[iRock (OP)]

I know 1 mature tree can store 48 lbs CO2 per year and give 260 lbs O2 per tree per year . So exactly how much CO2 1 tree use per year for photosynthesis and storing process or just only 48 lbs ?

I know grassland absorb 2400 – 3600 lbs CO2 per acre per year and create half kilogram O2 per 1 square foot per day . So exactly how much CO2 grassland use per year for photosynthesis and storing process ?

[CliffordK]

It is not quite clear what you are asking.
If you are asking on the globe...  then it is difficult to say.

There are about 57,308,738 square miles on the continents on Earth.
640 acres per square mile.

That gives about: 36,677,592,320 acres, including forests, farmland, deserts, and glaciers.  However, if you say 1 ton of CO₂ per year per acre, then one comes up with 36 gigatons of CO₂ being absorbed on the continents, plus what is absorbed in the oceans. 

However,
All plants are balanced with decomposers.  Even the trees eventually die, and are decomposed. 

So, while about 36 gigatons of CO₂ is absorbed every year, the vast majority is released again by the plants in a cycle. 

Are your numbers off a bit?
The plants and trees absorb Carbon Dioxide (CO₂) + Water (H₂O).

The trees generally store hydrocarbons (chains in the form of CH₃(CH₂)_nCOOH, and various other similar compounds, but mostly carbon and hydrogen).

So, I presume you are saying that they are storing 2400 – 3600 lbs of CARBON per acre, not CO₂.  So, the CO₂ absorbed is about 3 times the value calculated above, or somewhere around 100 gigatons on the continents (with the caveat that most is released again, as mentioned).

[alancalverd]

Even the trees eventually die, and are decomposed.

which makes one wonder why coal looks like dead trees. Or indeed why Venice hasn't disappeared.

Fact is that the historic record shows very rapid rises in atmospheric CO2, each followed by a slow drift downwards. Now given the propensity of trees to grow rather slowly, the curve suggests that plant sequestration is quite a longterm effect, with a halflife of several thousand years.   

[yor_on]

That's a tricky one. And myself I think it is educated guessing mostly as it seems a new field.

http://earthobservatory.nasa.gov/Newsroom/view.php?id=21354
and
http://www.enn.com/ecosystems/article/45308

And it's also about diversity, of fauna and flora. Like different types of trees sequestering CO2. Pine trees are as good a leaf trees there as I get it, but you won't see the same biodiversity. It's like using space mapping, stating that there is as much trees growing as we cut down. It doesn't tell us a thing about the biodiversity, without knowing what types of (fast growing) trees they plant, also knowing what grew (existed) there before.

[alancalverd]

Hardly new science. This was the substance of my first biology lesson, in 1956.

"Plants use sunlight to synthesise complex organic molecules from atmospheric carbon dioxide, with water, nitrogen compounds and trace elements principally taken up from the soil. Animals get energy from the oxidation of carbohydrates and hydrocarbons, mostly from plants."

[yor_on]

photosynthesis ain't new, but I think that discussing carbon sequestering, giving defined numbers for different environments, are rather new, to me at least.

[alancalverd]

I can't think why. The entire farming and forestry industries are based on quantified CO2 sequestration by photosynthesis. What the customers do with the product is another matter, of course, but if you can't calculate the mass of cabbage or construction timber you can grow in a year, you won't be able to raise capital or loans to run your agribusiness!

[yor_on]

You got a good point there Alan. It's more of looking at it another way I guess, and different trees should sequester carbon differently. Like some Forrest industry cutting down old forests with slow growing trees, having 'tight year rings', then planting other, fast growing ones, to get their new investments back as fast as possible. What that will mean in form of sequestering carbon? Maybe not as much? As they will continue to plant that variety, after thinning the woods out of grown trees again. I don't know there? It's a tricky business.
=

There is one thing though, the faster growing woods will make bad planks (bending) and so furniture, if I remember right. So there might be a higher probability that it will be used as fuel?

[CliffordK]

The older trees are still putting on some wood.
Consider a tree, 3" in diameter, and 10 feet tall, perhaps with 1/4" growth rings.
Vs a tree that is 4' in diameter, 12' in circumference.  100 foot tall, with 1/32" growth rings.  The big old tree may still be putting on quite a bit of wood.

Of course, you might have more little trees in a clearcut than big trees in an old growth or climax forest.

