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Geothermal Taproot?

Tentatively I enter a realm of science in which I have no expertise
  [vote for,

Possibly MFD bad science... trying to avoid magic here. I wonder if it would be possible to genetically modify a tree with a long taproot, such as the mango tree, to use the root to draw up geothermal heat (as in, more heat than they currently get from the water and nutrients down there), possibly by growing roots that grow very deep down, deeper than is necessary for nutrients, in search solely of heat.

The goal I had in mind was to plant forests of these trees in places that are home to migratory birds so they don't have to migrate south for the winter to forests that are declining due to logging operations. A forest of heat-emanating trees would develop its own ecosystem in which the birds would thrive so they don't have to go south for the winter. This would reduce, in part, the damage caused by deforestation in the warmer climates that they migrate to.

If it's MFD, it's MFD. I get it. What do you guys think?

21 Quest, Nov 19 2011

Geothermal Energy http://www.mpoweruk...othermal_energy.htm
Pretty deep [csea, Nov 19 2011]

Not that deep... http://en.wikipedia...eothermal_heat_pump
//Depending on latitude, the temperature beneath the upper 6 metres (20 ft) of Earth's surface maintains a nearly constant temperature between 10 and 16 °C (50 and 60 °F)// [21 Quest, Nov 19 2011]


       I think it could be done, using GM maple trees that not only have the suggested heat-seeking taproot, but also an internal plumbing system to circulate the heated maple syrup. If the leaves could somehow be metallic, they may serve as better fins.
swimswim, Nov 19 2011

       This idea was played with in one of SF writer David Brin's books. I think it was "Startide Rising". These trees were found on an abandoned alien world and puzzled the biologists mightily as it was an 'all or nothing' strategy by the trees which couldn't have evolved naturally and incrementally.
AusCan531, Nov 19 2011

       Hmm... I wonder if it could be done by 'tweaking' the phototropism exhibited by many plants. The roots, of course, aren't phototropic, but perhaps they could be made so. And If they could be made phototropic, perhaps they could be made thermotropic, causing them to grow deeper and deeper.
21 Quest, Nov 19 2011

       I'm pretty sure the depths required to reach suitable temperatures exceed any reasonable guess as to possible taproot depth. [link]

       Hmm, I see you're just suggesting to keep the tree above freezing temperature.
csea, Nov 19 2011

       I think a lot depends on what you mean by "geothermal energy".

       Surface temperatures fluctuate seasonally, and the top few inches of soil follow them, so there's nothing there.

       A few feet further down, soil temperatures are a pretty stable average of the year-round temperature, so there's some excess energy available in winter (but also an energy drain in summer). I guess all deep-rooted plants in areas with harsh winters benefit from this to an extent.

       Further still, the ground temperature is averaged out over longer periods (over the last few years, the last few decades, centuries, millennia...) as you go deeper, so there might be some residual heat from a previous warmer climate.

       All this heat is just stored atmospheric heat.

       Deeper yet, and the temperature rises (regardless of local climate history) because of true geogenic energy coming from radioactive stuff decaying. So this is the only depth at which you can really get "new" energy as opposed to stored climate heat.

       The problem is, though, that very little biology is able to harvest heat energy. Biology is very good at adapting to the local temperature (to facilitate reactions), but I don't see how it generally harvests heat energy.

       For one thing, you need a thermal gradient to benefit from heat energy. You also need an efficient heat-pipe to let that gradient cause a rapid heat flow. I don't see how a tree, even if its roots are hotter than its crown, can transport enough thermal energy to be useful. Sap moves so slowly that hot sap from the roots is going to simply equilibrate little by little with its surroundings as it rises; there's never going to be a big and sudden exchange of heat that will be useful.

       So, I don't see how you're going to do anything useful this way. Yes, trees can (and perhaps could more so) benefit from having their roots in warm soil (or even, in theory, in rock which was hot from geothermal energy), but their crowns still have to grow in the local climate.

       So, a mango tree isn't going to thrive if its roots are warm and its crown is cold; it can't pump up enough heat (in sap or whatever) to keep the leaves warm (they have a huge surface area). In fact, it's going to be harder for a plant like this, because it has to have one set of enzymes in its roots (where they're warm) and a different set optimised for the local climate in its leaves.

