The features of the physical setting create dry, thin, and infertile soils. Slopes are steep and convex, so water runs off quickly and soil doesn’t accumulate. Ecobit: Soil Processes: Creating a Place to Take Root

The underlying bedrock does not contain many minerals that promote plant growth. And the fact that the slopes face south to southwest means that there’s plenty of direct sunlight to evaporate moisture in the soil. Ecobit: How Topography Creates Microclimates

Because the soil is thin, the bedrock is near the surface and you’ll see rock outcrops as well as loose boulders.