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[KodKod]

Now if the thread's title was 'Nether Caps - Chloroform of the Caverns', that would be something to get excited about.

[Xnidus]

If the nether caps can include "candy" atoms in their tissues like the "iron snail"?. They can explain their magma-safe properties ("candy" atoms in a complex organic tissue) and the ability to be burned into ash or charcoal (organical material) at the same time.

Yes, the "candy" is rare, but we can discover "candy" in every map (and in the last fort I discover a "candy" spike in middle of the caverns!, inside the spike, the "circus"... oh, dam...). And is the only metal that are distributed everywhere on the world. Also is the only metal with really unreal characteristics. Perhaps nether caps have a miniature nuclear reactor in the core and the "candy" is part of the refrigeration system.

Mmm, I'm crazy?

[Hotaru]

Um, I don't see an ecosystem being down there as impossible. The caverns ARE open to the surface after all, and real world cave ecosystems exist.

Spoiler (click to show/hide)

Cave ecosystems are mainly sustained by things washed/brought down into the underdark from above. It's also known that various bacteria exist even in the very deep stone, inside rocks as endoliths, and chemosynthetic processes (most probably?) will provide for life. In the DF world there's also the underneath-the-underdark from which things like blood men and such are brought up for the cave ecosystem to feed on.

There's also a process called thermosynthesis which exists theoretically. Here a temperature gradient is used to power anabolic reactions in tissue. I would assume nether caps could use this reaction class to sustain life, if they've found a way to cool themselves. Since they're freezing temperature, yet the caves are not, and they won't freeze water there would have to be some process inside nether-cap tissue that makes it cool yet does not make it freeze.

Some insects can control water crystal formation to not freeze in subzero temperatures. The nether-cap has to do this too. One easy (if thermodynamically possible?) way in which they could cool their tissue is, if they have something like transporter molecules for individual water molecules in their surface layer by which they force water to evaporate even at low temperatures, causing a cooling reaction. Kind of like human sweating. If it's some kind of freaky antiporter molecule that uses something abundant in the caves and not products of the mushroom's own metabolism, the wood would stay cool for a while after death (in the cave) but if you exposed it to a lot of heat instantly, still burn.

As for the cave foliage, you would assume they either have some air-boundary reaction or it's a species only in the process of adaptation to the underworld. Maybe the wayward seeds of some aboveground plant that for some reason could thrive there. Or, it could be bulbs in inverse. As in: the soil is so teeming with hungry life compared to the air, the plant actually grows leaves for safe food storage. Which dwarves then eat.

[eugene]

Fungi do not necessarily have to be strictly heterotrophic (eating only nutrients produced by others). Also they might use light of another wavelengths. Possible example is this black mold in the cellar of Chernobyl.

http://en.wikipedia.org/wiki/Radiotrophic_fungus

 I don't think it would work in real life with infrared radiation as those photon are not energetic enough to break up most chemical bonds. Anyway I love the idea and consider this a valid hypothesis for dwarven science.

[Rolan7]

I wish I remember more from organic chemistry class ):  Still, a plant that stays cold so close to the magma is exciting - it could power the entire underground ecosystem!

Nether caps absorb potentially huge amounts of heat.  They use this in endothermic reactions, putting the energy into atomic bonds.  Lets say they produce methane from carbon dioxide and water vapor, in a reverse combustion:
CO2 + 2 H2O + heat -> CH4 + 2 O2
This probably decreases local entropy like a mofo, and it also assumes that there is a lot of water vapor in the air, but I will explain later.
The nether caps also produce sugars to power their own metabolisms, like real life plants.  They have a lot of heat to work with.

This explains why:
Nether cap is cold.
There is oxygen that far underground.
The third cavern isn't unbearably hot.

However:
Where is the carbon dioxide coming from?
Where does the methane go?

The answer to both is the upper cavern layers!  All other below-ground plants (in DF) get their energy by combusting methane from nether caps.  The carbon dioxide released is reprocessed by the nether caps.

"But there are hundreds of meters of solid rock in the way!" Well, somehow there is breathable air throughout the underground, and I have a theory: On Halloween (when the candy was placed underground) it was done from space.  Trillions of threads of cotton candy fell through the earth, leaving incredibly tiny tubes in their trail.  These are everywhere, and watertight, but not fully airtight.  Therefore the underground has a (slow) air cycle.

The third cavern layer actually contains trace amounts of cotton candy which didn't fall properly.  In order to perform the entropically devastating reverse-combustion reaction, nether caps have to break these threads.  The massive entropy from removing even a single atom at a time is sufficient to sustain the reaction for some time, this loose candy won't become scarce for hundreds of thousands of years.

Edit: Excess methane burns up in the magma, keeping the system stable.  Quarry bush "leaves" are methane-collecting gills.  Methane-combusting plants don't get noticeably warm because their metabolisms stop just above the normal cave temperature - this is why the ground is the same temperature underneath a hot or cold biome.  Also their metabolisms are incredibly slow (until they're grown artificially).

