Adam Clarke on Psalms 148:9

Mountains, and all hills - Whether primitive, secondary, or alluvial; of ancient or recent formation, with all their contents, quarries, mines, and minerals. But what a profusion of wisdom and skill is lavished on these! To instance only in the different metals, earths, and minerals; especially the precious stones.

Fruitful trees - עץ פרי ets peri, fruit trees of all kinds.

And all cedars - Every kind of forest tree. The formation of the fruits, their infinitely varied hues and savours, proclaim the unsearchable wisdom and goodness of God: not less so, the growth, structure, and various qualities and uses of the forest trees.