Cold Climate Adjustments?

I'm in Zone 3A, long cold winters. When I make my hugel beds do I still want to use large logs, Frisbee size circumference and larger? Or do I want to use smaller logs, maybe 3/4 that size? I figure with the long cold winters it will take significantly longer for the wood to break down and decompose. What might take 3 years in a warmer climate might take 6 in my area. Is my thinking right or am I off track here ...

It depends less on how cold your minimum is in winter (which is what USDA Hardiness is about) and more on your spring, summer, and fall. Most zone 3 places do have short, cool, summers, but not all. What's your summer like?

I don't think it matters much, the log size. It's true that larger logs will take longer to break down, but that's not necessarily a bad thing in itself

Isn't the decay of the logs going to create some heat, I mean they are basically composting. And during the winter all that heat will be insulated by both the soil layer and the snow.

Although, even at the soil surface, things seem to break down just fine under snow cover, leaves and twigs and pine cones/needles I mean.

Also, freeze/thaw cycles have a way of breaking things down, so if your hugel does freeze solid a few times a year that might actually make it break down faster than if it didn't freeze at all.

Sepp Holzer invented hugelkultur (as far as I'm aware) and he lives in the mountains in northern Europe.

For all of these reasons I think hugelkultur will work fine anywhere there are trees to be buried. If you go far enough north/high enough in elevation, the trees start getting smaller anyways. As long as you aren't importing logs from somewhere else I think you're good.

In hugelkultur (invented back in the 1600's in Germany) the logs are being decomposed by fungi (no heating occurs with fungal decomposition).
The purpose of hugel beds is the collection and retention of water for plant's roots to take up during times of draught.
The freeze thaw cycles do to a hugel the same thing it does to all ground, it heaves up as the water freezes and it then collapses as the ice thaws.
What that means is that the winter heaving helps to settle in the hugel and that means it shrinks down in size.
The first hugels (theory #1) were created (probabaly by accident) when leftover wood was stacked and then the wood became covered by leaves in the fall and when spring came those leaves settled in between the stacked wood pieces, over time the structure became a mound that would support plant life.
Theory #2 (most likely) goes with the  idea that farmers, needing some easy and rapid to build wind breaks stacked up wood high enough to keep the wind from damaging their crops and they went so far with the construction as to shovel dirt on to cover the logs so they wouldn't rot away very quickly.
At some point the seeds lying dormant in the soil that was piled on the logs sprouted and the farmers realized they could grow vegetables on their constructions.

Hugelkulture does not work in extremes of weather areas, such as rain forest and deserts, the design works best in temperate zones.

Redhawk

When I said freeze/thaw cycles break things down I meant more on a micro level, with the expanding water causing the cell walls/membrane to burst, sort of like why you don't want to freeze, thaw and refreeze meat or vegetables.  I don't think dead wood is immune to this once it has soaked up extra water.

I appreciate the replies, thanks!

My thinking was that a partially decomposed log would have a much greater ability to absorb water then a solid newly felled tree. I thought if the long winters were keeping the logs from decomposing they would not be as effective in retaining water.

Glad to know it won't be an issue, thanks again  :)