[Nil Eyeglazed]

Um, I don't see an ecosystem being down there as impossible. The caverns ARE open to the surface after all, and real world cave ecosystems exist.

The issue with the cavern ecosystem isn't that it exists at all-- it's that it's capable of supporting a fortress of 200.

Consider a fortress walled off to both the caverns and the surface, 200 dwarves fed by 100 unfertilized farm tiles (400 sq m, lets call it).  Sure, some nutrients are going to diffuse.  But how much needs to diffuse?

Let's assume that dwarves need about 2000 kcal a day for their dietary needs.  If those needs are being met by mushrooms, then it's necessary for any kcal needs of the dwarves to be met or exceeded by the kcal requirements of the mushrooms.  In other words, our farm plot needs at least 134 million kcals every year.

How much mass does it take to deliver 134 million kcals?  Depends on your vehicle.  Let's assume its in the form of pure sugar.  That's 3.36 million grams of sugar needed every year, 33.6 metric tons of sugar over 400 sq m.

Every single day, a half a pound of sugar is diffusing over every square meter.  No wonder the bottom is made out of candy.

[Sadrice]

That process would certainly not be enthalpically (is that even a valid form of that word?) favored, but with some awesome candy chemistry, I suppose it could work.  Perhaps that process, instead of taking heat directly, converts heat into some sort of energy transport molecule, analogous to ATP, down deep in the roots where it has access to magma, and then performs the process up in the cooler cavern.  I imagine that, in a reaction producing methane, if you want to keep your methane around, you would not want it to be at magma temperatures.

Another possible reason for it to be cool is if, instead of methane, nether caps were making volatile liquid hydrocarbons, which are then somehow packaged up (maybe weakly polymerized, like sugars?) in the wood, and are slowly released from the dead wood, making it cold for quite a while after it's cut. 

As for farming, it's so ludicrously overproductive that it doesn't come remotely close to making sense, energetically.  Also, egglayers, or dogs, which deliver lots and lots of food with no energy input at all.

[psychologicalshock]

I am pretty sure plants are NOT endothermic because they absorb light (heat requires a physical collision, light can only be converted to it ) and then convert it into heat. If something is growing colder that means that it absorbs heat from the surroundings which implies a lowering of entropy within the surroundings. If this heat is used to lower the enthalpy (Internal energy + pdV) then the reaction is then spontaneous which implies that either the products of the reaction are more stable or the object is losing Volume. It's possible for living systems to do this if they're accomplishing a reaction that yields a large drop in internal energy; however, this is pretty slow because a reaction powered by collisions is limited in speed.

[psychologicalshock]

I wish I remember more from organic chemistry class ):  Still, a plant that stays cold so close to the magma is exciting - it could power the entire underground ecosystem!

Nether caps absorb potentially huge amounts of heat.  They use this in endothermic reactions, putting the energy into atomic bonds.  Lets say they produce methane from carbon dioxide and water vapor, in a reverse combustion:
CO2 + 2 H2O + heat -> CH4 + 2 O2
This probably decreases local entropy like a mofo, and it also assumes that there is a lot of water vapor in the air, but I will explain later.
The nether caps also produce sugars to power their own metabolisms, like real life plants.  They have a lot of heat to work with.

The reaction you offered is quite energetic in the reverse but forcing it to go the other way would take ungodly amounts of heat. The plant would likely use acids to reduce CO2 to CH4.

Remember that a reaction can only happen if the collision energy is enough to make it happen, if your environment is a cave it's unlikely you'll have any of your population of reagents develop the kind of energy to make  a reverse oxidation of methane happen because you just wont have any particles reach the energy states required.

Basically for it to happen in a cave it probably has to be a reaction that doesn't require a large input so it can keep sucking collision energy out of its environment without having to give much back. If you have to "develop" energy through multiple collisions it will be given back to its environment.

[Sadrice]

Heating because of energy coming in from the outside means nothing for whether a reaction is endothermic or not.  When calculating enthalpy, you usually try to minimize heat entering or leaving the system, with, say, a calorimeter, but of course you can't do that for photosynthesis.  Photosynthesis is in fact endothermic.  Chlorophyll absorbs one photon (which is not converted directly to heat, in this case), and loses an electron, which is passed through a complex chain of specialized pigments and enzymes, and is eventually used to pump protons into little sacs called thylakoids, building up a concentration gradient, which is then used to build simple sugars, not glucose, but G3P, a 3 carbon phosphate sugar which can be combined to make glucose, or put through various other reactions to build useful molecules.  The whole reaction involves some heating, because it's not 100% efficient, but it's absorbing energy and putting a large part of it into carbon-carbon bonds, which is pretty much by definition endothermic.  The leaf as a whole doesn't get hot because whenever photosynthesis is taking place, so is evapotranspiration which brings in water for photosynthesis while cooling the leaf (in most plants, there are some weird desert exceptions).  Too much heat can cause big problems for the photosynthesis reaction, so plants carefully regulate evapotranspiration to keep the leaf at appropriate temperatures, and if too much water is being lost and the stomata (little valves on the leaf surface) get closed, photosynthesis is usually turned off.

