You may not be doing it intentionally, but it's your presence that seems to inspire the roots to move. See here—

[And he'll go on to approach the next tree with a shell beneath it, reaching down to claim the blackened fragment, but the root does little to make his life easier, staying firm as Cyrus tries to carefully pull the shell out from beneath it without breaking it further.

He leaves it where it is, gesturing for Alfyn to try the same.]

It doesn't care to assist me, but I hypothesize that if you were to approach, it would feel inclined to oblige you.