2011-03-30 09:10:07Edit 3rd draft, CO2 is plant food
Dawei

dlbrooks87@gmail...
24.250.223.217

EDIT: Scroll down for 3rd draft. In the same post that the 2nd draft was in.

______________________________________________________________________

 

As for sources, I used a few links that I found myself as well as many from the SS page for this argument.

Note that I tried to focus it mainly on the direct effects of CO2 on plant life, and not on the effects of climate change on plant life. This is because I think that the effect of climate change on plants is a separate and much larger topic, and frankly a somewhat obvious argument to make.  I did however emphasize its importance by using it as my leading argument. If people strongly feel that I should focus the article on the effects of climate change on plants, then I will be willing to change, but I hope you understand my reasoning for wanting to focus it on the direct effects of CO2 itself.  

 

 

CO2 is “plant food”

The skeptic argument: CO2 is plant food, therefore increasing atmospheric concentrations will universally increase plant yield

What the science says: The effects of enhanced CO2 on plants are far more variable and complex than most people realize

 

In climate change debates, even AGW proponents frequently accept the CO2 fertilization effect as a ‘given’; a common remark is that industrial greenhouse owners will pump CO2 levels far higher than normal in order to increase yields. Thus, the idea that “more CO2 = more growth” is simply accepted as a given, across all plant species and all situations. This is, however, a drastic oversimplification of an area of study that is still evolving.

Climate control vs. climate change

The first and most obvious retort to this argument is that plants require more than just CO2 to live. Owners of industrial greenhouses who use excess CO2 invest considerable effort in keeping their plants at optimum growing conditions, particularly with respect to temperature and moisture. In a changing climate, both of these variables may change in an unfavorable way for a certain species in a certain region, counteracting any potential benefit from excess CO2 (Lobell et. al 2008, Luo 2009, Zhao and Running 2010, Challinor et. al 2010, Lobell et. al 2011).

But there is also an important, more subtle point to be made here. The majority of scientific studies on enhanced CO2 to date have been performed in greenhouse-type settings. Only recently have researchers begun to pull away from the controlled greenhouses and turn their attention to outdoor environments. Known as Free-Air CO2 Enrichment or “FACE”, these studies are clearly superior to a greenhouse in their ability to describe plant behavior in a world with enhanced atmospheric CO2. Unfortunately, the results of these studies are not nearly as promising, with final yield values averaging around 50% less in the free-air studies compared to greenhouse studies (Long et al. 2006; see also Ainsworth 2005 and Morgan et al. 2005). Reasons for this are numerous, but it is suspected that in a greenhouse, the isolation of individual plants, constrained root growth, restricted pest access, lack of buffer zone, and unrealistic atmospheric interactions all contribute to artificially boost growth and yield under enhanced CO2

C3 ≠ C4

Photosynthesis comes a few different flavors, with the most important being “C3” and “C4”. These two types make up the bulk of modern agriculture, with wheat and rice being examples of C3 crops while corn and sugarcane are C4. It has long been known that excess CO2 is much more beneficial to the C3 variety of photosynthesis compared to C4, due to the distinct enzymes used in each variety. Cure and Acock 1986 (a greenhouse study) showed excess CO2 gave a 35% photosynthesis boost in rice and 32% boost for soybeans (both C3 plants), but only a 4% boost for C4 crops. More recently, Leaky et al. 2006 (a FACE study) did not find any statistically significant boost in photosynthesis or yield for corn under excess CO2.

The ‘immunity’ of C4 plants to the benefits of excess CO2 may be particularly worrisome since corn is expected to become the world’s most important staple food by 2020 (Pingali and Pandey 2000), and because both corn and sugar are frequently championed as the eventual replacement for crude oil. 

Even within a specific type of photosynthesis—indeed, even within a specific species—the positive responses to enhanced CO2 can vary widely. Nutrient availability can greatly affect a plant’s response to excess CO2 as well, with phosphorous and nitrogen being the most critical (Stöcklin & Körner 2002, Norby et. al 2010, Larson et. al 2010). Positive effects may also be reduced due to responses of symbiotic root fungal colonies (aka ‘mycorrhizae') to enhanced CO2 (Newman 1988). Other factors such as age, genetic variations, time of year, temperature, bacterial colonies, sunlight intensity, soil moisture, or presence of nearby individuals can all affect the plant’s response to excess CO2 (Körner 2000).

