Rocky Mountain Research Station

Title: Geologic associations of Arizona willow in the White Mountains, Arizona

Author: Long, Jonathan W.; Medina, Alvin L.

Date: 2007

Source: In: Barlow-Irick, P.; Anderson, J.; McDonald, C., tech eds. Southwestern rare and endangered plants: Proceedings of the Fourth Conference; March 22-26, 2004; Las Cruces, New Mexico. Proceedings. RMRS-P-48CD. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station. p. 49-58

Station ID: P-RMRS-048

Description: The Arizona willow (Salix arizonica Dorn) is a rare species growing in isolated populations at the margins of the Colorado Plateau. Although its habitat in the White Mountains of Arizona has been mischaracterized as basaltic, the area is actually a complex mixture of felsic, basaltic and epiclastic formations. Comparing the distribution of the Arizona willow to mapped geologic formations revealed that occupied sites are strongly associated with felsic, coarse-textured Mount Baldy formations. The most robust subpopulations are located in three glaciated reaches, but about half occur in exposures of the Sheep Crossing Formation. Other sites occur in areas mapped as Quaternary basalt, but these lie either downstream from Mount Baldy formations or where basalt and porous cinders form a relatively thin mantle over the Mount Baldy formations. Glacial deposits, the Sheep Crossing Formation, and large alluvial deposits have high hydrologic conductivity that may favor the willow. Despite its affinity for the Mount Baldy formations, the Arizona willow is not a strict substrate specialist, since it has survived when transplanted into basaltic areas in Arizona and it grows in different substrates in New Mexico and Utah. Nonetheless, understanding the geologic associations of this rare plant can help to explain its distribution and to design appropriate conservation measures.

Keywords: plant conservation, Arizona willow, Salix arizonica Dorn, White Mountains, Arizona, Colorado Plateau

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Citation

Long, Jonathan W.; Medina, Alvin L.  2007.  Geologic associations of Arizona willow in the White Mountains, Arizona.   In: Barlow-Irick, P.; Anderson, J.; McDonald, C., tech eds. Southwestern rare and endangered plants: Proceedings of the Fourth Conference; March 22-26, 2004; Las Cruces, New Mexico. Proceedings. RMRS-P-48CD. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station. p. 49-58.