Wow. Nice article. Makes me nostalgic for my days in Arizona...
Keeping western junipers here in the East is problematic. The climate is very different. Heat and humidity are the culprits, I suspect. The desert is not a swamp
as most of the eastern coast is. The heat is different here. In D.C. (a former swamp drained to construct the city), temps may only be in the mid 90's on a hot summer day, not really the hellish 110+ the desert can reach. However, the humidity can also be in the low 90 percents too. That doesn't allow for alot of respiration. Humans can't sweat effectively, neither can plants respire as effectively.
There are news stories every summer here noting that a tourist from out west goes jogging when "it's only 90," only to collapse from heat exhaustion 30 minutes out.
The higher humidity levels can lead to difficulties in growing bonsai if you're not attentive. High humidity means water stays in the rootball alot longer in bonsai because they're not respiring it through their leaves effectively. It's possible to drown a bonsai with overwatering in the summer, even if you're using a thoroughly draining soil mix.
Too much water, not enough respiration can stress trees out over time too, even if you are attentive to watering. The local trees sometimes enter a summer dormancy, where they just shut down active growth for a few weeks in the hottest part of the summer. That can also lead to more water accumulation in the rootball if you're not aware of what's happening. Watering has to be adjusted accordingly.
Sorry for the longwinded response.
Great article. Keep this kind of thing up.