This is a great question. It is great to look for deeper meaning in all stories, even short stories like "The Interlopers."
The broken tree in the story that pins down both Georg and Ulrich is important to consider. A little background will help. Georg and Ulrich in the story are archenemies. They hate each other, and their feud has lasted for a few generations. Both feel that the tract of land they are on belongs to them. The land, therefore, is the bone of contention.
This conflict begs a question. Can a man really own land? To put it another way, can a man own nature? Who decides?
By having a storm in the short story, we realize that nature has a mind of its own. By having that storm knock down a tree shows that men own nothing, not even their lives. Nature is the one who is in control. So, their foolishness is underlined. The broken tree, therefore, symbolizes the power of nature. Could it be that nature is saying that the men are the interlopers?