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Earth Science

Trees' Leaves Grow At a Cool 70° All Over the World 537

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

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  • by Anonymous Coward on Thursday June 19, 2008 @04:55PM (#23864401)
    That's insane, that's so hot we'd burn our fingers if we touched the trees?!
  • by LighterShadeOfBlack ( 1011407 ) on Thursday June 19, 2008 @04:56PM (#23864409) Homepage
    That's 21C for anyone living in the 21st century.
  • Since I can't read the article, I'll speculate wildly. I've often wondered why chlorophyll isn't black for maximum sunlight absorption. The impression I get from the paragraph of the article that I can read without paying for it is that leaves maintain the optimum temperature for photosynthesis. Is green perhaps the easiest color to manufacture that will keep the leaves at the right temperature, even in full sunlight? That would explain why green was selected over other colors despite the fact that it's ref
    • Re: (Score:3, Insightful)

      by Otter ( 3800 )
      Since I can't read the article, I'll speculate wildly. I've often wondered why chlorophyll isn't black for maximum sunlight absorption.

      I'd imagine that the range of structures that can produce chlorophyll-like function is constrained, and that such structures with broader absorption either aren't possible or aren't evolutionarily reachable.

      • by postglock ( 917809 ) on Thursday June 19, 2008 @06:55PM (#23866285)
        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.

    • The green is reflected. Red and blue are absorbed. Why plants are green []
  • That's about 21.11 degrees Celsius.

    Americans really need to start using the metric system. Honestly, it really is worth the effort to switch.
    • Re: (Score:3, Insightful)

      Obviously not.
    • Re:Or in Celsius (Score:4, Insightful)

      by bucky0 ( 229117 ) on Thursday June 19, 2008 @05:07PM (#23864597)
      >Honestly, it really is worth the effort to switch.

      Really? I'm a physicist and spend all my professional time working in m/s/kg units, but outside of that, what does it matter? We changed over the easier things, but the bit that's left (espcially feet/inches) don't justify the amount it would cost us to retool everything to use metric.

      I never did get the obsession other people have with the units we use in the states.
      • Re:Or in Celsius (Score:5, Insightful)

        by Applekid ( 993327 ) on Thursday June 19, 2008 @05:21PM (#23864853)

        I never did get the obsession other people have with the units we use in the states.
        It's merely a point of contention for the "we're right, you're wrong" nationalistic crowd. Same with dates: MM/DD/YYYY, DD-MM-YYYY, YYYY.MM.DD, so on and so on.

        I'm sure a war or two has been fought over whether toilet paper should be hung in the proper overhand fashion or the grotesque underhand abomination.
      • Re:Or in Celsius (Score:5, Insightful)

        by vajaradakini ( 1209944 ) on Thursday June 19, 2008 @05:36PM (#23865089)
        Yes, clearly everything runs smoothly when people work in different units. Nothing could ever go wrong. Nobody could spend millions on a probe only to smash it into a planet instead, right? []

        Sometimes it's worth an inconvenience...
      • Re:Or in Celsius (Score:4, Insightful)

        by Anonymous Coward on Thursday June 19, 2008 @05:40PM (#23865145)
        Because it makes it very difficult to communicate things like that with Americans. How would you like it if you did a lot of business with Europe, but they still used cartwheels, furlongs, leagues, and all that stuff? The problem is communication. The rest of the world has seen value in the metric system and switched. But we have a huge problem in a very large country refuses to switch, necessitating the need to artificially extend the life of an archaic system of units.

        And for the record, I'm Canadian, living in the US. I STILL haven't gotten a feel for American units, but I'm getting a little better at doing the conversions in my head. That being said, I had no idea what 70F was until googling it.
        • Re:Or in Celsius (Score:5, Insightful)

          by NotBornYesterday ( 1093817 ) * on Thursday June 19, 2008 @06:48PM (#23866179) Journal
          We buy our milk in gallon jugs, but our soda in 2-liter bottles. However, if you buy soda in quantities less than 1 liter, the measurements switch over to ounces. Every ruler/tape measure/etc. I have had for the past 30 years has been dual-marked with inches and centimeters. Our toilets and urinals are marked "1 gallon / 3.8 liters per flush", and our speedometers are marked in both mph and kph. Engine displacement on new vehicles is noted in liters, while engine displacement on older muscle cars is still noted in cubic inches (as it should be). I have a socket wrench set that includes english and metric sockets.

