CREOSOTE BUSH: LONG-LIVED CLONES IN THE MOJAVE DESERT

Frank C. Vasek
1980 American Journal of Botany  
JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org. ABSTRACT Creosote bush clones in the Mojave Desert develop by irregular radial growth, stem segmentation and the production of new stems at the outer edge of
more » ... he outer edge of stem segments. The resulting circular clone encloses a central bare area as the central dead wood rots away. Old clones become elliptical and may exceed 20 m in length. Modern growth rates estimated from annual increments in stem wood of seedlings (0.73 mm/yr) and young clones (0.82 mm/yr) approximate those estimated for radiocarbon-dated wood samples (0.66 mm/yr). Assuming comparable growth rates through time, the extrapolated age of the largest known clone (average radius = 7.8 m) may approach 11,700 years. If growth rates have changed, that clone's age may be somewhat less. CREOSOTE BUSH, Larrea tridentata (Sesse and Moc. ex DC) Cov., is a common, widespread, and often dominant plant over desert areas of the southwestern United States and northern Mexico. Numerous studies have been made into creosote bush ecology, distribution, reproduction, development, phenology, community structure, use by animals, etc. (see Mabry, Hunziker, and Difco, 1977 for summary). Despite an extensive literature on creosote bush, its age and longevity have received scant attention. Large shrubs near Tucson, Arizona, were estimated at ages "well in excess of 100 years" on the basis that little change in size or bulk occurred during the course of a 30-year photographic record (Shreve and Hinckley, 1937). A population in southern Arizona, expanding after historically recent invasion, included plants approaching 65 years of age as estimated from counts of growth increments in stems (Chew and Chew, 1965). Large clumps of several separate bushes or crowns were observed by Barbour (1969) who suggested that bushes may be aggregated as a result of asexual reproduction. The development of clones was briefly described (Vasek, Johnson, and Eslinger, 1975; Vasek and Barbour, 1977) as a process in which radial growth, the repeated production of new branches at the periphery of a crown, the death of old branches at the center of a crown, and eventual segmentation of a crown led to circular clumps of satellite bushes with dead stems or, eventually, I
doi:10.1002/j.1537-2197.1980.tb07648.x fatcat:4lbn2okz2jb2vda7doahyz44di