soil rejuvenation/compost pile in open yard

I am wanting to use a spot in my yard thats on the edge of the property toss my used soil add things to it(compost,guano,bone meal,will probably be light, not wanting a "supersoil"). My biggest questions are in regards to below the soil and above. Should I put a tarp underneath all of this soil? im leaning towards yes. The area has a tree that sits over it(cannot remove it) that will drop crap in the soil. Should I put a tarp over all of the soil as well? Does the soil need sun? It is my intention to rejuvenate the soil used in my perpetual grows. Can you please comment on my particular situation?

I reuse my soil. I mix my ingredients and put them in a large trash can and keep that cover, however, my compost pile is exposed to the elements.