Compiled References on the question:
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Anthony Brach Ph.D.
“Does grass produce more oxygen
than trees? I think yes and no.
[What's most] important, in the long run,
is the NETT production
of oxygen – the NETT production of oxygen
in a field of grass is very small,
because the carbon products are not
as long lasting as wood is.”
Jim Tokuhisa, Ph.D.
“Generally, forests have higher primary productivity (and associated O2 production)
What plant [found on land] produces most oxygen?
[answer = aspen trees]
If you want the individual plant that gives off the most oxygen each year, it is probably the 43 hectare (106 acre) network of quaking aspen tree trunks (Populus tremuloides) in Utah that the Guinness Book of World Records lists as the world’s largest living organism. The mass of the quaking aspen is estimated at 6 million kg (6,600 tons). The quaking aspen is considered a single organism because all the stems originate from one root system. There was an article in Discover magazine several years ago on the world record quaking aspen.
Oxygen Production: Trees vs Grass
For natural ecosystems per unit ground area, tropical rain forests generally have the highest annual rates of photosynthesis.
Salisbury, F.B. and Ross, C.W. 1985. Plant Physiology. Belmont, CA: Wadsworth Publishing.
trees vs grass (based on relative surface area and production capabilities of each)
What Makes More OXYGEN: GRASS or TREES?
Anthony Brach Ph.D.
A field of grass might generate more mass of grass in a year than the equivalent
addition of mass in a similar area of forest. It would depend a great deal on the
specific species of grass and forest plants you are trying to compare.
What is more important in the long run is the NETT production of oxygen.
Oxygen is being produced and used up at the same time. What we need to
consider is the overall change. Do we produce more than we use up ( a NETT GAIN) ,
or do we use up more than we produce? (A NETT LOSS)
In order to see a NETT production of oxygen, we must also see a NETT production of
carbon products – noticibly wood. Wood represents the locking up of the Carbon
extracted from CO2 in order to release oxygen. So forests produce lots of wood,
they must also produce lots of oxygen – which is true.
Grass on the other hand produces no wood. Its carbon is turned into carbon products
such as sugars, starches and cellulose. These are all good carbon products, and
represent a production of oxygen, and they are all produced by the forest plants as
The problem is in the next step – what happens to the grass?
If it is left on the ground it rots, and uses up oxygen as the sugars and starches
and cellulose rot and release CO2 again. By equivalence, the forest may lose all
its leaves in fall.
If the grass is eaten by a cow, then the cow uses oxygen to ‘burn’ the grass as
fuel, and produces CO2. Similarly, parts of the forest plants are eaten – fruits
berries leaves etc.
Either way, the NETT production of oxygen in a field of grass is very small,
because the carbon products are not as long lasting as wood is.
This locking up of carbon is a hot topic at the moment, with terms like carbon
banks and carbon sequestering and carbon trading.
By locking carbon up, either in living forests or as underground reserves of CO2,
we are helping to reduce CO2 in the atmosphere, and hopefully reducing the
greenhouse effect which is helping to drive global warming.
Industries which produce a lot of CO2 by burning coal and oil etc, can offset
their emissions by investing in the planting of carbon bank forests. The effectiveness
of this strategy is debated though.
To offset the emissions resulting from the production and burning of 1 gallon of ethanol
(biofuel) you would have to grow approximately 10 pounds of timber – (not including
leaves etc.) To make the offset effective, you have to grow 10 pounds of WOOD for
EVERY gallon of ethanol. That’s a 5000 lb tree for every car every year. If you
keep using petrol or gasoline, the tree has to be even bigger!
original post by:
Nigel Skelton- Tennant Creek
Better Sources of Oxygen for the Planet
While most people learn in school that oxygen comes from plants in the ground, this is only half true. About half of the world’s oxygen comes from phytoplankton, one-celled plants that live in the ocean. More important than producing oxygen, phytoplankton soak up carbon dioxide through photosynthesis. The process allows life in the oceans. Without these little plants we might not have an ecosystem.
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