          So, we've been doing pretty well working with both at the same time for years. You mean to say the rest of the world can't keep up? ;)

          • Re: (Score:3, Insightful)

            by eloki ( 29152 )
            I'm Australian, and I think it's just another one of those things where the size/dominance of the US is annoying to the rest of the world because it is different *and gets away with it*.

            We've all converted to metric but the US refuses the change. That's partly understandable due to the cost/effort, but it means that the rest of the world forever more has to convert units to talk to them. Effectively they're making more work for everyone, and don't seem to care. When you think about it, in many social situat
        • Re:Or in Celsius (Score:5, Interesting)

          by argStyopa ( 232550 ) on Friday June 20, 2008 @10:58AM (#23873373) Journal

          Again, for those not paying attention: precision has not always equaled utility.

          1) the Imperial measures are far more human-friendly than metric. Metric is WONDERFUL in a computer-driven world, but for everyday measures, a number of imperial systems are much more practical:
                    a) Temperature: Fahrenheit based his temperatures on a likely-to-be-experienced-by-people scale. Since he was in Copenhagen, this meant typically 0-100. Humans don't really care about precise temps, so the greater precision of Fahrenheit is meaningless, it just suits human penchant for round numbers. (FWIW, Celsius *did* originally arrange his system in reverse, with water freezing at 100 and boiling at 0...)
                    b) linear: again, for the bulk of human history, utility has NOT been measured by decimals, but by simple calculation. The foot, divided into 12 subunits (each, conveniently for a carpenter, about a male thumb-width), is (integer) divisible by 12, 6, 4, 3, 2, and 1. The larger unit of a yard (~1m) is integer divisible by 36, 18, 12, 9, 6, 4, 3, 2, and 1. Decimals, on the other hand, are divisible by 10, 5, 2, and 1. Certainly, large maths are much more easily worked in metric measures, but again, in typical parlance, humans don't use large maths when they don't have to - we don't measure soccer fields in mm, for example.

          As far as American usage is concerned, it's already been stated: US citizens have routinely and widely switched to SI units for anything that matters. I work in logistics, and am routinely converting from cubic inches to cbm, from lbs to metric tons, etc. No big deal - but for some reason the REST of the world feels entitled to complain about what units WE use? I genuinely don't get that. Do Americans get to complain that Egyptians speak Egyptian, because it makes it harder for us to do business in Egypt? I don't think so.

          And for the snide comments about the unit-conversion causing the loss of a Mars probe...well, at least we're a technologically-successful-enough state that we're tossing probes at Mars, despite our "imperial units handicap"....
          According to [], there have been 43 missions to Mars, 20 by the 'benighted' Americans, and 23 by other nations presumably not hobbled by their attachment to an archaic system of measures.
          American success rate is running at 70%.
          "Other" success rate is running at just over 30%, depending on how you count it.
          Perhaps you guys should try Imperial measures? Maybe that might work better?

      • by geekoid ( 135745 )
        We where going to be metric by now, but Reagan killed it.

        I think global standards are good, and more important the more connected we get.
        Retooling would be the cost it was in the 70's and 80s. Many factories produce both already.

        OTOH, it's not worth the pissing match.
        I notice England doesn't get a lot of crap over it's Pints.
    • Re:Or in Celsius (Score:5, Insightful)

      by Pennidren ( 1211474 ) on Thursday June 19, 2008 @07:52PM (#23866933)
      The rest of the world really needs to start using only English. Honestly, it really is worth the effort to switch.
    • Re:Or in Celsius (Score:5, Insightful)

      by Andrew_T366 ( 759304 ) on Thursday June 19, 2008 @10:41PM (#23868289)

      I'm generally in favor of metrication and the use of metric units, but the issue of temperature is a key exception. The Fahrenheit scale is more precise, and its zero-to-100 degree range more realistically covers the spectrum of what one would typically see on a weather report.

      I sometimes wonder why Celsius is considered a metric measure to begin with: It predates the advent of the modern metric system itself. Its zero-degree reference point is just as arbitrary as Fahrenheit's in the big scheme of things. And, the measure doesn't employ metric prefixes (although I suppose they could conceivably be appropriated for the purpose).