[alancalverd]

It's more of looking at it another way I guess, and different trees should sequester carbon differently.

I think foresters know this.
 

There is one thing though, the faster growing woods will make bad planks (bending) and so furniture, if I remember right. So there might be a higher probability that it will be used as fuel?

Again, carpenters and energy suppliers do specify their materials quite carefully. Trunk oak makes great furniture, churches and ships, but is very difficult (and expensive) to turn into fuel pellets. Birch ply is a lot stiffer than single grain softwood, so makes excellent cheap furniture and lightweight aeroplane parts. Very fast growing softwood makes adequately rigid chipboard and fibreboard, or indeed fuel.

[yor_on]

I don't think it is that simple Alan, to know how this sequestering works practically. Saw this one just now   http://www.eci.ox.ac.uk/news/articles/2013/1024plantecology.php   about 'ecosystem dynamics of Amazonian and Andean forests.' And maybe take a look at http://scitechdaily.com/shedding-light-on-the-role-of-forests-in-carbon-sequestration/   first, as it is forests we discuss.

And then we have marine biological organisms, as plankton and their shells. We also have all sorts of seaweed etc in the oceans. And it all comes together into one world interacting with itself and space. Don't think we have any perfect models for all this.

[alancalverd]

No need for comprehensive models. The original question was about trees consuming CO2. All the carbon in a tree comes from the atmosphere, and foresters know exactly what gain in dry weight to expect from any particular species at any stage in its development, so the answer is known. The subsidiary question of how long does that carbon remain sequestered depends entirely on what you do with the tree: anything from minutes in the case of biofuel to millions of years in the case of mined coal deposits, or for ever if you don't mine the coal.

What interests Joe Public nowadays is the re-release of plant carbon by animals. When the temperature rises, insects and other coldblooded creatures become more active and exhale CO2 derived from plant material. Hence the observed historic (and current) variation of CO2 concentration with temperature.     

[yor_on]

That may be Alan, assuming one know all parameters regarding a tree, its speed of growth, soil, sun, rain, humidity, and whatever else that may come into play? But I don't think we have those figures on a individual basis normally, outside of a lab environment? I would expect generalizations, estimates based on statistics when people discuss it. Climate science is on the whole fairly new I think, even though we understand the role of photosynthesis.
=

As for the last comment, would you have a link to what you're referring?
=

Found a description of how to calculate amount of CO2 sequestered in a tree, per year.
http://www.broward.org/NaturalResources/ClimateChange/Documents/Calculating%20CO2%20Sequestration%20by%20Trees.pdf

Now, they seem to agree with me, but then also with you

[fries]

Hi, I have a question.  I was wondering what reputable source found that mature grasslands sequester 2400-3600lb of C/acre per year?  Also, are there any sources that give estimates on other land types and their average rates of carbon sequestration per (hectare, acre, etc..) per year? 

There are lots of studies about their potential ability to store, but I am looking for what different land types sequester naturally.  I recognize the potential for variability, but was hopeful to find some roughly, average, estimated data.

Thank you

[Bored chemist]

Did nobody look at the numbers?
"I know 1 mature tree can store 48 lbs CO2 per year and give 260 lbs O2 per tree per year "
The big problem there is that 260 is bigger than 48.

If I said I took 48 pounds of ore and extracted 260 pounds of metal from it, would anyone take me seriously?

[alancalverd]

There's a difference between turnover and surplus in any business.

Quite a lot of carbon goes into making seeds, leaves and twigs which fall off (expenditure) leaving a little to be sequestered as trunk growth (reinvested profit) and a fair quantity of oxygen (tax!). A mature private company may not worry too much about reinvestment as long as the workers, shareholders and tax man are happy with their take. 

[Bored chemist]

48 lbs of CO2 only contains 35 lbs of oxygen. The other 13lbs is carbon and roughly speaking that will create about 32.5 lbs of timber (calculated as cellulose).
Two things can happen to that timber. It can be incorporated into the tree, or it can be lost.
If it's lost as leaves then they decay and take up the equivalent amount of oxygen anyway.

Where does the rest of this magical O2 come from?

[yor_on]

You're perfectly correct, I definitely missed to check his numbers and taken together they make no sense to me either. I'll blame it on me being to lazy to convert it into meaningful numbers, as kg, for me. But the pdf gives a estimate in the same eh, indecipherable terminology. I now looked at lbs and found it to be a pound? 0.453592 kg.

