I want to know if you use combination for a better developing of the trees and the soil. I'm from South America where ancient groups use to live and cultivate in the dessert by promoving the best combination of plants. The system is better know for the "three sisters" (pumpkin, bean and corn) but is used with a large number of different domestic plants (more than a hundred, without counting their varieties, potatoes have more than a thousand) and some wild ones. Trees for water and shadow, big leaves plants for moistness (mostly cucumbers), some plants for nitrogen fixation (mostly legumes), different varieties of herbs for soil development, and so on. Some garden have endure until our days, and they are beautiful, dark esmerald green in the middle of the dessert.