Carbon Dioxide is Plant Food?

[I AM NOT THAT GUY 5,715]

Summary

• The potential for elevated [CO2]-induced changes to plant carbon © storage,

through modifications in plant production and allocation of C among plant pools,

is an important source of uncertainty when predicting future forest function. Utilizing

10 yr of data from the Duke free-air CO2 enrichment site, we evaluated the

dynamics and distribution of plant C.

• Discrepancy between heights measured for this study and previously calculated

heights required revision of earlier allometrically based biomass determinations,

resulting in higher (up to 50%) estimates of standing biomass and net primary productivity

than previous assessments.

• Generally, elevated [CO2] caused sustained increases in plant biomass production

and in standing C, but did not affect the partitioning of C among plant biomass

pools. Spatial variation in net primary productivity and its [CO2]-induced

enhancement was controlled primarily by N availability, with the difference

between precipitation and potential evapotranspiration explaining most interannual

variability. Consequently, [CO2]-induced net primary productivity enhancement

ranged from 22 to 30% in different plots and years.

• Through quantifying the effects of nutrient and water availability on the forest

productivity response to elevated [CO2], we show that net primary productivity

enhancement by elevated [CO2] is not uniform, but rather highly dependent on

the availability of other growth resources.

http://face.env.duke.edu/PDF/np185-10.pdf

[Ali G. 37]

Unfortunately, we are not plants. Not to mention, we are cutting down forests faster than slim loads his guns.

[Niels Bohr 72]

CO2 is also poisonous to plants if they're inundated with it. It goes both ways. Good and bad.

[I AM NOT THAT GUY 5,715]

CO2 is also poisonous to plants if they're inundated with it. It goes both ways. Good and bad.

Interesting part of the study, was that this was an "open air" CO₂ enriched forest. They noted in similar studies in "closed system" studies, that the same level of increased biomass was not noted. When further analysis was done, it was determined that the entire scope of nutrients would have to be included in the study. Since increased amounts of carbon dioxide accelerate grown, then there also must be a ready supply of nitrogen, water, and trace elements, something not accounted for in the "closed system" experimental results, that underestimated carbon sequestration by as much as 50%.

In essence, it is not the CO₂ is "poisonous" to plants, or to humans either, but in sufficient concentrations, it can displace nitrogen, in the case of plants, and oxygen, in the case of humans, the same way the gas can be used to smother a fire. But with an 80% approx of the atmosphere being nitrogen, then it would be unlikely even doubling or tripling the concentration of carbon dioxide in the atmosphere would reach that level.

Edited March 9, 2010 by Lone Ranger

[one...two...tree 2,762]

Summary

• The potential for elevated [CO2]-induced changes to plant carbon © storage,

through modifications in plant production and allocation of C among plant pools,

is an important source of uncertainty when predicting future forest function. Utilizing

10 yr of data from the Duke free-air CO2 enrichment site, we evaluated the

dynamics and distribution of plant C.

• Discrepancy between heights measured for this study and previously calculated

heights required revision of earlier allometrically based biomass determinations,

resulting in higher (up to 50%) estimates of standing biomass and net primary productivity

than previous assessments.

• Generally, elevated [CO2] caused sustained increases in plant biomass production

and in standing C, but did not affect the partitioning of C among plant biomass

pools. Spatial variation in net primary productivity and its [CO2]-induced

enhancement was controlled primarily by N availability, with the difference

between precipitation and potential evapotranspiration explaining most interannual

variability. Consequently, [CO2]-induced net primary productivity enhancement

ranged from 22 to 30% in different plots and years.

• Through quantifying the effects of nutrient and water availability on the forest

productivity response to elevated [CO2], we show that net primary productivity

enhancement by elevated [CO2] is not uniform, but rather highly dependent on

the availability of other growth resources.

http://face.env.duke.edu/PDF/np185-10.pdf

How much CO2 in the atmosphere is used by plant life, Bill? Do you know? Is it measurable? Is that variable factored into projections?

[I AM NOT THAT GUY 5,715]

How much CO2 in the atmosphere is used by plant life, Bill? Do you know? Is it measurable? Is that variable factored into projections?

Don't know, but it can be estimated, although this study would suggested it is being underestimated by a third in the current projections.

[one...two...tree 2,762]

Don't know, but it can be estimated, although this study would suggested it is being underestimated by a third in the current projections.

