Dreese-Williams are keen on unusual materials, so when they learned that a load of Sitka spruce trunks were available they had the load sent south from Alaska. This tree naturally develops these curious, tumor like galls, so when planted in a circle of standing poles, they help transition from bare desert to the wall and entry gate. They were also used as posts for the patio roof. They'll survive far longer in the dry air climate of the desert compared to regions of higher rainfall.
This is a good lesson in large scale site design. Such large spaces with spectacular views require monolithic elements to remain in scale. However, the way humans experience these same elements in space must be at the human scale. When both requirements are met, then the landscape becomes wholly integrated so at every turn the views are harmonious.