Now we have not best season for mushrooms or for walking in the forest. Ground is still covered with snow, and I'm passsionately waiting that day when it will be possible to ride to the forest on a bicycle in search of snowdrops:-)
My answer to your question: moss grows best from that side of the tree where it has less sunrays and more moisture. It seems quite logical that it should be on the northern side. In addition, at school we were taught that the moss on the tree always points to the north, and this is a great way to navigate in the forest without a compass.
But in real life I had to see it on different sides of the tree. Sometimes I came across trees covered with moss from all sides, and it made me doubt the truthfulness of the school textbook. Maybe you can give explanation for this?
Btw, the log is just huge, I suppose that tree was no less than 50 years old. It's strange that they left so big and straight log to lay in the forest.
Your spring will happen eventually. Of course, that's easy for me to say, without being in the winter! You will appreciate your snowdrops, for sure!
I counted the growth rings of the tree -- and it's well more than 100 years just to where the little mushroom was growing! The rings are so close together because it grew in a mature forest. That is an old-growth forest and tree, for sure. The rings are so much farther apart these days, in the timber harvests from replanted forests.
I'll let you know about the moss! Thanks for venturing an answer!