Otay Manzanita [Arctostaphylos otayensis Wies. & Schreib.]

Otay Manzanita [Arctostaphylos otayensis Wies. & Schreib.]

Listing CNPS List 1B R-E-D Code 3-2-3

State/Federal. Status -- /C2 ERICACEAE Jan.-Mar.

Global Rank G2 State Rank S2.1

Distribution: San Diego County

Habitat: Otay Manzanita grows in chaparral on metavolcanic peaks. On San Miguel and Otay Mountain the soil is mapped as San Miguel-Exchequer rocky silt loam. Typically, the xeric chaparral is a dense tangle of shrubs with a height of perhaps five to six feet. Arctostaphylos glandulosa ssp. zacaensis and Ceanothus tomentosus ssp. olivaceus may grow nearby; Adenostoma fasciculatum is usually the dominant shrub and soils may be quite shallow with much exposed rock flake.

Known Sites: Scattered populations for this shrub occur on San Miguel Mountain and in the Jamul Mountains; excellent stands occur in chaparral at upper elevations of Otay Mountain including west of Hubbard Spring near Woodwardia Canyon. An old herbarium collection on gabbroic soil at Guatay Peak is misidentified according to Wells; a Data Base report from southwest of Julian is also presumed to be erroneous.

A Baja California population close to Arctostaphlyos otayensis was located in 1994 by C. Reiser and D. Hannon approximately nine miles north of Guadalupe Valley and La Mision, along the dirt road to La Zorra. It grows with chamise and Lotus crassifolius var. otayensis upslope from a sizeable vernal pool which is situated adjacent to the road. This sparsely hairy shrub superficially resembled the Otay Manzanita with no basal burl, a relatively small, non-sticky fruit, and long floral bracts; however, it had brighter green and glossier leaves and did not have glandular hairs. Several peaks immediately south of Otay Mountain in Mexico have the potential to harbor this southern San Diego County endemic.

Status: Populations of Otay Manzanita are presently stable. It is potentially endangered from residential development in Proctor Valley on the flanks of San Miguel Mountain, and from blocks of proposed ranch-style housing south of Dulzura in the foothills near Otay Mountain. All populations are recommended for protection.

Rainbow Manzanita [Arctostaphylos rainbowensis ] J. Keeley & Massihi

Listing CNPS List 1B R-E-D Code 3-3-3

State/Federal. Status -- None ERICACEAE Jan.-Feb.

Global Rank G2T2 State Rank S2?

Distribution: San Diego County, Riverside County

Habitat: Southern Mixed Chaparral is the preferred habitat with a relatively dense canopy from six to eight feet being common. Rocky Cieneba and Las Posas soils are found in areas of heavy concentrations of Rainbow Manzanita where it occurs north of Pala. Adenostoma fasciculatum is usually a major constituent of chaparral where this species grows; Xylococcus bicolor may be well represented nearby.

Known Sites: This shrub is the dominant manzanita on the Pala/Temecula Road. During a 1990 survey, more than 5000 shrubs were estimated to be present in the hills flanking Pala Creek. Rainbow Manzanita is common on Magee Road near the Riverside County border and extends eastward into the Agua Tibia Wilderness. These are the only areas where it can be considered abundant. It is scattered throughout the rugged terrain from Pala westward to the Santa Margarita Mountain's eastern slopes. This shrub is uncommon north of Fallbrook in chaparral along Sandia Creek, and southward near the intersection with De Luz Road where a sizeable population was found on a bench overlooking the Santa Margarita River. It is uncommon on Camp Pendleton in heavy chaparral near upper Roblar Creek. In Riverside County it is rare in the Santa Rosa Plateau region such as in Walker Basin, near Calle Jardín, and in chaparral adjacent to La Ventana Road; also to the north near Mountain Avenue west of Alberhill. A handful of shrubs were seen on a chaparral slope of the Merriam Mountains, west of Interstate 15 and Windsong Lane; this is south of all other reported sites. Old biological survey reports note sites northwest of the Garnsey Ranch and north of the Tenaja Truck Trail, at several locales on Monserate Mountain, near Rainbow Glen Road west of Rainbow Creek, west of Trujillo Creek and southwest of Magee Truck Trail, east of Keys Creek and west of Mountain View Lane northwest of Valley Center, near Sudale Ranch Road north of Fallbrook, near Gomez Creek and Rainbow Crest Road south of Rainbow, west of Rainbow Heights Road due east of Rainbow, north of Chief Mountain in the vicinity of Magee Creek, and 0.5 mile west of Daily Road on the San Diego side of the San Diego/Riverside County line; as well as east of Slaughterhouse Canyon near the Santa Rosa Plateau in western Riverside County.

Status: Rainbow Manzanita's populations are presently stable. It is threatened by continued orchard expansion into the Pala and De Luz regions. All larger stands of this shrub should be protected. Taxonomic similarities exist with Arctostaphylos peninsularis ssp. peninsularis from Baja California.

Copyright © May 1994 Craig H. Reiser.

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