Good soil under rocks

I finally moved into my new home, and am ready to start gardening.

Yesterday I found the most fertile part of my yard - underneath a tree that I think might be a pecan tree. I will have to find out what it is. The most interesting thing about that area being the most fertile is that it is covered in decorative rocks. I assume leaves have fallen and made it under the rocks over the years, adding a good amount of organic material to the location.

Why do I think it is the most fertile? I was pulling up the volunteer clover plants and realized many had small intact roots. In other places in yard where I have pulled up clover, the roots don't always come up.

Maybe this does not mean the ground is fertile. But it does mean that the ground is good and airy. I will make a special effort to save the leaves that fall from this tree next year.

The next best soil I found in my yard was under a fence dividing my driveway from the neighbors. This narrow strip is also covered by rocks. I gathered quite a few earthworms as I pulled up clover plants from this area.

I think both areas were built up from decomposing leaves and other materials trapped by the rocks and fence. I might plant something in these areas.