Rainforest study: Scientists now know the temperature at which photosynthesis stops

[applegrove]

Rainforest study: Scientists now know the temperature at which photosynthesis stops

Heat is just one of many stressors for the world’s beleaguered Amazon
By KATIE MYERS
PUBLISHED AUGUST 29, 2023 7:27AM (EDT)

https://www.salon.com/2023/08/29/rainforest-study-scientists-now-know-the-temperature-at-which-photosynthesis-stops_partner/

"SNIP........

Around the world, leaves play a critical central role in staving off the worst impacts of climate change. Their ability trap CO2 and combine it with water and sunlight to make food and oxygen is a critical part of what keeps life on Earth going. But according to a new study published in Nature, some tropical forests — including the Amazon rainforest — could become too hot for leaves to photosynthesize.

The Amazon rainforest was once one of the world's most powerful carbon sinks, largely a result of its uniquely dense tree cover. But deforestation has slowly eaten away at its edges, and drought and fire have limited rainforests' ability to withstand extreme temperatures. The Amazon was even a net carbon emitter for the first time in 2021. Still, the Amazon covers a land area roughly twice the size of India, and is among the most biodiverse ecosystems on Earth, with over 3 million species of flora and fauna.

All that could be lost if temperatures continue to increase, potentially turning once-lush tropical forests into a savannah-like plain. According to the study, photosynthesis in tropical trees begins to fail at about 46.7º degrees C (116º degrees F). In addition to monitoring the canopy using both research towers and high resolution images from the International Space Station, the research team heated leaves up in order to test the effects of higher temperatures, identifying the critical threshold at which the enzymes necessary for photosynthesis break down. The data was collected every few days from forests all over the world.

...........

Though it doesn't happen instantaneously, lengthy hot spells increase stress on the leaves, eventually killing them. If enough leaves die, the tree dies with them. And if enough trees die, so does the forest.

.........SNIP"

[BComplex]

1. The trees in my area of the world are being cut down and sold off at an alarming rate. 400 acres at

a time. It makes my blood curdle.

[applegrove]

2. The good news is the internet has cut down the need for paper. So forests

Last edited Thu Aug 31, 2023, 01:19 AM - Edit history (2)

are safer than in my great grandfather's generation where he went out west to make his fortune in the lumber industry and died doing it. They used to use wood for everything. There used to be a match factory way back when in Ottawa.I guess people needed to light their wood stoves and wood burning fireplaces. So much has changed. Even decks are no longer being built out of wood. So there is some hope. If we can just cut back on CO2.

[orthoclad]

5. Civil war pictures had few trees in them.

The land was cleared for farming. The East, at least, has reforested to an extent. Many of these areas now have second-growth forests, which are a poor replacement for a healthy mature forest. Unfortunatley, white flight led to a new wave of deforestation for suburban development.

Development and agriculture destroyed far more forest than paper. Before coke ovens, metallurgical charcoal took a lot of trees, I think 9 acres forest for a ton of iron.

I don't think the loss of paper to the internet is so good. Server farms use vast amounts of energy, and we've barely begun to see the consequences of replacing skilled journalism with instant-gratification microblogs. Also, paper doesn't come with tracking pixels, cookies, and scripts. People are going to jail now for researching abortion online (there are no phone books anymore), and we lose 2 local newspapers per week.

I read year's-best compilations of fiction. The ones with primarily online sources show a clearly lower quality than ones from print sources. When you do the greater work of print publishing, editing and composition get more time and attention.

I download text from Project Gutenberg to read in waiting rooms (Ambrose Bierce is ideal), but for pleasure I read paper books.

Interestingly, research has shown that the great "primeval" Eastern forest was actually heavily managed before Euro contact. Indigenous people took generations to cycle land from ag to scrub to mature forest and back again. This is why English colonial shipbuilders were so astounded at the quality of Eastern timber.

[applegrove]

7. Yes. I've heard the east coast is re-foresting itself. I hope that continues.

[orthoclad]

8. I think we have net deforestation, though,

over the US. Timber harvest and development, and now disease and wildfire.
The East is losing all its oak trees to a blight, now. Red oaks first, then white oaks are succumbing. Wildlife will starve from lack of acorns.

[applegrove]

9. Oh that is sad. And bad.

[orthoclad]

10. We lose species after species

Chestnut, elm, ash, now oak.
Won't be many valuable species left soon -- valuable to wildlife, that is.
Much of this is due to rapid global trade, which spreads disease and invasive species like lightning.

I've tried planting blight-resistant American chestnut. A few are surviving.

[applegrove]

11. I remember Dutch elm disease as a kid in Ottawa. They were taking

down those once majestic trees everywhere. I don't think I've seen a real elm leaf since I was about 6.

[orthoclad]

12. In ecology they use the airplane analogy

You can take out rivet after rivet without the plane falling apart, but eventually it will. All those weak joints will go at once.

[applegrove]

13. Yes. It will happen overnight when it fails.

[LT Barclay]

3. The Dying of the Trees by Charles E. Little. One of the most depressing books I've ever read.

Covers 6 different forests being destroyed by 6 different plagues.

[orthoclad]

14. I couldn't read it.

Too depressing.

[LT Barclay]

15. You didn't miss anything you didn't already know.

It was like a 70’s disaster movie, you know how it will end, so skip it and save yourself the grief.

[orthoclad]

16. No, I'm a scientist,

I've seen, read, documented, and tried to fix lots of ecological damage. But I couldn't handle the additional grief. I'd heard a summary on the radio, tried the book, but couldn't deal with the grief.

[LT Barclay]

17. The grief thing is real and I get it.

I’ve been thinking that a lot of people could benefit from a public expression of that grief. Off and on I’ve been working with a couple of guys on an endangered species opera but the project is kind of stalled.
I performed my version as a puppet show and I hope to post it soon as soon as I can figure out filmora. We performed it in front of Jean-Michel Cousteau at a family camp on Catalina Island in CA.

[LastDemocratInSC]

4. I have been preaching the news about this for years

because the temp at which photosynthesis stops varies by the plant species and for many domestic garden food plants can be lower than 110 degrees F. That's the temp of the leaves, not the ambient. Say goodbye to corn, okra, etc.

[orthoclad]

6. Greater CO2 concentrations also change plant communities

Some types of photosynthesis saturate below 350 ppm, other types of photosynthesis take advantage of the higher concentration - like poison ivy. Food crops will be outcompeted by weeds; ecosystems are altering. We're disrupting primary production. This is happening globally, not just in hot environments.

The field of study is plant physiological ecology.