       And the birds themselves - they are adapted largely to the relevant climate, and simply extending the range of mango trees isn't necessarily going to solve the problem - there's insects and water availability and all that stuff to think about.

       So, if you want to use geothermal energy to create forests of tropical trees further from the equator, I think your only hope would be to dig down and harvest the energy with huge heatpipes (steam geysers or whatever) and use that heat to warm the local climate. But there may be some complications with that idea too.
MaxwellBuchanan, Nov 19 2011

       The roots should only need to go down 20-30 feet to absorb enough heat to keep the tree's temperature above freezing. Given the typical length ratio of taproot to plant, a 30-40 tree should generate a taproot at least that long.

       Edit: after reading Maxwell's annotation, I realize that my own assumptions may be a little... off.
21 Quest, Nov 19 2011

       I guess our annotations overlapped. But do you know how much energy has to be pumped up from a groundsource to keep the leaves above ambient temperature? It'll be a huge amount, because leaves are flat. I don't see any way to pump heat that quickly from the ground to the leaves, unless you're talking about a fraction of a degree of temperature increase.

       Even then, heat energy will dissipate from the warmed leaves way faster than it can be transported through rocks to the roots. You're trying to balance the heat flux at the surface of a thousand big, flat leaves in air which can convect, against the heat flux through a smaller area of rock surrounding the roots.

       Even then, even if this heat flux could keep the leaves a degree warmer (and I'd guess 0.1°C would be the real limit), what happens when it rains or snows, and the thermal energy being carried away from the leaves increases by a factor of 10 or 100?

       The problem is not one of heat availability, it's one of heat transport. If you really want to stop the leaves freezing, you need to evolve frost- tolerant leaves (doable), or figure out a way to temporarily raise metabolic rates in the leaves to generate heat locally in times of cold.

       [OK, we've got overalapping annos, so I'll go away for a bit until we get back in synch.]
MaxwellBuchanan, Nov 19 2011

       (Way out of my depth on the subject!)

       Even if a suitable temperature gradient were available, wouldn't the relative heat transfer ratios (earth/root) vs. (leaves/air) cause this to be extremely inefficient?

       {I see [MB] beat me to the same conclusion by a few minutes...}
csea, Nov 19 2011

       Yes, if you're talking about a tree with flat leaves. I used the mango tree as an example of a tree with a long taproot, bit of a red herring. Sorry. What about conifers with much more narrow leaves, such a juniper?
21 Quest, Nov 19 2011

       I dunno - I think that even then the heat loss would far outrun the heat transfer.

       For conifer needles, imagine all the needles joined end-to-end. Now imagine the roots joined end-to-end. One is going to be much longer, and have a larger surface area, than the other.

       You'd be best off with some sort of succulent (large volume to surface area). Even then, though, I don't think you could do it with any non- spherical plant of a reasonable size - better to raise the metabolic rate in the leaves and generate the heat locally.

       If you *really* wanted to do this, you would have to use chemical harvesting and then release of the energy. So, you have a reaction in which A+B is in equilibrium with AB, and where increasing temperature shifts the reaction more towards AB.

       You pump A+B down to the roots, and then (and only then) expose them to an enzyme which will allow them to quickly reach equilibrium with AB.

       Then you pump the AB (plus residual A+B) up to the leaves, where the temperature favours the A+B side of the reaction. Then (and only then) do you expose them to the enzyme again, allowing AB to break down quickly into mostly A+B, releasing the heat. Then you repeat.

       In other words, you could transport the energy with less loss if you use a shifting chemical equilibrium facilitated by local enzymes, than if you transport it directly as heat. It also means you could store AB in the leaves (without enzyme) for some time, against frost. What you're doing, really, is restricting the heat exchange to the two relevant areas (roots, leaves).

       But I still don't think it'll work.
MaxwellBuchanan, Nov 19 2011

       Inducing drastic climate change to allow unfettered continuation of mass deforestation. Smart.
Alterother, Nov 20 2011

       The deforestation is already happening, and will continue to happen regardless of the plight of the wildlife being displaced. This is Plan B.
21 Quest, Nov 20 2011

       It's always good to have a Plan B, even if it's a horrible plan.
Alterother, Nov 21 2011

BunsenHoneydew, Nov 21 2011

       I keep reading this as "geothermal teapot", which is probably another idea.
MaxwellBuchanan, Nov 21 2011


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