Forest signs

As I wasn't in the German Cubs or Boy Scouts I have little idea what the various signs one encounters in a modern forest mean. I know some denote trees infected by beetles that need to be removed and others just which trees to leave standing rather than harvest, the routes the harvesting machines should use .... etc.

I think for some reason a spot has been selected for research/testing purposes. Either for environmental purposes or maybe to access the damage done by deer nibbling young trees.

In the bottom photo, there is a short wooden post with a neon top that has been hammered into the ground, 3 metres to the right of the tree.