The dogwood pumps the calcium up to its leaves. When the leaves fall away and are blown under other trees they rot and provide calcium for that tree. I admit when nature prunes she's a bit messy for the average home owner's taste. Visit a forest that has been taking care of by itself for ten years or so. It may not be neat, but the ground is alive.
Wildlife finds food and habitat and make their contribution to the cycles of life.
Its all there. You can touch it. You can smell it. You can see it. You can hear it.