title: Size class structure, growth rates, and orientation of the central Andean cushion Azorella compacta.
abstract: Azorella compacta (llareta; Apiaceae) forms dense, woody, cushions and characterizes the high elevation rocky slopes of the central Andean Altiplano. Field studies of an elevational gradient of A. compacta within Lauca National Park in northern Chile found a reverse J-shape distribution of size classes of individuals with abundant small plants at all elevations. A new elevational limit for A. compacta was established at 5,250 m. A series of cushions marked 14 years earlier showed either slight shrinkage or small degrees of growth up to 2.2 cm yr(-1). Despite their irregularity in growth, cushions of A. compacta show a strong orientation, centered on a north-facing aspect and angle of about 20° from horizontal. This exposure to maximize solar irradiance closely matches previous observations of a population favoring north-facing slopes at a similar angle. Populations of A. compacta appear to be stable, or even expanding, with young plants abundant.
authors: Department of Biology, Regis University , Denver, CO , USA.
authors: Catherine
authors: C
authors: Kleier
authors: Department of Mathematics, Regis University , Denver, CO , USA.
authors: Tim
authors: T
authors: Trenary
authors: Nexleaf Analytics , Los Angeles, CA , USA.
authors: Eric A
authors: EA
authors: Graham
authors: Department of Computer Information Systems, Metropolitan State University , Denver, CO , USA.
authors: William
authors: W
authors: Stenzel
authors: Department of Ecology and Evolutionary Biology, University of California , Los Angeles, CA , USA.
authors: Philip W
authors: PW
authors: Rundel
keywords: Andes; Cushion plant; Growth rate; Parque Nacional Lauca; Puna