>>2770937About half of the upland pine-oak forest area of Arizona are mature stands in the same configuration as they were after the younger dryas. The other half was disturbed by humans at some point in the last 150 years and regrown. The average stand height in certain geographically large areas near the Rim is 90-110 feet and the average stand age in these areas is older than 150 years among ponderosa, the white oaks (and other oaks), maples, aspens, sycamores etc in these forests fill in gaps in the canopy and are often younger than 150. In riparian areas the ratio of conifer to deciduous trees is often inverted, 70% deciduous 30% conifer and this decreases with distance from drainages or canyons, many pristine riparian areas hold old growth deciduous and mixed forests (some trees older than 400 years old among oaks and sycamores, average ages over 130 years old among mature specimens). The pre younger dryas forests of AZ and the southwest in general were predominantly lower and mid-elevation spruce-fir forests and everything above 1500m was in the sub-arctic taiga or aspen parkland regime, when things warmed up the lowland pine-oak forests migrated and became highland pine-oak forests.
