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I would like to explore how to design an alien planet featuring plants and animals but with a much more prominent ecological role for fungi. More fungi, larger fungi, more complex and beautiful fungi.

Fungi are heterotrophs so they still need plant (and animal) matter to feed on.

What type of world would suit them best, while still allowing reasonably bio-diversity and non-fungi sapient animals to develop a civilisation (maybe living in cities comprised of cultivated giant fungi)?

Some ideas I had:

  1. A long day/night cycle gives fungi advantages over autotrophs - at least during the night.
  2. Plant or animal life which blooms and expands quickly then dies off equally quickly yields a rich source of food for the fungus species.
  3. A red dwarf type sun would alter the balance of power between fungi and plants by making photosynthesis less efficient.
  4. Fungi are noted for species which are radiation resistant - how can I use this?
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Visible mushrooms* are significantly more prevalent in forest than in meadows. Why is that? Because those species of fungi can break down cellulose while very few animals can. They are filling an important niche in the ecosystem. I think you've already identified a few good advantages you can give to fungi. Maybe your world should also be wet and temperate, favoring large trees and forests. Then your fungi have a prevalent food source.

Maybe lower gravity is a good idea because mushrooms tend to break fairly easy. Lower gravity means taller trees and taller mushrooms! I don't see it being to the mushrooms advantage to be taller than trees. They shouldn't be crowding out there food source.

*I mention mushrooms, because I just learned that fungi include yeasts and molds and those are literally everywhere.

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Planet Mushroom is a large planet locked into a tight orbit around a red dwarf. It's not tidally locked, but the casual observer might think it is, due to its 37-year long day. A thick, hazy atmosphere and strong winds distribute temperatures fairly evenly around the globe, stopping the day side from burning and the night side from freezing, but few plants are capable of surviving the long night.

The result of this phenomenon is that, every evening, all of the plants in the biosphere flower, produce seeds, and then, just as night falls, all die. Simultaneously, the spores of countless species of fungi that have lain dormant beneath the earth during the 18-year long day awaken, and start to grow.

During the night, these fungi have no competition, but slowly run out of decomposable organic matter to draw energy from. The fastest growing, least efficient fungi grow first, release spores, and then serve as nutrients for a succession of progressively hardier fungi, leaving only the sturdiest such organisms standing when day comes.

Day, of course, brings light, and with it a new growth of plants. Fueled by a rich soil, courtesy of the long night of decomposition, growth is rapid, and within a few years time a mighty forest stands anew, ready to continue the cycle.

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  • $\begingroup$ Nice, but I need some species of fungi to persist for multiple 'days; I would like the longevity of some species to match that of trees $\endgroup$ – rumguff Aug 31 '15 at 22:30
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    $\begingroup$ Entirely possible. Some of the fungi may be able to survive the gradual nutrient depletion of the night and survive into the next day, allowing them to survive for days on end. It's unlikely that the entire such organism would be made of living tissue, but more likely that a single huge trunk of unliving matter would be enveloped by a thin mycelial skin, connected to a larger such network underground. Such an organism could even by a lichen-like symbiont, in which the plant grows on the trunk during the day, then dies back and is replaced by the fungus, which protects at night. $\endgroup$ – ckersch Aug 31 '15 at 22:38
  • $\begingroup$ Cheers - it seems I have a lot of research to do about mushrooms... $\endgroup$ – rumguff Sep 1 '15 at 18:54
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One issue with your post is that fungus depend of processing organic material to get their energy, so you cannot get lots of fungi without having lots of (at least) plants or algae to feed upon.

In the end it is quite simple:

  • the star sends energy to the planet.

  • plants and algae and similar (fitoplacton) catch some of that energy. Some of that energy is stored as organic compounds, some is used for the vital processes of plants and algae.

  • All the other levels feed off the energy stored in the plants and algae and similar. As they are not 100% efficient, each additional level has access to less energy.

So, anything that limits autotrophs growth will equally limit your fungi. You actually need the opposite, a very efficient photosyntesis that allows a given surface of autotrophs make available lots and lots of energy for your fungi to consume. And, of course, not animals at all. Apart from that, your autotrophs will need some means of defending from fungi.

An option could be trees that, once its bark becomes too old or fungi-ladden, just allow it to fall apart (as decidious trees do with the leaves) to grow a new, healthy one.

Intrepidhero's suggestion of low gravity is a good one, too.

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  • $\begingroup$ I get the need for autotrophs to form the basis of the food tree, but can I do without large trees, such that the plants are mainly aquatic or airborne plankton so some such? $\endgroup$ – rumguff Aug 31 '15 at 22:33

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