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I've just finished reading The Hidden Lives of Trees by Peter Wohlleben, which I thoroughly enjoyed.

According to the author, the advantage of shaking the leaves is that both sides of the leaf are exposed to the sun, and therefore both sides can photosynthesize. This would be in contrast to other species, where the underside is reserved for breathing and transpiring. However, to me (a complete amateur), the underside of a quaking aspen seems paler in colour and doesn't "look" like it's any more suited to photosynthesis than the underside of any other leaf.

In addition, I can't find any other sources that back this claim. Most other sources (for example https://www.nature.com/scitable/knowledge/library/case-study-the-glorious-golden-and-gigantic-13261308/) seem to claim the shaking of the leaves reduces the risks that come with too much sunlight, which damages the leaves and actually lowers the rate of photosynthesis.

My question is therefore, what is the most convincing advantage the quaking aspen gains from this characteristic ?

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    $\begingroup$ I would have to ask whether there is in fact any particular advantage, and indeed, whether aspens "quake" much more than other broad-leafed trees. My casual observation is that they really don't, it's just that they're often the only deciduous tree in areas with conifer forests, so the leaf movement stands out. $\endgroup$
    – jamesqf
    Mar 25, 2020 at 16:59
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    $\begingroup$ Quaking aspens do indeed "quake" in the merest of breezes, but aspen leaves are very light compared to maple or oak leaves and ave a flat petiole, another surface to catch the breeze. Maybe there is no benefit, it just is what it is. It's not like they attract other trees this way. $\endgroup$ Mar 26, 2020 at 0:18
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    $\begingroup$ Hmm "why" do they quake? Impossible to know. The best the scientific process can do is determine if quaking provides any physiological or ecological advantages to the trees. I do not know of any specific research examining this (not too unusual) "phenomenon" in quaking aspen, but I'll dig around to see if I can find any interesting papers for you... $\endgroup$ Mar 27, 2020 at 6:05
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    $\begingroup$ Conjecturally: P. tremuloides is an early successional (i.e.,"foundational") species, and as a result is typically going to be exposed to more sunlight (due to less other plants shading them out). Their foundational role also means they use more of their energy to develop fast-growing foliage to out-compete other plants for sun (and therefore have less energy for developing UV defenses). I would guess that the added heat of the direct sun and less robust UV protection would decrease fitness, and so the plant would benefit from having less horizontal and still leaves. Natural selection etc.. $\endgroup$ Mar 27, 2020 at 6:15
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    $\begingroup$ Robberecht & Caldwell (1978) demonstrate that P. tremuloides experiences substantial UV protection from epidermal compounds. However, this could be interpreted in 2 ways relative to my previous comment. 1) reaffirming the need for and past evolution of traits to protect against high UV (which we know is common in its habitat). Or 2) no need for additional UV protection due to having adequate epidermal protection -- therefore reducing the odds of UV damage being the selective driver for quaking. Heat is still an issue though... $\endgroup$ Mar 27, 2020 at 6:31

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Possible reasons evolution has created leaves that “quake”: keep insects off, cool off, reduce wind load, keep birds and squirrels away, create sound or vibration within the tree to stimulate growth.

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    $\begingroup$ Welcome to Biology.SE. This looks very speculative, which is explicitly off-topic for this site (we want fact based answers). In addition, answers are much more likely to receive a favorable response if they include supporting references (primary literature is best). This is a good example of how to format references. As it is, your answer is indistinguishable from opinion and thus inappropriate for this site. ——— Please take the tour and consult the help center pages for additional advice on How to Answer and How to Ask effectively on this site. $\endgroup$
    – tyersome
    Aug 9 at 0:29

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