In our region Madrean Oak Woodland dominates vast swaths of what many know as the "middle" elevations. It comes into full force in elevations above semi-desert grasslands or oak savannah, or above thorn-scrub and occasionally tropical deciduous forest in the southern latitudes. It covers most of the Sierra Madre below the pine/oak zone and significant areas of all Madrean Sky Islands.
Madrean Oak Woodland's existence appears to be closely tied to the monsoons. And indeed the community is glorious and especially loaded with life once the monsoon season is in full force. These woodlands host a high diversity of plant and animal species. In Arizona and New Mexico the community is usually dominated by 1-3 species, but as one goes south the dominant species shift and total numbers of species increase.