Restoration in hyper-arid environments?

 Is is possible to plant trees and restore grassland savanna in a hyper-arid desert?  

In Al Baydha it sometimes doesn't rain for 26 months, and apparently there are trees that can survive and thrive in that environment.

The Story of Al Baydha: A Regenerative Agriculture in the Saudi Desert.

Bear's Ears Research on Legacy Human Plant Communities

The research is quite interesting. They have determined that a large suite of plants used by people in the past are more likely to be found in the vicinity of archaeological sites on Bear’s Ears NM. Basically people were planting medicinal and other useful plants, and those plant communities have persisted at these locations in greater numbers to modern times. We see similar things here in Arizona with agaves, yucca, devil’s claw, and a few other plants. In AZ the phenomenon is sometimes referred to as “Legacies on the Landscape.”

https://www.pnas.org/content/118/21/e2025047118

But looking through the Supplemental table for the paper, they basically included every species that grows up there.  Not surprisingly, native peoples utilized most of the naturally-occurring botanical resources on the landscape.   So their results are really more that cultural sites are associated with biodiversity in general, not specific assemblages of “cultural” species.  

Also, the paper implies that the causality goes native people>plant diversity, but it could just as easily go plant diversity>native peoples, since native people would be more likely to settle in places with more plant diversity (e.g. places with water).

I would be more interested in a paired-down list of the plant species that are truly cultivated and remain associated with prehistoric sites.  For AZ, agave, yucca, devil’s claw, and a few other plants.  Definitely Wolfberry (Lycium pallidum).  They list Wild Potato, Solanum jamesii, which is interesting and does occur in AZ above the rim…..they also list Chenopodium sp, which is a common weed so I’m not convinced that is a good marker of anything.

Chenopodium are usually ubiquitous in pollen and macrobotanical samples taken from archaeological contexts. The typical interpretation is that these plants were used way more than we think. Hard to know whether weedy plants were being intentionally planted or if they started growing more in areas where people were eating, processing, and depositing seeds through their waste. There are a few Chenopodium species that were domesticated prehistorically. In the western US these are amaranths, goosefoot in the eastern US, quinoa in South America, etc.