A Preliminary List of Bryophytes from the Organ Mountains, New Mexico

Abstract

Eighty-seven species and two varieties of mosses, and eight species and one variety of liverworts are listed from the Organ Mountains. The major vegetational zones for the mountains are characterized, and the list of bryophytes annotated accordingly. Sixteen mosses are reported as new to the state. Seventeen additional species and varieties are added to the state checklist from literature reports. The Organ Mountains are located in south-central New Mexico, Dona Ana County, about 16 km east of Las Cruces. They are formed from an elongate fault block uplifted highest on the eastern side. The center is a Tertiary quartz monzonite batholith that has been eroded into an amazing series of spires and pinnacles. The lower elevations have Paleozoic sedimentary rocks overlain by Tertiary volcanic deposits (Ungnade 1972). The Organ Mountains, reaching 2747 m in elevation, rise about 1.6 km from the Chi- huahuan Desert valley floor, where the dominant vegetation is Larrea tridentata (creosote bush), Yucca elata (soap-tree yucca), Prosopis glandulosa (mesquite), Gutierrezia sar- othrae (snakeweed), and Flourensia cernua (tarbush). The average annual rainfall for the Chihuahuan Desert near the Organ Mountains is about 330 mm (private record from the San Augustine Ranch, elev. 1372 m). The vegetation of the Organ Mountains is complex for so compact a mountain range. Rainfall patterns vary greatly between the eastern and western sides, further complicating the task of associating bryophytes with vascular plants. In addition, some plants such as Fallugia paradoxa (apache plume), Fraxinus velutina (velvet ash) and Pinus ponderosa (ponderosa pine) are common in the mountains, but occur throughout so much of the area that they are of little use as indicators of habitat. Dick-Peddie and Moir (1970) studied the vegetation of this range using various statis- tical methods. They found a complex pattern of vegetation associations that varied with to- pographical features such as slope exposure and steepness, elevation, and occurrence of large boulders and rock slabs. These factors cause great differences in the availability of moisture. The above authors divided the Organ Mountains into four consecutive and overlapping zones (from lowest to highest elevation): Upper Desert Grassland, Savanna and Woodland, Chaparral, and Deciduous Woodland. Roughly one-half the height of the Organ Mountains consists of open soil-laden slopes containing the three lower zones. Plants characteristic of Upper Desert Grassland are: Mimosa biuncifera (mimosa), Happlopappus laricifolius (larchleaf goldenweed), Parthe- nium incanum (mariola), Dasylirion wheeleri (sotol), Celtis reticulata (netleaf hackberry), 007-2745/82/307-311$0.65/0