Scientists say many plants don't respond to warming as thought

March 21, 2016, Columbia University
Cotton grass flowers on the tundra of northern Alaska. A new study conducted here and elsewhere shows that the reaction of cold-region plants to higher temperatures does not proceed as previously thought. Credit: Kevin Griffin/Lamont-Doherty Earth Observatory

Plants, like people, breathe, and when it gets hotter, they breathe harder. One product of respiration is the greenhouse gas carbon dioxide. Thus, researchers predict that as the planet is warmed by human-produced CO2, plants may add to the emissions, and amplify the warming. Now, the most comprehensive global study of its kind yet suggests that this effect has limits, and that increases in plant respiration may not be as big as previously estimated. It shows that rates of increase slow in an easily predictable way as temperatures mount, in every region of earth, from tropics to tundra. The newly defined curve leads to sharply reduced estimates of respiration, especially in the coldest regions.

On the most basic level, the study suggests that all plant life has the same internal temperature controls. It looks at respiration on daily to seasonal levels and does not directly address long-term climate change, but it does suggest that plant respiration may not feed back into global warming quite as much as feared. The study appears today in the Proceedings of the National Academy of Sciences.

"What we thought was a steep curve in some places is actually a little gentler," said coauthor Kevin Griffin, a plant physiologist at Columbia University's Lamont-Doherty Earth Observatory. "With this new model, we predict that some ecosystems are releasing a lot less CO2 through leaf respiration than we previously thought." The biggest changes in estimates are in the coldest regions, which recently have seen warming far beyond that in temperate zones. "All of this adds up to a significant amount of carbon, so we think it's worth paying attention to," said Griffin.

The cells of living creatures must respire in order to build tissues and carry out basic metabolic processes. Plants take in vast amounts of carbon from the air during photosynthesis, but they also breathe much of it out in respiration. Worldwide, plants are believed to respire about 60 billion tons of CO2 each year—about six times what humans produce through burning of fossil fuels. Scientists have long known that plants respire faster when it gets hotter, and there are some fears that if global temperatures get high enough, they will become less efficient, and respiration will outweigh photosynthesis, heightening CO2 in the air.

In the lab, a custom-built gas-exchange device measures rates of leaf respiration as temperatures are increased. Credit: Kevin Griffin/Lamont-Doherty Earth Observatory

Up to now, climate models have assumed that as temperature doubles, so does , whether on daily, seasonal or longer timeframes. The authors confirmed that short-term speedups with higher temperature take place everywhere—but that the rate of increase slows along a simple, predictable curve as temperatures mount. Setting up instruments in the field and subjecting leaves to rising temperatures over half-hour spans, they measured plant responses in 231 species, from herbs and grasses to shrubs and trees. Study areas included Alaskan tundra; boreal forests in Minnesota and Sweden; temperate forest in New York's Hudson Valley; tropical areas in Peru, Costa Rica and French Guiana; and savannahs in Texas and Australia. These far-flung regions have widely differing growing-season temperatures, ranging from a mean of 8 degrees C (42 F) in Alaska to 28 C (82 F) in parts of Australia.

The scientists found that in colder regions, plants wake up quickly as things warm, and respire more at lower temperatures than their counterparts in hotter ones. However, this response dampens relatively quickly, compared to the plants in hotter areas. In other words, plants living in cold places are already working hard to begin with, and won't work too much harder after a certain point. The researchers assembled new estimates of temperature-respiration relationships that differ from current models. On the North Slope of Alaska the estimates of increase with temperature are 28 percent lower than in the now common model. In Black Rock Forest, north of New York City, they are about 15 percent lower. Griffin led the field research at both of those sites.

"The findings of this study have important consequences for estimating carbon storage in vegetation, and for predicting concentrations of atmospheric carbon dioxide and future surface temperatures," said lead author Mary Heskel, of Massachusetts' Marine Biological Laboratory. The study follows a related paper last week in the journal Nature, in which researchers did try to more directly address the question of long-term warming; they found that trees in Minnesota subjected to rising heat over several years become acclimated, and cut down their rate of respiration increase.

The new study's simple global curve points to universal internal controls that span all the world's plant life, said study leader Owen Atkin, a plant biologist at Australian National University and an adjunct at Lamont-Doherty. "Amazingly, these patterns were remarkably uniform across all the habitats and plant types," he said.

Zsofia Stangl, a student at Umea University and study coauthor, collects leaf samples from high up in a pine stand in northern Sweden. Credit: Mary Heskel

Griffin cautioned that the findings do not necessarily mean that revised climate models based on the new data will project less warming in the future. The planetary carbon cycle is vast and complex, with gases constantly moving in and out not only through plants, but soils, permafrost, lakes, oceans, volcanoes and human activities. Environmental changes that decrease CO2 release from one system may ramp it up in another. For instance, another study out last week in the journal Climate Change Responses suggests that warmer, wetter conditions in the arctic are hastening decomposition of tundra soils and permafrost, and thus releasing carbon stored there.