▪ Temperature

As if the picture were not already complex enough, further more intricate reactions to excess CO2 have been noted. It has long been known, for example, that stomata (the pores through which plants take in CO2 and exhale oxygen and water) tend to be more narrow and stay closed longer under enhanced CO2, presumably a benefit as it reduces water loss. However this is, too, an oversimplification. About 90% of a plant’s water requirements are actually for cooling, and nothing more. Liquid water enters the roots, absorbs excess heat, and escapes the stomata as water vapor. Thus while it is true that the plant may require less water under enhanced CO2, it is also retaining more heat. This can carry plants outside of the optimum range of photosynthesis (Ball et al. 1988 and Idso et al. 1993.) An image present in Long et al. 2006 (above) shows this effect quite clearly; and while a 1.4 C increase is probably not enough to cause significant damage in most cases, global warming will only serve to exacerbate the effect. 

CO2 raises temperatures

(From Long 2006).

▪ Chemical responses

Increased CO2 has been shown to lead to lower production of certain chemical defense mechanisms in soybeans, putting them more vulnerable to pest attack (another effect which is not aptly accounted for in controlled greenhouse studies due to walls and isolation (Long et al. 2006). Other studies (e.g., Peñuelas & Estiarte 1999) have shown production of phenolics and tannins to increase under enhanced CO2 in some species, having far ranging consequences on the health of primary consumers.

▪ Other gasses

CO2 is not the only atmospheric gas that is on the rise: concentrations of tropospheric ozone (O3) are expected to increase by 23% by 2050. O3 has long been known to be toxic to plants: Morgan et al. 2006 found a 20% reduction of soybean yield in a FACE...

2011-03-30 09:11:49
Dawei

dlbrooks87@gmail...
24.250.223.217

...study of 23% excess O3. Furthermore, Monson et al 1991 found that emissions of VOCs (a major cause of tropospheric ozone) increase under excess CO2 in many species, thereby introducing the potential that local O3 concentrations around plant communities may rise even higher than the baseline atmospheric level.

Conclusions

Current direct experimental evidence indicates that the effect of excess CO2 on plant growth is confounded by variables which are numerous and often difficult to quantify. In addition to experimental evidence, proxies indicating plant growth responses to past CO2 changes have also shown limited benefits of increased CO2 on growth (Gedalof and Berg, 2010). The global effects on plants of the enhancement of atmospheric CO2 is a grand experiment whose results may not be anticipated with any degree of certainty.

2011-03-31 15:10:46comments
dana1981
Dana Nuccitelli
dana1981@yahoo...
69.230.97.203

Hey Dawei, welcome aboard!  Nice job, a few comments:

"In climate change debates, even AGW proponents frequently accept" <= we don't usually use the term "AGW proponents" here, though I always have trouble finding a suitable term.  Maybe revise to "Everybody seems to accept..." or "It's almost universally accepted..."

It would be good to give a little description about how FACE experiments are set up when you first introduce the concept.  How do they simulate elevated CO2 in open air?

"Photosynthesis comes a few different flavors, with the most important being “C3” and “C4”." <= I'd give a brief description about exactly what C3 and C4 mean here.

"More recently, Leaky et al. 2006 (a FACE study) did not find any statistically significant boost in photosynthesis or yield for corn (a C4 crop) under excess CO2."

"...both corn and sugar are frequently championed as the a possible eventual replacement for crude oil. "

"Positive effects may also be reduced due to responses of symbiotic root fungal colonies (a.k.a. ‘mycorrhizae')"

"As if the picture were not already complex enough, further even more intricate reactions to excess CO2 have been noted."

"...more narrow and stay closed longer under enhanced CO2, which is presumably a benefit, as it reduces water loss"

"An image presented in Long et al. 2006 (aboveFigure 1) shows this effect" <= then label the image "Figure 1"

"(another effect which is not aptly accounted for in controlled greenhouse studies due to walls and isolation, according to (Long et al. 2006)."

