Forcing shapes in live trees is not unheard of and I'm wondering if the timber has been deliberately shaped in order to help serve a specific construction purpose.
I can't find anything about the industrial history of the area, but the site is very close to the Oder, and the lower curve of the trees shape - in some cases, at least - is quite reminiscent of the shape of a boat's tumblehome; but you'd only get half a rib out of each - so I don't think so.
Another shape that comes to mind is the onion dome style of church architecture - but, although the Poles build some beautiful wooden churches, the onion dome is, I'm pretty sure, mostly a Russian thing.
But maybe you can see what I mean about the shape:
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Mind, I don't think it's either. But, unless it's simply the whimsy of some old landowner, created to impress his boar hunting friends, I'd bet a bag of toffees it's to do with making something specific.