Some links on atmospheric pressure and altitude effects on plants. I found some of this interesting as a mountain grower with constantly increasing temperature. The changes in pressure was surprising to me, but then I thought about weather patterns changes and it kind of made sense.
https://sbir.nasa.gov/SBIR/abstracts/87/sbir/phase1/SBIR-87-1-12.06-3053.html
https://www.ncbi.nlm.nih.gov/m/pubmed/11538810/
https://nph.onlinelibrary.wiley.com/doi/full/10.1111/nph.14332
Good for a read anyway 
Posting my 2c from 7,000+ feet:
I can at least say that several thousand feet less PSI affects at minimum hash type.
My first ever ISO oil, made 17 years ago, wasn’t purged so much as left to sit near an open window with a screen. I have never had to purge any types of oil at 7k, and all my oils solidify and crystallize like… Well, if you’re familiar with organic chem: My “oil” ends up striating into needle-like shards, much like an hcl salt.
Simply put: With pure enough solvent and no vacuum filter, going up a mountain should give you a good purge just evaping