Why can't my carpenter's workshop find any wood?

I chopped down some trees a while ago and set up a wood stockpile outside my fortress. The stockpile was filled up as expected. I then build a carpentry workshop on z-level below and assigned it to make 3 wheelbarrows. The tasks where canceled because it could not find any logs. But I clearly have logs - both outside on the ground and in the stockpile. So why won't it make the wheelbarrow? The same is true with barrels.

Moreover, I made a need wood stockpile right next to it and the dwarfs are not moving anything into it. The wood is not forbidden or dumped, I don't think I have any links set up, I didn't build any barrows, and my dwarfs have standing orders to gather wood. I uploaded my save here.

Is there something I'm missing?