So what he suggest is that  "1 mature tree can store 21,772416 kg CO2 per year and give 118 kg O2 per tree per year," right?

The first number seems to come from  "A single mature tree can absorb carbon dioxide at a rate of 48 lbs./year and release enough oxygen back into the atmosphere to support 2 human beings."

- McAliney, Mike. Arguments for Land Conservation: Documentation and Information Sources for Land Resources Protection, Trust for Public Land, Sacramento, CA, December, 1993

How correct that is? Depends on what tree, I would guess? and the soil, and the weather locally. Then we have using kg:s O2, instead of using liters? One kg oxygen is about 700 liter so converting it to liter that will make 118 x 700 = 82600 liter oxygen if I got it right.

And then there is the question of what a weight means here, the dry weight of a tree is what's used in the pdf and that is apparently about 72.5 times its weigh, growing in its natural 'wet' state. To get to the carbon content you multiply that dry weight (in kg:s, please) by 50% and there kg seems a good choice too.

But the first number seems plausible, the second? 82600 liter per tree, per year, right? Divide with 365 and we get... 226.3 liters per day.... (all depending on if I'm doing the conversions correctly here:). So, how much oxygen is produced by one tree, per day? I don't know really? It's a complicated question it seems. Take a look here http://wiki.answers.com/Q/How_much_oxygen_does_one_tree_produce

Ok, but how much would a average human consume per day then? That one seems possible to answer.

"Somewhere between 500-600 liters of oxygen (at 1 atm pressure) a day. That may sound like a lot, but there are only 1.42 grams of oxygen/liter at 0C, 1ATM. So that's only 710-852g/day. Or, a pound and a half to just under two pounds/day." is one answer

So assuming that the first statement is correct, and one tree is able to sustain oxygen for two persons, per year, then assuming that those use between 1000 to 1200 liters oxygen per day, then one mature tree should produce the same amount, possibly?

And I'm getting a headache

Arrggh.
1100 liters x 365 = 401500 liters per year.. doesn't add up to me?

(And I definitely lost myself, doing all those conversions)
==

Ok, found the other statement too.

"On average, one tree produces nearly 260 pounds of oxygen each year. Two mature trees can provide enough oxygen for a family of four." 

- Environment Canada, Canada's national environmental agency

Ah well..

[CliffordK]

Did nobody look at the numbers?
"I know 1 mature tree can store 48 lbs CO2 per year and give 260 lbs O2 per tree per year "
The big problem there is that 260 is bigger than 48.

See my first reply.

I assume the author meant that the tree stores about 48 pounds of carbon.
And releases 260 lbs of oxygen. 

Don't forget that the equation is:
CO₂ + H₂O --> Hydrocarbons + Carbohydrates + Oxygen, however you choose to balance it.  Perhaps that is still off a bit.

But, it is about 3 oxygen atoms (AW 16) released for every carbon atom (AW 12) incorporated into pure hydrocarbons.  A bit less oxygen released for carbon incorporated into cellulose.
Hmm, with the 3:1 ratio, one still gets: 3*16*48/12 = 192    (48lbs Carbon incorporated ==> 192lbs Oxygen released).

How thick is a typical growth ring on a mature tree?  I suppose a lot of it depends on the tree.  A Douglas Fir, Juniper, or Bristlecone Pine have quite different growth characteristics.  Even the definition of a "Mature" tree is ambiguous, and would also depend on whether it is in a dense forest, or isolated.

For a "Mature" Doug Fir:
Consider 1/32" growth rings.
Let's consider a cone,
4' at the base, 100' tall. 
Surface area of a bottomless cone is
πrs, with s the length of side.
So we get about 628 square feet of new growth, or about 20 cubic feet (for 1/32" growth rings).
About 30 lbs per cubic foot density (dry?)
And, it comes up with about 600 lbs new growth a year (trunk wood). 

I suppose we're somewhere in the ballpark.

It might be a bit higher if you're calculating for a Sequoia or Redwood.  A bit less for a mature bristlecone pine or juniper tree.

[alancalverd]

If it's lost as leaves then they decay and take up the equivalent amount of oxygen anyway.

Not true. Most decay is anerobic (the sludge at the bottom of the leaf pile). Conversion of plant material to CO2 is mostly done by larger animals: this is called life on earth, and is the fault of god, not the tree.