They're talking about species diversity of vegetative communities. SCL has slower drainage than SL, and there is an edge effect too, likely boosting diversity
Everything here is clay. We have like 1/4 inch of rich top soil. Then directly below that, red clay. Sucks in the summer because it bakes and turns to bricks because we're so hot and dry. Suck in the winter because it cannot hold water, so the yard turns into a pond any time we get more than a sprinkle. Don't get me started on pH.
Hidden in your post was sandy loam, who is she?? How is she related to Sandy C. Loam???? Who’s really pulling the strings here?????????? WHO SMUDGED THE DIRT DOCS??????????????????