There are places where tropical jungle forms a thick canopy that shelters plants growing in lower part of the canopy. The layers of canopy helps keep the humidity, thus forming a microclimate.

A good example is the moringa forest someone grew in their Phoenix, AZ front yard -- a city built in the lower Sonoran desert. Moringas are heat-seeking, drought-tolerant, fast-growing, and that guy's front-yard developed a canopy under which he grew more sun-sensitive plants. (Stuff labeled "full sun" does not mean "full Arizona sun).

The _simplest_ method for reversing desertification is to work with the natural tendencies so it does most of the work for you. That is, you jump start ecological succession away from desertification. You don't start with trees. You start by changing how rainwater is captured. In arid and semi-arid wastelands, although there isn't much rainwater, when it does come, it sheets off the ground. Rainwater harvesting structures as simple as swales (on-contour trenches), or even wide, shallow circles, capture just enough water for ecological succession to kick off. Planting things comes after, and helps accelerate ecological succession.

I lived here. Old man made this place long ago, never really raising rates like everyone else as things exploded. Reasonably priced, utilities included, well maintained. It’s a forest in Phoenix with many secret gardens , water fountains, items of interest. Yes a forest in Phoenix. It was a great place. https://www.rent.com/arizona/phoenix-apartments/forest-park-...