It goes further than that: air near the surface of the earth is doing a lot more interacting with the earth than the other air, and is getting and keeping a lot

It goes further than that: air near the surface of the earth is doing a lot more interacting with the earth than the other air, and is getting and keeping a lot more heat and dissolved gases. That includes air at sea-level or air at a mountaintop. Thus, there is no natural analogy to a tree growing atop a 500 foot building. Even bristlecones at 10000 feet still benefit from air that has been in prolonged proximity to a surface.