The question is quite simple. Where do trees get all their weight? I know that trees take in lots of water and nutrients from the surrounding soil, but when a very large tree is cut down and the wood is allowed to dry over the period of a year or two, the wood is still very heavy. So, did all of this weight come out of the ground? If it did, does the ground that trees grow on slowly sink due to the trees sucking out all of the nutrients? It would take a hell of a lot of soil/nutrients to equal the weight of a large tree. Matter cannot be created or destroyed (unless you’re a physicist) so all this weight came from somewhere…
It’s magic!
Actually the question is not that simple as it has to do with the entire plant physiology of tree cell growth, nutrient uptake, etc etc etc. Wood is heavy because it contains a fair amount of water (even when “dry”) and cell wall structures of varying densities which bind water and the below mentioned “extractives”.
In general things are often heavier than you think.
Britannica yields.
http://www.britannica.com/bcom/eb/article/5/0,5716,119325+1+110435,00.html?query=wood%20densities
Wood properties
Density and specific gravity
Density is the weight or mass of a unit volume of wood, and specific gravity is the ratio of the density of wood to that of water. In the metric system, density and specific gravity are numerically identical; e.g., the average density of the wood of Douglas fir is 0.45 grams per cubic centimetre (28 pounds per cubic foot) and its specific gravity 0.45, because one cubic centimetre of water weighs one gram. The density of wood varies from about 0.1 to 1.2 grams per cubic centimetre (specific gravity 0.1 to 1.2). Differences between species and among samples of the same species are attributable to different proportions of wood substance, void volume (volume of cell lumens and wall spaces), and the content of extractives. The amount of extractives in wood varies from less than 3 percent to more than 30 percent of the oven-dry weight. It is obvious that the presence of these materials, located to a large extent within the cell wall, can have a major effect upon the density.
Determination of the density of wood in relation to that of other materials is difficult because wood is hygroscopic, and both its weight and volume are greatly influenced by moisture content. In order to obtain comparable figures, weight and volume are determined at specified moisture contents. The standards are oven-dry weight (practically zero moisture content) and either oven-dry or green volume (moisture content above fibre saturation point, which averages about 30 percent).
Most mechanical properties of wood are closely correlated to density and specific gravity. It is possible to learn more about the nature of a wood sample by determining its specific gravity than by any other simple measurement.
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Contents of this article:
Introduction
Structure of wood
General xylem structure and cell types
Earlywood and latewood
Sapwood and heartwood
Transverse, radial, and tangential sections
Cell types
Structural variations and defects
Ultrastructure and chemical composition
Wood properties
Density and specific gravity
Hygroscopicity
Shrinkage and swelling
Mechanical properties
Thermal properties
Electrical properties
Acoustic properties
Harvesting the wood crop
Wood utilization
Roundwood products
Sawn wood
Drying
Preservation
Veneer
Plywood and laminated constructions
Particle board
Fibreboard
Pulp and paper
Other products
Mechanically derived products
Chemically derived products
Bibliography
From the air.
Wood is mainly water and carbon. Plants “breathe” carbon dioxide and release oxygen. Do the math.
A lot of the weight comes out of thin air. Tree takes in
CO2 and outputs oxygen. It keeps the carbon. Cellulose, which is pretty much what trees are made out of, is pretty much carbon and hydrogen and oxygen which you can get from
water.
It strikes me that this question suggests a very effective approach to educating people on the importance of trees in removing atmospheric carbon dioxide.
Take a person to a big tree. Ask them the question in the OP. Then explain that the tree’s weight comes, in large part, from carbon drawn out of the atmosphere, and that each growth ring in the tree represents more carbon being removed.
Cut the tree down, and it obviously stops removing carbon. Burn the tree, and it actually releases the carbon back into the atmosphere.
Pretty straightforward and easily comprehensible explanation of why deforestation is a bad thing.
This question reminds me of when I worked at Biosphere 2. As the apparatus operated under far higher concentrations of CO[SUB]2[/SUB] than the atmosphere currently has many people assumed it would just make plants grow better and have no adverse effects. All the effects in the carbon cycle weren’t known and the best way I heard it put was that Bio2’s atmosphere was the equivalent of force feeding donuts to all the plants. The most obvious effect on trees of the artificial atmosphere was from lack of wind. Trees grew with plenty of mass but without the stress of wind they didn’t grow strong enough to stand without support.
Sadly the apparatus is no longer operated as a sealed environment. Much of it is open to the public and the last time I was there the human habitat portion was a Volvo exhibit.
That reminds me of a story I saw about an ongoing research project at Duke. They were exposing certain sectors of the Duke Forest to high levels of carbon dioxide to see what effects that would have on plant growth or otherwise. I haven’t seen the results.
The answer is actually quite simple. Trees get their weight from gravity.
Perhaps you meant, where do trees get their MASS?
Wasn’t there some foul up (not yours I’m sure- "Damn that Padeye he’s killed us all!) in the design where IIRC CO2 was not being efficiently removed from the air and they were suffering from oxygen deprivation.
Yeah didn’t the oceanic portion nearly die and the beetles overrun the ‘apparatus’ and the rainforest die out, or something?
–Tim