"concentrations of tropospheric ozone (O3) are expected to increase by 23% by 2050." <= why?

Nice conclusion.  Maybe add that the assumption that more CO2 will necessarily increase plant yield is an incorrect oversimplification. 

Overall really good job.  Very interesting and well-researched.

2011-04-02 07:54:04
Dawei

dlbrooks87@gmail...
24.250.223.217

Thanks for the comments Dana. I've made all of your suggested changes.


I think I will email it to david b now to see if he has anything to critique/add. When I draw up a second draft, do I enter it as a new post under this thread? Or should I just edit my original post?

2011-04-02 08:48:21New post or edit
John Cook

john@skepticalscience...
124.185.238.238
Either is fine - either way, make sure you edit the top post to clearly and loudly announce that it is either an edit new draft (change the title) or point to an updated version lower down. That way, we're properly orientated when we visit this thread.
2011-04-02 14:20:36
Dawei

dlbrooks87@gmail...
24.250.223.217

Thanks John. I know you had started on an article about this too, do you have any ideas on what I could add to it or change?

2011-04-06 05:30:08
Dawei

dlbrooks87@gmail...
24.250.223.217

CO2 is “plant food”

The skeptic argument: CO2 is vital for photosynthesis, therefore increasing atmospheric concentrations will universally increase plant growth

What the science says: The effects of enhanced CO2 on terrestrial plants are variable and complex and dependent on numerous factors

In the climate change debate, it appears to be agreed by everyone that excess CO2 will at least have the direct benefit of increasing photosynthesis, and subsequently growth rate and yield, in virtually any plant species: A common remark is that industrial greenhouse owners will raise CO2 levels far higher than normal in order to increase the yield of their crops, so therefore increasing atmospheric levels should show similar benefits. Unfortunately, a review of the literature shows that this belief is a drastic oversimplification of a topic of study that has rapidly evolved in recent years.

Climate control vs. climate change

The first and most obvious retort to this argument is that plants require more than just CO2 to live. Owners of industrial greenhouses who purchase excess CO2 also invest considerable effort in keeping their plants at optimum growing conditions, particularly with respect to temperature and moisture. As CO2 continues to change the global climate, both of these variables are subject to change in an unfavorable way for a certain species in a certain region (Lobell et al. 2008, Luo 2009, Zhao and Running 2010, Challinor et al. 2010, Lobell et al. 2011). More and more it is becoming clear that in many cases, the negatives of drought and heat stress may cancel out any benefits of increased CO2 predicted by even the most optimistic study. 

But there is a more subtle point to be made here. The majority of scientific studies on enhanced CO2 to date have been performed in just these types of enclosed greenhouses, or even worse, individual growth chambers. Only recently have researchers begun to pull away from these controlled settings and turn their attention to outdoor experiments. Known as Free-Air CO2 Enrichment or “FACE”, these studies observe natural or agricultural plants in a typical outdoor setting while exposing them to a controlled release of CO2, which is continuously monitored in order to maintain whichever ambient concentration is of interest for the study (see Figure 1).

Figure 1 - Example FACE study in Wisconsin, USA with multiple CO2 injection plots; courtesy of David F Karnosky, obtained from Los Alamos National Laboratory.

FACE studies are therefore superior to greenhouse studies in their ability to predict how natural plants should respond to enhanced CO2 in the real world; unfortunately, the results of these studies are not nearly as promising as those of greenhouse studies, with final yield values averaging around 50% less in the free-air studies compared to greenhouse studies (Leaky et al. 2009, Long et al. 2006, Ainsworth 2005, Morgan et al. 2005). Reasons for this are numerous, but it is suspected that in a greenhouse, the isolation of individual plants, constrained root growth, restricted pest access, lack of buffer zones, and unrealistic atmospheric interactions all contribute to artificially boost growth and yield under enhanced CO2.

