Acer palmatum

The tree has the second flush of foliage after defoliation. Now mushrooms grow from the substrate. Good or bad? 

I think it is ok. Probably sign of good conditions in the soil. 

On the second and third picture, there are new roots peaking from moss. Large root was removed at that location in spring. This is a good sign. Possibly one of the reasons for the popularity of this species in Japan and elsewhere. Healing of the wounds like no other species, roots grow like crazy, nice foliage with changing colours, tender ramification. The winner among deciduous. 

Back to moss. Using moss all year round gives your tree 1/3 more space to grow roots. In modern substrate without moss, you can hardly see any roots in the top section since it is too dry mostly. Don't be afraid of moss. Methinks.

Prunus spinosa

“You can change what you do, but you can’t change what you want.”  Tommy Shelby