[BigFatStupidHead]

Hey folks, just an incredibly major mistake that a few of you are making here, fungi are NOT plants. They are actually more similar to animals than plants in all but the most superficial ways.

Also, they do not ever, under any circumstances, undergo photosyntheses.

Bio-nerd rant, deactivate.

[tahujdt]

What you're forgetting is that when we are taking something that isn't shown(nutrients), we are also leaving something that isn't shown(waste). Think about it. All of the egg shells from the overproductive turkeys, the rope reed husks, the stuff that the Cave Dragon (Tame) leaves behind, all of it fertilizing the gardens. For that matter, where doe the blood go after your dwarves clean it up? Right on the farm plot, most likely!

[psychologicalshock]

Heating because of energy coming in from the outside means nothing for whether a reaction is endothermic or not.  When calculating enthalpy, you usually try to minimize heat entering or leaving the system, with, say, a calorimeter, but of course you can't do that for photosynthesis.  Photosynthesis is in fact endothermic.

In thermodynamics, the word endothermic ("within-heating") describes a process or reaction in which the system absorbs energy from the surroundings in the form of heat.

Light is a form of work, not heat.

Chlorophyll absorbs one photon (which is not converted directly to heat, in this case), and loses an electron, which is passed through a complex chain of specialized pigments and enzymes, and is eventually used to pump protons into little sacs called thylakoids, building up a concentration gradient, which is then used to build simple sugars, not glucose, but G3P, a 3 carbon phosphate sugar which can be combined to make glucose, or put through various other reactions to build useful molecules.  The whole reaction involves some heating, because it's not 100% efficient, but it's absorbing energy and putting a large part of it into carbon-carbon bonds, which is pretty much by definition endothermic.

Except plants produce heat, like everything that is alive.

Plants convert one type of work into another at a loss of heat, but they do not absorb heat and convert it into work.

[Sadrice]

We know they're not plants (or at least I do, but I'm a botany student with an interest in mycology), we're discussing hypothetical autotrophic fungi because there has to be a base of the cavern food chain.  Real world cavern ecosystems generally don't have any (or many) producers, and run on the decomposition of organic waste that flows in from the surface, but real cavern ecosystems have an extremely limited biomass without some sort of vehicle bringing enormous amounts of food.  Bats do this, transporting energy from surface insects and fruit, and depositing it as guano.  But DF caverns don't seem to have many bats, or many connections to the surface that would provide the food for the ridiculous biomass present in them.  There has to be a primary producer somewhere in there, and the fungal forest seems like a likely suspect.

It's possible the fungus isn't doing this itself, and has a symbiotic relationship with some sort of autotrophic microorganism.  That's a historically very popular life strategy for fungi, and lichenized fungi are thought by some to have evolved at least 5 separate times (3 in ascomycota, 2 in basidiomycota), though other researchers believe that it's actually the ancestral strategy that was lost in the groups that don't have it, and may have only evolved once or twice.

Anyways, the photosynthesis discussion was more of a tangent than a claim that fungi have chloroplasts.

As for plants producing heat, yes they do, but that is mostly from respiration, where they turn the sugars they made from photosynthesis into useful energy, in the form of ATP, and not so useful energy, in the form of heat.  Using the ATP releases yet more heat.  I never claimed that plants convert heat into sugar, they take light, use the energy from it impacting a chlorophyll (which is in the form of an electron being elevated to a higher energy level, not heat energy), and then using that energized electron to drive the process.  Not all of the energy harvested from the photon is used, some is released as heat.  Endothermic does not necessarily mean "gets colder", it more often means that as the system absorbs energy from the environment, it does not heat up as much as it would if the endothermic reaction were not taking place.  I don't think we really disagree about what endothermic means, I think we're arguing past each other.


EDIT: found a lovely (though extremely simplified) reaction coordinate diagram of photosynthesis.  Notice that the line finishes at a higher point that it starts.

Spoiler (click to show/hide)

[runlvlzero]

Well there is a big precedent for real life rock eating bacteria and such that live at 7.5 miles beneath the earth in temps of 200-380 Fahrenheit. (the Russians drilled a big hole and pulled up rock samples with the buggers in there. There's tons of very sciency white papers on it...

I don't know why biomass and biodiversity isn't greater, its certainly there though (in real life). Its just more like a desert then a lush verdant jungle underground. I don't know what causes some ecosystems to be rich in macroscopic life vs microscopic. Maybe something happened, in dwarf reality to create a bigger more diverse food chain and more biodiversity in the caverns, its actually completely plausible if you have enough microbes eroding enough inorganic into organic stuffs.. nether caps would be some were in the middle or lower middle of that ecosystem. You'd need some kind of massive underground algea, or plankton system.. (herp derp the cavern pools should be full of the muck). (in real life there usually not as murky)... so some kind of algea that doesn't need the sun, is were your looking for your autotrophic whatever...