C3 & C4

Photosynthesis comes in a few different flavors, two of which are C3 and C4. Together C3 and C4 photosynthesis make up almost all of modern agriculture, with wheat and rice being examples of C3 crops while corn and sugarcane are C4. The distinction deals mainly with the specific enzyme that is used to collect CO2 for the process of photosynthesis, with C3 directly relying on the enzyme RuBisCO. C4 plants also use RuBisCO, but unlike C3 plants, they first collect CO2 with the enzyme PEP-carboxylase in the mesophyll cell prior to pumping it to RuBisCO (see Figure 2).

Figure 2 - A simplified diagram contrasting C3 vs. C4 plant photosynthesis. From Nature Magazine.

The relevance of this distinction to excess CO2 is that PEP-carboxylase has no natural affinity for oxygen, whereas RuBisCO does. RuBisCO will just as readily collect oxygen (which is useless) as it will CO2, and so increasing the ratio of CO2/O2 in the atmosphere increases the efficiency of C3 plants; the extra step in the C4 process eliminates this effect, since the mesophyll cell already serves to concentrate pure CO2 near RuBisCO. Therefore excess CO2 shows some benefit to C3 plants, but no significant benefit to C4 plants. Cure and Acock 1986 (a greenhouse study) showed excess CO2 gave a 35% photosynthesis boost to rice and a 32% boost to soybeans (both C3 plants), but only a 4% boost to C4 crops. More recently, Leaky et al. 2006 (a FACE study) did not find any statistically significant boost in photosynthesis or yield for corn (a C4 crop) under excess CO2.

Going a bit deeper, it has recently been found that in some C3 plants—such as cotton and many bean species—a further enzyme known as RuBisCO activase is required to convert RuBisCO into its “active” state, the only state in which it can be used for photosynthesis. The downside of this is that the activase enzyme is much more sensitive to high temperatures compared to RuBisCO itself, and also responds poorly to excess CO2: Heat can destroy the structure of the activase enzyme at temperatures as low as 89.6 F, while excess CO2 reduces the abundance of the cellular energy molecule ATP that is critical for RuBisCO activase to function properly (Crafts-Brandner & Salvucci, 2000, Salvucci et al. 2001). This effect may potentially nullify some of the gains expected from excess CO2 in these plants. 

Chemical Responses & Nutrition

Even within a specific type of photosynthesis—indeed, even within a specific species—the positive responses to enhanced CO2 can vary widely. Nutrient availability in particular can greatly affect a plant’s response to excess CO2, with phosphorous and nitrogen being the most critical (Stöcklin and Körner 2002, Norby et al. 2010, Larson et al. 2010). The ability of plants to maintain sufficient nitrogen under excess CO2 conditions is also reduced for reasons not fully understood (Bloom et al. 2010, Taub and Wang 2008).

It has also been found that excess CO2 can make certain agricultural plants less nutritious for human and animal consumption. Zhu 2005, a three-year FACE study, concluded that a 10% decrease in the protein content of rice is expected at 550 ppm, with decreases in iron and zinc contents also found. Similarly, Högy et al. 2009, also a FACE study at 550 ppm, found a 7% drop in protein content for wheat, along with decreased amino acid and iron content. Somewhat ironically, this reduction in nutrient content is partially caused by the very increase in growth rates that CO2 encourages in C3 plants, since rapid growth leaves less time for nutrient accumulation.

Increased CO2 has been shown to lead to lower production of certain chemical defense mechanisms in soybeans, making them more vulnerable to pest attack and diseases (Zavala et al. 2008 and Eastburn et al. 2010). Other studies (e.g. Peñuelas and Estiarte 1999) have shown production of phenolics and tannins to increase under enhanced CO2 in some species, as well as many alkaloids (Ziska et al. 2005), all of which may have potential consequences on the health of primary consumers. The decreased nutritional value in combination with increased tannin and phenolic production has been linked to decreased growth rate and conversion efficiency of some herbivores, as well as an increase in their relative demand and consumption of plants (Stiling and Cornelissen 2007).

Furthermore, many “cyanogenic” species—plants which naturally produce cyanide, and which include 60% of all known plant species—have been found to increase their cyanide production in an enhanced CO2 world. This may have a benefit to the plants who use cyanide to inhibit overconsumption by pests and animals, but it may in turn reduce their safety as a food supply for both humans and animals (Gleadow et al., 2009a and Gleadow et al. 2009b).