"We now have a better way to estimate one process, but it's only one process," said Griffin. "The whole system is quite complicated, and a small change in the balance between one part and another could produce a really big result. That's the challenge we face when we think about the earth as a whole."

The study's other authors are Odhran O'Sullivan, Lasantha Weerasinghe, Aurore Penillard, John Egerton, Danielle Creek, Keith Bloomfield, Jen Xiang and Patrick Meir of Australian National University; Peter Reich and Mark Tjoelker of Western Sydney University; Felipe Sinca of Stanford University; Zsofia Stangl of Sweden's Umea University; Alberto Martinez de la Torre and Chris Huntingford of the United Kingdom's Centre for Ecology and Hydrology; Vaughan Hurry of the Swedish University of Plant Sciences; and Matthew Turnbull of New Zealand's University of Canterbury, who is also a Lamont-Doherty adjunct.

Explore further: Climate warming accelerating carbon loss from thawing Arctic soils, study finds

More information: Convergence in the temperature response of leaf respiration across biomes and plant functional types, www.pnas.org/cgi/doi/10.1073/pnas.1520282113

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22 comments

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ogg_ogg
1.5 / 5 (8) Mar 21, 2016
There's nothing "complicated" here: they report previous estimates of CO2 release increasing with increasing T are wrong. This article implies that this may have "unknown" effects on other parts of the system. Uh, no. Smaller effect is smaller effect. Smaller effect REDUCES possible feed-back mechanisms (and ecological catastrophies). Period. Good news for the GHGW deniers, bad news for the white-eyed, ban all energy production now folks.
antigoracle
1.5 / 5 (8) Mar 21, 2016
Bang..bang...bang...one more nail in the AGW Cult's CO2 filled coffin of lies.
It's amazing how plants can defy the wishful doom and gloom of the cult. It is as if they have experienced it all before and evolved not only to survive but strive in it.

Good news for the GHGW deniers

Therein is the mindset of the indoctrinated Chicken Little ignoramus. No doom and gloom = bad news.
abecedarian
3.7 / 5 (3) Mar 21, 2016
Kind of makes sense that plants adapted for colder environments "plateau" sooner than those not so acclimated, no?

I'm not going to jump off into the whole anti-AGW thing, but this is something the models didn't predict, right?
Tangent2
2.6 / 5 (5) Mar 21, 2016
"By using the energy of sunlight, plants can convert carbon dioxide and water into carbohydrates and oxygen in a process called photosynthesis."

This is what was taught in school. Why does this article suggest that plants are breathing out CO2 when in fact the very photosynthesis process would release oxygen as the byproduct?
abecedarian
5 / 5 (8) Mar 21, 2016
"By using the energy of sunlight, plants can convert carbon dioxide and water into carbohydrates and oxygen in a process called photosynthesis."

This is what was taught in school. Why does this article suggest that plants are breathing out CO2 when in fact the very photosynthesis process would release oxygen as the byproduct?

Because during the day, they create sugars via photosynthesis, and metabolize some of those at the same time, but at night they keep metabolizing sugars they synthesized during the day but don't have photosynthesis to help them make more.
dan42day
5 / 5 (2) Mar 21, 2016
Because during the day, they create sugars via photosynthesis, and metabolize some of those at the same time, but at night they keep metabolizing sugars they synthesized during the day but don't have photosynthesis to help them make more.


Yes, that makes sense, the plant's metabolism is constrained by their food (fuel) supply, provided by photosynthesis, not temperature. However, with a sustained temperature increase without a corresponding increase in sunlight, they will have to adapt to the changing environment and eventually they will evolve. Their future oxygen/co2 balance is anybody's guess.
obama_socks
1 / 5 (5) Mar 21, 2016
Quite right. Plants have a built-in survival method for adapting to environmental circumstances, and making slight changes chemically when needed. I read somewhere that plants show fear, i.e., when about to be eaten. What could be the significance of that, I wonder.
obama_socks
1.8 / 5 (5) Mar 21, 2016
FTCause
1 / 5 (6) Mar 22, 2016
"Worldwide, plants are believed to respire about 60 billion tons of CO2 each year—about six times what humans produce through burning of fossil fuels"

6 Times the amount????? And that's just one natural process that makes human contribution look tiny. I wonder how much CO2 is added by decomposition, volcanic activity and wild fires??? I'm guessing there are trillions upon trillions of microbes contributing to the CO2 output. Oh, and we better stop breathing too. Maybe the answer is to come up with a carbon tax for each exhale from rich countries and give free exhales to the poor nations.

