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Buried wood and frost heaves

 
Tyler Miller
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Location: Trapper Creek, AK (3a)
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I'm looking to build some raised beds early this summer. Not full-on hugelkultur mounds (although I am also going to try to build those) but more traditional raised beds.

There are lot of rotten logs on our property, and in most places we can't dig very deep before hitting a bunch of rocks. I was thinking of using some of the rotten wood to help fill up the raised beds in addition to digging up soil from other places to fill them.

This is a cold area, and sometimes when people bury things (like in garbage pits) the stuff eventually ends up being pushed back to the surface.

While it is cold, there is no permafrost. Most years there is also good snow cover.

I'm thinking that since the wood will be wet and heavy it will probably stay relatively put, especially if it is below the natural soil line.

What do you folks think?
 
gava gaia
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Hi Tyler,

My understanding (from decades ago, so there may be a better understanding out there) is that rocks get pushed to the surface at least in part by the finer grains of soil flowing under the rocks and pushing the rocks up. You can see this effect in a jar of uneven-sized objects. If you shake the jar, the *larger* items move to the top.

In the case of partly rotten logs, I would think their crumbliness (rather than their weight and wetness) would protect them from this effect somewhat -- but I would also think the crumblier the better, so as not to act like a solid object (rock).
 
Roberto pokachinni
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I think that since the wood itself becomes a sponge that absorbs water, when the log freezes, the ice will expand, and thus break up the log. Here's one way to look at it: Rather than pushing it upwards, the ice will push outwards in all directions; There is more opposing pressure (resistance to this expansion) from the soil below it, and so in taking the path of least resistance the ice will 'heave' more upwards than downwards. I think that frost will help your hugul or buried wood beds to aerate. If you have an excess of water beneath a stone, or log, this can cause 'ice jacking', as well. But I don't think that you will find this to be an issue, especially as your beds mature, and the wood breaks down.
 
Tyler Miller
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Thanks for the replies!

It sounds like it probably won't be a problem. That makes sense since quite a few people in cold places have built hugelkulture mounds and haven't had it happen to them.
 
Mick Fisch
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In your area I would bury mostly birch, if you start burying fresh stuff. The birch is open pored, so the water just wicks into it like a sponge. I've noticed it breaks down a lot quicker than the spruce, alder or cottonwood.

I lived in Talkeetna and went to high school there and finished up my last semester in Susitna Valley HS back in the 70's.

The trapper creek/talkeetna area and anchor point/ homer are the two best spots in the whole state!
 
Tyler Miller
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That's cool, you might have gone to school with some of my relatives.

I like the area quite a bit, but I'm biased since I grew up here and it's where most of my family lives. I just moved back after ten years in Fairbanks.
 
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