Interactions with other species

Competing plant species have also been shown to drastically alter expected benefits from excess CO2: even in the best FACE studies, most research still involves artificial experimental plots consisting of fewer than five plant species, and often only one species is present. It has long been understood that due to increased growth of competitor species, benefits from isolated experiments cannot be scaled up to explain how a plant might respond in a monoculture plot (Navas et al. 1999). The distinction is even greater when comparing the behavior of isolated species to those of mixed plots (Poorter and Navas 2003). The lack of correlation (r2 = 0.00) between biomass enhancement (BER) of isolated plants and that of plants in mixed plots is presented in Figure 3.

Figure 3 – Isolated vs. mixed biomass enhancement ratios under excess CO2; From Figure 8 of Poorter and Navas 2003

That some plant species may benefit more fully and/or rapidly from excess CO2 also introduces the possibility that the abundance of certain species in an ecosystem will increase more than that of others, potentially forcing the transformation from one type of ecosystem to another (Poorter and Navas 2003). There is also some evidence suggesting that invasive species and many “weeds” may show relatively higher responses to elevated CO2 (Ziska and George 2004), and become more resistant to conventional herbicides (Ziska et al. 2004, Ziska and Teasdale 2000).

There is some evidence that interacting bacterial communities, particularly in the roots, will be affected through elevated CO2, leading to mixed results on overall plant health. Mutualistic fungal  root communities (known as ‘mycorrhizae') are typically shown to increase under excess CO2, which facilitate nutrient transport to the roots (Treseder 2004), although infections of pathogenic species such as Fusarium (the agent of the disease known as ‘crown rot’) have been shown to become more severe under excess CO2 as well (Melloy et al. 2010).

Temperature

It has long been known that stomata (the pores through which plants take in CO2 and exhale oxygen and water) tend to be narrower and stay closed longer under enhanced CO2. This effect is often cited as a benefit in that it increases water efficiency in drought situations.

But there is another key piece to reduced stomatal conductance, considering that 90% of a plant’s water use is actually for cooling of the leaves and nothing more: heat from the sun is absorbed by the water in the leaf, then carried out as vapor in the form of latent heat. So while it is true that the plant may retain water better under enhanced CO2, doing so may cause it to retain more heat. This can potentially carry a plant to less optimal temperature ranges (Ball et al. 1988 and Idso et al. 1993.) An image present in Long et al. 2006 (Figure 4) shows this effect quite clearly; while a 1.4 C increase is probably not enough to cause significant damage in most cases, global warming will only serve to exacerbate the effect.  It is also of note that the study above represented a well-watered situation, and so during a drought condition the temperature increase would be even higher. 

Figure 4 - Increase in local temperature under enhanced CO2 due to reduced evapotranspiration. From Long et al. 2006

On the cold end, it has been found that for seedlings of some species of evergreen trees, excess CO2 can increase the ice formation temperature on the leaves, thereby increasing their sensitivity to frost damage (Roden et al. 1998).

Ozone

CO2 is not the only atmospheric gas that is on the rise: concentrations of ground-level ozone (O3) are expected to rise 23% by 2050 due to continuing anthropogenic emissions of precursor gases like methane and nitrous oxides. In addition, Monson et al. 1991 found that natural plant emissions of volatile organic compounds (another group of O3 precursors) increase under excess CO2 in many plant species, thereby introducing the potential that local O3 concentrations around plant communities may rise even higher than the baseline atmospheric level.

O3 has long been known to be toxic to plants: Morgan et al. 2006 found a 20% reduction of soybean yield in a FACE study of 23% excess O3. Similarly, Ainsworth 2008 showed a 14% decrease in rice yield at 62 ppb O3, and Feng et al. 2008 (a meta-analysis of 53 peer-reviewed studies) found on average a 18% decrease in wheat yield at 43 ppb O3. Ozone also appears to reduce the structural integrity of plants as well as make them more vulnerable to certain insect pest varieties such as aphids (Warrington 1988).

