So I was wondering – if organic material in my backyard compost pile generate heat and steam, why aren’t forests floors around the world doing the same?
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The compost pile is a concentrated large pile of material which maintains the heat due to the volume of the pile compare to the surface area.
“Composting” in a forest really only happens in the top inch or so of soil, so any heat that’s produced dissipates very fast.
Bacterial growth generates heat. Because compost is not distributed evenly into the ground, but in a concentrated heap, that heat doesn’t dissipate: that is, it is more difficult for the inside of the heap to cool down.
That is why “professional” composting has the concern of “shuffling” the heap from time to time, to cool the heap: you want bacteria to grow, and temperature is important for that. But if it reaches 65C the bacteria may die and not “finish the job”, making composting to end up slower.
In a forest floor, because the content is distributed evenly on the ground, there is not a big “inside” protected from the cold.
[https://compost.css.cornell.edu/physics.html](https://compost.css.cornell.edu/physics.html)
Great answers here. So the forest decomposition is doing the same thing, just on a much larger scale… another example you can consider is why hay bales sometimes get too hot and burn. Too much decomposition going on in a tightly packed bale. Round bales are less likely to do this due to air flow compared to square bales.
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Scrub/bush turkeys in Australia create compost heaps (several feet/over a metre in diameter and just as high) to create heat to incubate their eggs. So technically it *does* happen, just in very, very specific circumstances.
Great explanations and comments everyone. It all makes sense.
The organic material on the forest floor accumulates rather slowly, or rather in chunks, over the course of time, and ultimately in rather thin layers. It is simply not concentrated enough to get the bacteria growth and heat necessary to steam the same way a constructed pile of compost will.
I was under the belief that in forests underneath the fallen debris is a layer of mycelium or fungus type mushroom layer that eats the fallen organic matter
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