Trees

Willow-leaf oak is closely related to emory oak, but in some areas they appear to intergrade. Its leaves are generally shinier, slimmer, longer, and brighter green. Branch tips are generally less robust than emory oak. There is overlap in range of the two species in Sonora, but generally as one heads south Q. emoryi fades out as Q. viminea becomes more common. in areas of overlap they can grow at different elevations with emory oak at the lower end of the oak zone, often with or just above blue oak.

This large Acasia grows primarily along xeroriparian washes subtropical Sonora and southern Sonoran Desert. Its appearance is very similar to Acacia greggii, but often grows much larger with finer foliage and branch tips, more leaflets per leaf, and a gland on the petiole which is usually between the base of the leaf and the first 2 pinnae, where as in greggii this gland is almost always between the first 2 pinnae.

In our Sky Island region corkbark fir is know only from Mt. Graham and the Santa Catalina mountains, its southernmost range extent. In this region Abies lasiocarpa is threatened and is susceptible to effects from Climate Change as its habitat may move higher in elevation giving the species nowhere to go. Bark beetles, drought, and unnatural fire regimes also threaten the long-term existence of this species in the Sky Islands.

The white fir is the most widespread true fir in the Sky Islands. There are only 3 recorded localities in Sonora, 2 being from the first half of the 1900's. Known in the Sierra de los Ajos and suspected present, but not seen in recent years, in the Sierra El Tigre and Sierra San Jose.