probably a few cedars as well. My guess is that you are pretty close with 8k but could be way off depending on the area and how dead the tree is. I'll be up there later this week and can probably get you exact figures.

In Oakhurst, I heard from a reputable source that the loads going to the scale house were coming it at 50% or less of green log chart with certain areas that had been dead a while. Don't quote that as fact until you check it yourself but I have certainly witnessed some incredibly light trees. With the wet weather though they are probably going to get heavier.

One question I have is this: Are the dead pines stronger during the dry season, or during the wet season? My guess is that they are more brittle when dry but that they are stronger. Any other guesses? I would love to do pull testing to failure in different conditions to test my theories.
 
I'd say that they are stronger in the dry season too, but I'm not a big fan of climbing them after they have been standing dead for a while, no matter what season it is. Had a tree yesterday that I had to climb up a ways past where the bark was sluffing off... Never my favorite.

As to the original question, I turned in the 8k estimate and that's the last I have heard of it. Since then we have started and stopped another project, then went to a different place and worked for a few days, then.....
I haven't cut a beetle kill pine tree at my work since I posed the question.
 
To clarify that- I haven't climbed a beetle kill pine tree at my full time (Monday - Thursday, 40 hours) job for a minute, but every side job (Friday-Saturday) I have done for a while has been a standing dead removal.
 
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