Figure 5 - Yield reduction for several crop species under excess ozone. From Wang and Mauzeral 2004

With respect to this effect, excess CO2 may actually prove beneficial in that it causes a narrowing of leaf stomata, thereby reducing the quantity of ozone that can enter the more sensitive internal tissues. Needless to say, the combined effect of excess CO2 and excess O3 is complex, and as it has only recently been given attention it is an area that requires much further research.

Conclusion

A specific plant’s response to excess CO2 is sensitive to a variety of factors, including but not limited to: age, genetic variations, functional types, time of year, atmospheric composition, competing plants, disease and pest opportunities, moisture content, nutrient availability, temperature, and sunlight availability. The continued increase of CO2 will represent a powerful forcing agent for a wide variety of changes critical to the success of many plants, affecting natural ecosystems and with large implications for global food production. The global increase of CO2 is thus a grand biological experiment, with countless complications that make the net effect of this increase very difficult to predict with any appreciable level of detail.

2011-04-06 09:11:44Comments
John Cook

john@skepticalscience...
60.231.60.165

Thanks, this is a great post. Really interesting about the different response from C3/C4 plants and while I'd heard of the narrower stomata leading to less water loss, it never occurred to me that this meant less cooling. Of course, it's obvious now! :-)

I have one main comment and welcome opposing thoughts to my opinion - I could be off base. But I always look for a simple take-home point (if there is one available) that the average person can grasp and remember. In the case of "CO2 is plant food", my understanding is the take-home is "the negatives of drought and heat stress cancel out the benefits of increased CO2". Or the catchy metaphor, "saying CO2 is plant food is like offering a biscuit to a burning man".

You touch on this briefly but I wonder if it deserves more attention - there's a reason why it's the "first and obvious retort". You give a lot of attention to the more subtle aspects of the CO2 argument but the big, main reasons why increased CO2 is not good for plant growth is only touched on briefly. I would suggest fleshing out this section.

2011-04-06 13:35:49nice
dana1981
Dana Nuccitelli
dana1981@yahoo...
69.230.97.203

Looks good Dawei.  I'd move Figure 1 into the Temperature section though, after you reference it.

Other gasses <= no double 's'

2011-04-10 03:36:16
Dawei

dlbrooks87@gmail...
24.250.223.217

Thanks John. I added your suggested addition--you are probably right that the article should emphasize the effects of climate change. As I said I was just nervous about repeating the same old thing, because it seems like any time someone responds to the 'CO2 is plant food' argument, their retort is always 100% about climate change, so I figured most readers would know all about this anyway.

Not to mention that most deniers will probably not be swayed by arguments based on climate change since they don't believe that exists in the first place. Most of them at least agree that CO2 is rising though, so some of these direct effects might have a better chance at raising an eyebrow. But I do agree that global warming will probably be the most important effect.

I'm sure there is a lot more too that I haven't considered yet. I see that the article stays here until it gets 5 thumbs up, which seems to take a while, so in the mean time I'll keep searching for some new points that can be added in.

2011-04-10 07:27:38thumbs
dana1981
Dana Nuccitelli
dana1981@yahoo...
69.230.97.203

Don't worry about thumbs, Dawei.  The five thumbs rule pretty much only applies to Basic rebuttals where there are a lot of authors.  Not too many people read the Advanced rebuttals.  I think you've got the okay from me and John, which is sufficient.

When you feel ready, claim the advanced 'CO2 is plant food' rebuttal (Argument #120) and then edit it with your rebuttal.  Also, if you can slim it down to Intermediate and/or Basic versions, claim and edit those as well.  Then when you're done, we'll take one of them (probably Intermediate, if you claim that one) and make a blog post about it.

2011-04-13 16:36:30Basic rebuttal
John Cook

john@skepticalscience...
60.231.60.165

Villabolo has just written a basic rebuttal which seems to follow similar lines to this advanced rebuttal:

http://www.skepticalscience.com/thread.php?t=1345&r=0

How shall we proceed? I'd say it makes sense to publish a basic version first to introduce the subject then go with the advanced version. Sound ok?

