This cache is, indeed, in the hole in the middle of a tree, about
3m above the ground.
If you're very, very tall, you can just reach up and grab it, but
the rest of us will need a little bit of help.
The 500ml cache container has strong magnets on all sides of it,
so you should be able to 'fish' it out by using something made of
iron on a string attached to a stick.
(Polar bears love magnets, that's why they live at the North
Pole!)
If you forget to bring some string and metal (or are only
reading this for the first time with the GPSr saying "you're
here"), fret not!
There's an eclipse mint container with some helpful bits in it
hidden in the same tree! Just reach up into the hole on the other
side of the tree and it's just above the hole on the side nearest
you. Held on by a magnet, naturally!
Use it to retrieve and replace the cache, then put it back there
for the next cacher who needs it. You'll still need your own stick,
though.
(There's probably cans and bottles in there as well, you could
always do a CITO while you're here...)