Actually, here's what the study showed:

It has sometimes been argued that the earth’s biosphere (in large part, the terrestrial biosphere) may have the capacity to sequestor much of the increased carbon dioxide (CO2) in the atmosphere associated with human fossil fuel burning. This effect is known as “CO2 fertilization” because, in the envisioned scenario, higher ambient CO2 concentrations in the atmosphere literally “fertilize” plant growth. Because plants in turn, in the process of photosynthesis, convert CO2 into oxygen, it is thus sometimes argued that such “co2 fertilization” could potentially provide a strong negative feedback on changing CO2 concentrations.

Recent experiments and model calculations, however, suggest that this is unlikely to be the case. A set of controlled experiments known as FACE (“Free Air CO2 Enrichment”) experiments have been performed in which ambient CO2 levels are elevated in forest stands and changes in various measures of productivity are made over several years. Experiments of this sort that have been done at Duke Forest indicate (in agreement with models), that any elevation of productivity is likely to be short-lived and is unlikely to significantly offset any gradual, long-term increases in co2 due to human activity. This is due in part to the fact that other conditions (e.g. availability of nutrients such as Nitrogen and Phosphorus) appear to quickly become limiting, even when carbon availability is removed as a constraint on plant growth when ambient CO2 concentrations are sufficiently increased.

A few simple calculations indicate that any hypothesized co2 fertilization response is unlikely to offset a significant fraction of projected increases in atmospheric co2 concentration over the next century. At present, about 600 billion tons of carbon are tied up in the above-ground vegetation. About 2-3 times this much is tied up in roots and below ground carbon, which is a more difficult carbon pool to augment. By comparison, scenarios for fossil fuel emissions for the 21st century range from about 600 billion tons (if we can keep total global emissions at current levels) to over 2500 billion tons if the world increases its reliance on combustion of coal as economic growth and population increase dramatically. These numbers clearly indicate that sequestering a significant fraction of projected emissions in vegetation is likely to be very difficult, especially as forests are cleared to make way for agriculture and communities. While there are possibilities of storage in wells and deep in the ocean, stabilizing the atmospheric CO2 concentration would require gathering up the equivalent of 1 to 2 times the world’s existing above ground vegetation and putting it down abandoned oil wells or deep in the ocean. While CO2 fertilization could help to increase above ground vegetation a bit, storing more than a few tens of percent of the existing carbon would be quite surprising, and this is likely to be more like a few percent of global carbon emissions projected for the 21st century.

http://www.ghgonline.org/co2sinkplants.htm

[I AM NOT THAT GUY 5,715]

Actually, here's what the study showed:

It has sometimes been argued that the earth’s biosphere (in large part, the terrestrial biosphere) may have the capacity to sequestor much of the increased carbon dioxide (CO2) in the atmosphere associated with human fossil fuel burning. This effect is known as “CO2 fertilization” because, in the envisioned scenario, higher ambient CO2 concentrations in the atmosphere literally “fertilize” plant growth. Because plants in turn, in the process of photosynthesis, convert CO2 into oxygen, it is thus sometimes argued that such “co2 fertilization” could potentially provide a strong negative feedback on changing CO2 concentrations.

Recent experiments and model calculations, however, suggest that this is unlikely to be the case. A set of controlled experiments known as FACE (“Free Air CO2 Enrichment”) experiments have been performed in which ambient CO2 levels are elevated in forest stands and changes in various measures of productivity are made over several years. Experiments of this sort that have been done at Duke Forest indicate (in agreement with models), that any elevation of productivity is likely to be short-lived and is unlikely to significantly offset any gradual, long-term increases in co2 due to human activity. This is due in part to the fact that other conditions (e.g. availability of nutrients such as Nitrogen and Phosphorus) appear to quickly become limiting, even when carbon availability is removed as a constraint on plant growth when ambient CO2 concentrations are sufficiently increased.

A few simple calculations indicate that any hypothesized co2 fertilization response is unlikely to offset a significant fraction of projected increases in atmospheric co2 concentration over the next century. At present, about 600 billion tons of carbon are tied up in the above-ground vegetation. About 2-3 times this much is tied up in roots and below ground carbon, which is a more difficult carbon pool to augment. By comparison, scenarios for fossil fuel emissions for the 21st century range from about 600 billion tons (if we can keep total global emissions at current levels) to over 2500 billion tons if the world increases its reliance on combustion of coal as economic growth and population increase dramatically. These numbers clearly indicate that sequestering a significant fraction of projected emissions in vegetation is likely to be very difficult, especially as forests are cleared to make way for agriculture and communities. While there are possibilities of storage in wells and deep in the ocean, stabilizing the atmospheric CO2 concentration would require gathering up the equivalent of 1 to 2 times the world’s existing above ground vegetation and putting it down abandoned oil wells or deep in the ocean. While CO2 fertilization could help to increase above ground vegetation a bit, storing more than a few tens of percent of the existing carbon would be quite surprising, and this is likely to be more like a few percent of global carbon emissions projected for the 21st century.

http://www.ghgonline.org/co2sinkplants.htm

I think your cite completely miss-characterizes the FACE experiment, as shown in the 2009 revision that I posted as the OP.