If so, Dawei, I suggest having a look at Villabolo's basic rebuttal, we publish that then shortly afterwards post your advanced version.

2011-04-14 00:45:15suggestion
dana1981
Dana Nuccitelli
dana1981@yahoo...
69.230.97.203

Maybe post Villabolo's with a note that it's an introductory/basic post which will be followed with a more in-depth examination of the issue, then post Dawei's shortly thereafter?

2011-04-14 07:28:12Agreed
John Cook

john@skepticalscience...
60.231.60.165
Green box at end of villabolo's post "this is basic rebuttal of ... An advanced rebuttal is coming soon..."
2011-04-14 13:55:46
Dawei

dlbrooks87@gmail...
24.250.223.217

Sounds fine to let him publish first.

I really liked his point about the reduced nutritional value of wheat, and the increased fire risk from denser vegetation is interesting too. Should I add that to this rebuttal? Or is it OK if the 'advanced' version doesn't include all of the same info that the 'basic' one does?

I already added his references relating to increased susceptibility to pests and diseases, since I already had mentioned that but didn't have direct references for them.

2011-04-14 15:40:56Add
dana1981
Dana Nuccitelli
dana1981@yahoo...
69.230.97.203
I think it wouldn't hurt to add the reduced nutritional value to the advanced, Dawei. Just a brief mention should suffice.
2011-04-19 01:18:01
Dawei

dlbrooks87@gmail...
24.250.223.217

So I see the basic rebuttal has been posted. I've been reading the comments to see if anyone has anything constructive to say that could be added into the advanced version before it goes live. Some great extra information has already been posted by other users that I think would fit well into the advanced version.

Is there a way I can contact some of the posters who had decent comments to see if they have any more info to offer? Among them Alec Cowan, Witsendnj, LukeW, Glenn Tamblyn, Marcus, Ian Forester. There is no way to go clicky on their names.

2011-04-19 12:29:40email
dana1981
Dana Nuccitelli
dana1981@yahoo...
69.230.97.203
I emailed those to you. So you want to hold off on your blog post for a bit?
2011-04-19 13:59:55
Dawei

dlbrooks87@gmail...
24.250.223.217

Thanks Dana.

Yeah I think it would be good to wait just a few more days. There really were quite a few great points mentioned in the comments, with some interesting sources that I want to read through. After that it will probably need to be reorganized. I'm also going to add in a few more pictures. 

I'll post a third draft here when it's all added in.

2011-04-19 14:18:27cool
dana1981
Dana Nuccitelli
dana1981@yahoo...
69.230.97.203

Sounds good Dawei.  Look forward to seeing the next draft.

2011-04-26 13:38:04
Dawei

dlbrooks87@gmail...
24.250.223.217

Alright, the most recent (final?) draft is up. A lot of the added info was contributed from the commenters of villabolo's post.

Dana, you said I needed to slim it down for the blog post. I'm not sure exactly which parts should be cut; if you have some suggestions that would be great.

If no one has any other comments, I think it's ready to go live.

2011-04-26 14:53:45cool
dana1981
Dana Nuccitelli
dana1981@yahoo...
69.230.97.203

Nice.  i like the new figures.  Looks good to me after a quick read through.  We'll leave it for a day or two to see if there are any comments, and if not, publish.

Since villabolo did the basic version, I think we can go ahead and post this one as-is without having to worry about shortening it.

2011-04-26 15:09:36Very thorough
Daniel Bailey
Daniel Bailey
yooper49855@hotmail...
97.83.150.37

My small contribution:  Labels for Fig's 1 and 2 are italic, labels for Fig's 3-5 are not.

Suggest changing labels for Fig's 3, 4, and 5 to italic.

Rest looks good!

2011-04-27 15:05:12
Dawei

dlbrooks87@gmail...
24.250.223.217

Awesome! Thanks to whoever published it. And I like the title :)

2011-04-28 13:15:25kudos
dana1981
Dana Nuccitelli
dana1981@yahoo...
69.230.97.203

Glad you liked it.  It's getting some great reviews from commenters, and well-deserved.  Great job!