In the Chihuahuan Desert of New Mexico, Trans Pecos Texas and Northern Mexico, we have many mountain ranges that have an ecotone at the base which I call the Desert Edge Woodland. It's very arid, dominated by Quercus species and averages between 12 and 15 inches of annual precipitation, rarely higher. 50% of precipitation falls during the summer monsoon season which is not much when you consider that the daily evaporation rate can exceed 1/2". Despite the aridity the oaks in this ecotone can still reach 40 feet tall or larger and you might assume that when grown for landscaping that these same species could tolerate the same 12 to 15 inches of annual moisture, however they cannot. Under cultivation the Chihuahuan Desert Native Oak will most likely need about 20 to 30 inches of annual moisture supplemented if planted in Albuquerque, Tucson, El Paso or Las Cruces. Nothing close to the 12 to 15 inches of its native counterparts. The reason for the lack of the same hardiness and low water tolerance of the cultivated plant versus the wild plant is that the cultivated plant lacks the full ecology of the terrestrial biosphere including a pipeline of Supramolecular Humic Acids and a Mycorrhizal relationship.
