Trees' Leaves Grow At a Cool 70° All Over the World

biogeochick writes "Ever turn on the air conditioner on a hot day? How about a heater when it gets cold? OK, so we all know that humans act to keep themselves cool, but what about trees? A recent article on tree core isotopic evidence has shown that trees from tropical to boreal forests all grow at 70 degrees. The study, published in Nature by some fantastic researchers (so one of them is my adviser, so sue me) and covered by NPR on All Things Considered, has shed some light on the convergent temperature at which trees perform photosynthesis." Update: 06/19 21:31 GMT by T : I give, I give -- that's 70 degrees Fahrenheit.

Shameless karma whore

[LighterShadeOfBlack]

That's 21C for anyone living in the 21st century.

Re:Shameless karma whore

[evdubs]

Uhh.. no it isn't. According to wikipedia [wikipedia.org], there are three "standard" temperatures you can use to calibrate your thermometer for a Fahrenheit scale.

1) 0F - the stable temperature of ice, water, and NH_4Cl
2) 32F - where water freezes
3) 96F - average body temperature

Alcohol is not used anywhere.

Hey, I can understand units, but don't mess

[DRAGONWEEZEL]

with hanging toilet paper! It's over the top, Like it or not! Allways and everywhere unless your some kind of freaking psychopath!

Re:pretty thin science...

[philspear]

A special kinship with trees?!? How did this make it to Nature?

It didn't, it made it into NPR.

The abstract for the nature article:

The oxygen isotope ratio (18O) of cellulose is thought to provide a record of ambient temperature and relative humidity during periods of carbon assimilation1, 2. Here we introduce a method to resolve tree-canopy leaf temperature with the use of 18O of cellulose in 39 tree species. We show a remarkably constant leaf temperature of 21.4 2.2 C across 50 of latitude, from subtropical to boreal biomes. This means that when carbon assimilation is maximal, the physiological and morphological properties of tree branches serve to raise leaf temperature above air temperature to a much greater extent in more northern latitudes. A main assumption underlying the use of 18O to reconstruct climate history is that the temperature and relative humidity of an actively photosynthesizing leaf are the same as those of the surrounding air3, 4. Our data are contrary to that assumption and show that plant physiological ecology must be considered when reconstructing climate through isotope analysis. Furthermore, our results may explain why climate has only a modest effect on leaf economic traits5 in general.

So it made it into Nature because their results challenge an apperantly widely held assumption used in determining global warming... I think? I'm no ecologist/arborologist/whatever science is involved here. But it's actual science.

Re:Shameless karma whore

[flyingfsck]

You know, even a ship does better than that I think, that is about 10 feet per gallon.

Re:Why are plants green?

[solanum]

Mod parent down. This is absolute rubbish, how did it get to +5 informative? I assume it's there as a joke so it should only be +5 funny, or possibly now, +5 fooled Slashdot. I am a plant physiologist, there are three basic types of chlorophyll in land plants, a,b & c. They have slightly different spectra, but they are not blue and yellow, they all have minimal absorbance in the green part of the spectrum and thus look green. The yellows and reds in senescing leaves are from carotenoids and anthocyanins.

Re:Why are plants green?

[postglock]

The green colour of chlorophyll relates to the historical precursors to the first photosynthetic organisms. Originally (a few billion years ago), early bacteria were non-photosynthetic, fermenting carbon anaerobically. This rapidly depleted the primordial "soup." The first organisms to utilise light (something akin to Halobacterium halobium) used a pigment called bacteriorhodopsin to help its metabolism. Bacteriorhodopsin absorbs a central band of visible light.

The evolution of chlorophyll followed (perhaps in Cyanobacteria) in organisms at the bottom of the sea. These were the first organisms to fix carbon dioxide. Being at the bottom of the ocean, only the far bands of visible light were available to them (blue and red), and hence green chlorophyll evolved.

Since then, accessory pigments have also evolved (e.g. phycobiliproteins), which have reclaimed other parts of the visible spectrum, and changed the colour of the plants or algae.

Re:Shameless karma whore

[jc42]

Since when was normal body temp 96F? Google-sama tell me it's 98.6F.

Except that that .6 is bogus precision. The "normal" core temperature of a healthy human body varies by a degree or two over the course of a day without any harm. Attempts to calculate an average temperature of a crowd of humans will turn out different in the third decimal place depending on which humans and which measuring tools you use.

The conventional 98.6F temperature comes from converting 37C to Fahrenheit. The 37C temperature is also "plus or minus a degree or so", but it doesn't have fake precision from a third digit.

98F and 99F are completely normal temperatures for a human body, and are no cause for medical alarm. The .6 is a meaningless artifact of conversion from Celsius.

96F would produce a mildly worried look on your doctor's face, though it wouldn't result in a panic.

Similarly, I once registered 101 point something on a doctor's thermometer, and he just asked me what I'd been doing in the previous hour. I told him that I'd been playing tennis and had a hot shower. He just nodded, and went on to other things, since I'd explained the slightly elevated temperature. He did take my temperature again 10 or 15 minutes later, and when it was lower, he ignored it.

Re:Shameless karma whore

[rocketPack]

The parent is not kidding:
40 rods = 0.125miles
1 hogshead = 63 U.S. Gallons
So... ((0.125miles)*5280ft/mi)/63 gallons=10.476 feet per gallon

GP must drive a Hummer... perhaps only in reverse, like Mother Goose.