[Calypso 464]

Reminds me of my grade school teachers when I was a kid.

All teachers would say the same thing if somebody would fart inside the classroom:

"Don't do that here or we would all suffocate. Your farts produce carbon dioxide that plants need. Fart towards the plants and they'll grow. Humans need oxygen."

[one...two...tree 2,762]

I think your cite completely miss-characterizes the FACE experiment, as shown in the 2009 revision that I posted as the OP.

Here's another study from the UK:

Previous studies of the effects of growth at elevated CO2 on energy partitioning in the photosynthetic apparatus have produced conflicting results. The hypothesis was developed and tested that elevated CO2 increases photochemical energy use when there is a high demand for assimilates and decreases usage when demand is low. Modulated chlorophyll a fluorescence and leaf gas exchange were measured on needles at the top of a mature, 12-m loblolly pine (Pinus taeda L.) forest. Trees were exposed to ambient CO2 or ambient plus 20 Pa CO2 using free-air CO2 enrichment. During April and August, periods of shoot growth, light-saturated photosynthesis and linear electron transport were increased by elevated CO2. In November, when growth had ceased but temperatures were still moderate, CO2 treatment had no significant effect on linear electron transport. In February, when low temperatures were likely to inhibit translocation, CO2 treatment caused a significant decrease in linear electron transport. This coincided with a slower recovery of the maximum photosystem II efficiency on transfer of needles to the shade, indicating that growth in elevated CO2 induced a more persistent photoinhibition. Both the summer increase and the winter decrease in linear electron transport in elevated CO2 resulted from a change in photochemical quenching, not in the efficiency of energy transfer within the photosystem II antenna. There was no evidence of any effect of CO2 on photochemical energy sinks other than carbon metabolism. Our results suggest that elevated CO2 may increase the effects of winter stress on evergreen foliage.

http://www.plantphysiol.org/cgi/content/abstract/120/4/1183

[I AM NOT THAT GUY 5,715]

Here's another study from the UK:

Previous studies of the effects of growth at elevated CO2 on energy partitioning in the photosynthetic apparatus have produced conflicting results. The hypothesis was developed and tested that elevated CO2 increases photochemical energy use when there is a high demand for assimilates and decreases usage when demand is low. Modulated chlorophyll a fluorescence and leaf gas exchange were measured on needles at the top of a mature, 12-m loblolly pine (Pinus taeda L.) forest. Trees were exposed to ambient CO2 or ambient plus 20 Pa CO2 using free-air CO2 enrichment. During April and August, periods of shoot growth, light-saturated photosynthesis and linear electron transport were increased by elevated CO2. In November, when growth had ceased but temperatures were still moderate, CO2 treatment had no significant effect on linear electron transport. In February, when low temperatures were likely to inhibit translocation, CO2 treatment caused a significant decrease in linear electron transport. This coincided with a slower recovery of the maximum photosystem II efficiency on transfer of needles to the shade, indicating that growth in elevated CO2 induced a more persistent photoinhibition. Both the summer increase and the winter decrease in linear electron transport in elevated CO2 resulted from a change in photochemical quenching, not in the efficiency of energy transfer within the photosystem II antenna. There was no evidence of any effect of CO2 on photochemical energy sinks other than carbon metabolism. Our results suggest that elevated CO2 may increase the effects of winter stress on evergreen foliage.

http://www.plantphysiol.org/cgi/content/abstract/120/4/1183

Can you explain what you just highlighted in plain English?

[Niels Bohr 72]

Where's HAL?

[I AM NOT THAT GUY 5,715]

Where's HAL?

Really!

[Niels Bohr 72]

Nitrogen are larger in concentration in soil. The plants could collect them from there. HAL is a medical student or former medical student. He knows better than I do.

Edited March 9, 2010 by Niels Bohr

[one...two...tree 2,762]

Can you explain what you just highlighted in plain English?

I thought you liked talking the talk with your articles and charts?