The most important example of foreshadowing in the story comes when Georg and Ulrich are trapped beneath a falling tree:
A fierce shriek of the storm had been answered by a splitting crash over their heads, and ere they could leap aside a mass of falling beech tree had thundered down on them.
This is a clear example of foreshadowing, as the two feuding old men have been attacked by the forces of nature, and this is exactly what will happen later on when, stricken beneath the beech tree, they are set upon by a pack of ravenous wolves.
What is particularly effective about the above excerpt is that it highlights how vulnerable Georg and Ulrich are to the forces of nature. For all their hype and bluster, and all their numerous threats against each other, when it comes down to it they're nothing in the overall scheme of things. Nature is king in this part of the world, whatever these two old bluffers might think. It was here long before either of the two men's families laid claim to this plot of land, and it'll still be there long after they've been torn to pieces by wolves.
Note also the reference to the "fierce shriek of the storm." This chillingly foreshadows how the trapped men will almost certainly respond when a pack of hungry wolves descends upon them and they suddenly realize that they're about to become their dinner.