Re:Or in Celsius

[maglor_83]

Not quite. -40 is the convergence point

Re:Or in Celsius

[Strange Ranger]

Hanging toilet paper over the top has no benefit except to make the foldy triangle look nice in hotel rooms.
It's actually a pain because when you go to tear some off with one hand you have to be quick and nimble to keep the paper from spooling out all over the place.

Hanging it under is far more practical. You can tear if it off with one hand very easily without having the paper unspool 7 yards of itself onto the floor.

Hang it under.

Re:Shameless karma whore

[Simon Brooke]

And that's why an American paper should be using the metric system? Because the 95% of the world that's not in America is too stupid to realize that it's an American publication writing to an American audience using the units of measure in use in America?

Errrrr... hate to tell you this, but the journal in question is Nature. Published by Macmillan Publishers Ltd, a British company owned by a German group, for an international audience.

Re:Shameless karma whore

[pjt33]

Major scientific journals are not written for "an American audience" but for an international audience. But this is a total red herring anyway, because if you RTFA you'll find that it uses centigrade.

Re:Or in Celsius

[colenski]

Commercial and military aviators seem to think so.

Re:Get a real unit.

[Anonymous Coward]

If I recall my chemistry correctly, I think you mean 70 Kelvin, the Kelvin scale does not use degrees.

Well, that depends on how old you are. "Degrees Kelvin" was acceptable usage until 1968 when an arbitrary meeting of arbitrary guys decided, arbitrarily, that it would no longer be proper usage.

Re:Shameless karma whore

[bloobloo]

Because "In accordance with various Federal Acts, the Code of Federal Regulations, and Executive Order 12770 (see Preface), it is NIST policy that the SI shall be used in all NIST publications. "

http://physics.nist.gov/Pubs/SP811/sec02.html [nist.gov]

It is...

[msauve]

"degree Rankine [nist.gov]", same as "degree Celcius," "degree centigrade," and "degree Fahrenheit." Kelvin is the odd man out.

Re:US Units

[Anonymous Coward]

No; despite the Wikipedian oracle's attempt to change it by fiat, the stone remains a unit of weight. As the pound, in terms of which the oracle defines the stone. Both predate the concept of mass, and in normal English usage can only be used as units of weight. If you read the relevant Wikipedia articles carefully, and have ever studied physics, you'll notice that they imply that the pound is a unit of both weight and mass (even having two separate articles, one for the "pound (mass)" and one for the "pound (weight)", which any engineering professor will tell you is rubbish. Fortunately, they do mention the correct, if contrived and inelegant, 'pound-mass' as a synonym for this supposed sense of 'pound'. They avoid the slug and its relation to the pound altogether in those articles, because that would make clear their pretense.

Re:Shameless karma whore

[rossdee]

I think it was meant to be related to the circumference of the earth, going around the poles, and passing through Paris (since it was invented by the French) I think they werent aware of the amount of oblateness the earth had, so they got it wrong. They then decided it was to be 'the length of a bar of platinum, in some vault in Paris) since they didnt want to redefine not just the metre, but all the derived units. Nowdays of course it is defined based on some wavelength of light (in a particular atomic reaction or something, just like the second.

Re:Get a real unit.

[jc42]

I think you mean 70 Kelvin, the Kelvin scale does not use degrees.

Actually, it does, but it uses the Celsius degree. The term "Kelvin" unit is defined as "degrees Celsius above absolute zero". So a phrase like "70 degrees Kelvin" expands to "70 degrees degrees Kelvin above absolute zero". This isn't so much wrong as silly (at least to someone who knows the definition).

It's the same sort of error as saying "PIN number", which expands to "Personal Identification Number number". It's easy to understand why someone who doesn't understand the term might say something like this. But in both cases, saying such things just makes you sound ignorant of the term's meaning.

There are lots of technical terms what are used incorrectly in this fashion. Maybe others will post their favorites ...

Re:Shameless karma whore

[ceoyoyo]

Yes, when you're buying crack. ;)

Re:Shameless karma whore

[Simon Brooke]

Which is another way of saying 'less than 5% of the population of the world still uses Fahrenheit'.

It's also another way of saying:
'More than 75% of native English speakers use Fahrenheit'.
'Almost 66% of fluent English speakers use Fahrenheit'.
'About 50% of all Internet users (any language) use Fahrenheit'.

I see that as well as not teaching standard units in American schools, they also don't teach basic arithmetic.

• The US has 304 million people, the UK 60, South Africa 47, Canada 33, Australia 21. None of these countries are entirely native English speaking, of course, but many other countries have substantial English-speaking minorities. Only 215 million Americans have English as their first language. Over all, fewer than 70% of the world's native English speakers, and fewer than 30% of the world's fluent English speakers, live in the US.
• Slitly fewer than one and a half thousand million people use the Internet [internetworldstats.com], of whom fewer than two hundred anf fifty million are in the US. Therefore US Internet users make up 17.5% of Internet users

Of course, the US isn't the only country in the world still to use Fahrenheit. There's also Belize [wikipedia.org].

Re:Get a real unit.

[sznupi]

No, kelvin is defined as 1/273,16 of the difference between absolute zero and triple point of water. This definition does mean that 1 K increment has the same magnitude as 1 Celsius degree increment, but it isn't defined by it.