I do not deny climate change. It's been changing forever and of course warming since the last ice age. What I deny is the human ability to 1) identify precisely our contribution 2) predict actual future negative results 3) control the earths cycle of events.

Seems to me there are plenty of city ruins in the Mediterranean complete under water because of climate change and they adapted.
leetennant
4 / 5 (8) Mar 22, 2016
The main thing this article seems to have proven conclusively is that deniers can't read. The psychological impacts of denial have become as fascinating to me as climate science.

Firstly, all this article is talking about is us improving our understanding of plant respiration. Yes, plants emit CO2. It's a shocker, I know. But then if you're denying basic physics I guess it's no surprise basic biology is a mystery to you too.

All this is saying is that increasing temperatures will affect plant respiration in colder areas more than in hotter areas and so our original "1 degree = double respiration" estimate is oversimplified. Plants already respiring more because of heat won't have the same proportional increase in respiration as others that aren't.

Plant respiration is one area where we know we needed more information. This research will change climate models but is unlikely to impact the headline indicators.
chapprg1
5 / 5 (2) Mar 26, 2016
Plants convert some of the CO2 to sugar and O2. Net reduce carbon, exhale O2. Their night time metabolism and their decay when they die will give back some of the CO2 which they have previously sequestered . The net is O2 . Where do you think the 20% O2 of our atmosphere came from?
Ojorf
5 / 5 (1) Mar 27, 2016
Plants convert some of the CO2 to sugar and O2. Net reduce carbon, exhale O2. Their night time metabolism and their decay when they die will give back some of the CO2 which they have previously sequestered . The net is O2 . Where do you think the 20% O2 of our atmosphere came from?


Not quite, if the plant dies and decomposes or is consumed or burns, none of those result in a net O2.
Only if the plants biomass is permanently stored somehow will that be true, like fossil fuels used to do, you know.
antigoracle
1 / 5 (4) Mar 27, 2016
All this is saying is that increasing temperatures will affect plant respiration in colder areas more than in hotter areas and so our original "1 degree = double respiration" estimate is oversimplified.

All you are saying is that you are a retarded moron, who can't read, far less comprehend. This study conclusively shows the climate models got it WRONG. So instead of stating that, you spew shite like "1 degree = double respiration".
leetennant
5 / 5 (4) Mar 27, 2016
Plants convert some of the CO2 to sugar and O2. Net reduce carbon, exhale O2. Their night time metabolism and their decay when they die will give back some of the CO2 which they have previously sequestered . The net is O2 . Where do you think the 20% O2 of our atmosphere came from?


While this is probably aimed at FTCause who doesn't seem to understand that plants are a carbon sink overall, the problem lies in assuming that plants will always be a carbon sink in a high CO2 world. Or rather, that the difference between their CO2 and O2 emissions is stable (which we know it isn't).

Plants experiencing higher temperatures respire more and this changes the extent to which they are a carbon sink. If 1 degree = double respiration across the board, this had the potential to be a HUGE issue. So yes it's some good news that the respiration change isn't uniform. But it's hardly a smoking gun for climate models.
antigoracle
1 / 5 (4) Mar 28, 2016
Leetentard, please get someone with a brain to read and explain the article to you.

climate models have assumed that as temperature doubles, so does plant respiration

The above does not mean 1 degree = double respiration across the board, as you keep repeating you idiot.
Phys1
5 / 5 (4) Mar 28, 2016
"Up to now, climate models have assumed that as temperature doubles, so does plant respiration, whether on daily, seasonal or longer timeframes."
If "temperature doubles" it will rise by at least 273 K so all plants will go up in smoke.
Phys1
5 / 5 (4) Mar 28, 2016
the indoctrinated Chicken Little ignoramus.

Chucky is at it again.
Phys1
5 / 5 (4) Mar 28, 2016
Leetentard, please get someone with a brain to read ... you idiot.

Chucky is smart !
antigoracle
1 / 5 (4) Mar 28, 2016
the indoctrinated Chicken Little ignoramus.

Chucky is at it again.

Your wife said you were at it again... back in her underwear drawer trying her things.
gkam
3 / 5 (4) Mar 28, 2016
anti, please stop the abusive nastiness.
Phys1
5 / 5 (3) Mar 28, 2016
@chucky
Chucky is evil and perverse.
I prefer chicken little.
leetennant
5 / 5 (1) Mar 31, 2016
"Up to now, climate models have assumed that as temperature doubles, so does plant respiration, whether on daily, seasonal or longer timeframes."
If "temperature doubles" it will rise by at least 273 K so all plants will go up in smoke.


In fact, the paper this article refers to just says that increases in plant respiration due to temperature increases were thought to be exponential. So neither anti or I were strictly correct. Plus, I think this means that anti actually read an article for once. I think we should mark the date and time.

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