      • Re: (Score:3, Insightful)

        by teh kurisu ( 701097 )

        I disagree, it's quite useful on a weather report to be able to communicate easily what side of freezing the temperature is. It's not arbitrary when it means potentially hazardous road conditions, or the need to leave the heating on low to prevent the pipes from freezing.

  • by MollyB ( 162595 ) * on Thursday June 19, 2008 @05:06PM (#23864573) Journal
    The first link is to a subscription-only site.
    The second contains "warm" and fuzzy quotes like the following:
    "Trees in chilly climates also have ways to make their leaves or needles retain more heat from the sun. Pine needles, for example, clump together. Think of gloves and mittens, Helliker says. If you're wearing gloves, wind can easily whip heat away from your individual fingers, leaving you cold. But if your fingers are all together in a mitten, they're going to be warmer.

    Richter says the discovery isn't just fascinating science. It gives her a special kinship with trees.

    On a recent day in Philadelphia when the mercury was near 100 degrees, she said, "I was staring at a hickory tree and its leaves were down â" they had wilted," she says. "And I was thinking, hey, it's hot, I'm hot. They enjoy 70 degrees, and I enjoy 70 degrees, too.""

    A special kinship with trees?!? How did this make it to Nature?
    • Jesus F Christ (Score:4, Interesting)

      by Moraelin ( 679338 ) on Thursday June 19, 2008 @06:11PM (#23865677) Journal
      Jesus F Christ, forget the kinship. The quote about pine needles is just about the most retarded thing I've heard in ages.

      Having lots of thin needles near each other is actually a pretty good heatsink design. No, seriously. Not as good as some ducted designs, and not as cheap to make as shaved copper fins, but nevertheless, if you're going to blow air through it, it gets heat out rather impressively well. Per weight, it has a _lot_ of surface to exchange heat through.

      Evergreens don't "stay warm like fingers in a mitten" in winter, but, among other things, have one or more of the following reasons for what they are:

      1. The needles allow the snow to fall off the trees easier than a broad leaf. (But not all evergreens have needles, btw.)

      2. Many contain chemicals that act, effectively, like anti-freeze. You can't stay warm like fingers in a mitten when you can't produce your own warmth. Your fingers stay warm in a mitten just because they produce their own heat, and the mitten keeps it in. If you were cold blooded, like a tree, even keeping them tight together and even a mitten wouldn't last you all winter. The best you can do is try not to freeze as early.

      But even so, they're photosynthesizing a lot slower in winter, and when the temperature drops enough and that water freezes anyway, not at all.

      3. They grow in areas with less sunlight, warmth and soil nutrients, so they can't afford to just lose the leaves and consume nutrients to make more in spring. So even if temperature drops enough that they do freeze, they keep their leaves because they can't afford to just drop them all and make a new batch later. They keep their needles for _years_.

      4. The thick needles and waxy cover help conserve water. Basically they try to lose as little as possible, among other things, because #2 and because getting more from the ground is a pain in winter anyway.

      So, seriously, this looks to me like the most retarded kind of pseudo-science. The kind that just imagines some fairy-tale explanation. Worse yet, one based on little more than anthropomorphizing the damn trees.
  • run your house cooling lines right into the trunk baby....

    70 degrees sounds kinda sweet-- better than running the rods 150 feet underground...

  • by sidnelson13 ( 1309391 ) on Thursday June 19, 2008 @05:16PM (#23864789)

    ... when placed into moist locations. Give me five!

    Ok, no good comes from watching Scrubs.

  • by booch ( 4157 ) * <slashdot2010@cra ... m ['ek.' in gap]> on Thursday June 19, 2008 @05:52PM (#23865331) Homepage
    I've often wondered why it is that humans prefer air temperatures somewhere around 72Â. It'd seem more reasonable for us to prefer something closer to 98Â. I suppose the temperature differential between the 2 is what's required to keep us at a steady state, dissipating the energy we burn.

    I find it even more remarkable that trees prefer nearly the same temperature that humans do.
    • by booch ( 4157 ) *
      OK, who changed my degree symbols into hatted A's (Â)? I actually cut and pasted the degree symbol from the article title. That doesn't work, nor does &#176; or &deg;.

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