TILLANDSIA-LANDBECKII IN THE COASTAL ATACAMA DESERT OF NORTHERN CHILE

The crest of the Cordillera de la Costa inland from Iquique supports a unique Chilean loma communities or tillandsiales of an epiphytic brom eliads growing on sand. These communities, similar to tillandsiales of the loma formations of coastal Peru, contain only a single vascular p lant species, Tillandsia landbeckii. This terrestrial epiphyte obtains all of its moisture and nutrition from the absorption of fog moisture through specialized leaf scales, and furthermore utilizes CAM metabol ism as a physiological adaptation to its arid habitat. The distributio n of Tillandsia landbeckii is highly localized to steep, southwest-fac ing slopes at 930-1 050 m elevation. Here it grows in lens-shaped moun ds forming bands across the slopes. Mean canopy cover of these large m ounds was 24% over a broad study area, and reached to nearly 50% local ly at higher elevations. Mean community biomass was 715 kg ha-1 overal l, and reached 1 460 kg ha(-1) on upper slopes. The development of ind ividual tillandsia mounds represents a dynamic process of colonization , growth and development, and eventual senescence. The highly specific habitat relationships of Tillandsia landbeckii and its dependence on fog moisture inputs from the camanchaca suggest that these communities may serve as sensitive indicators of climate change in northern Chile . Existing areas of tillandsia dieback suggest increasing aridity and reduction of the intensity of the camanchaca in this century, consiste nt with floristic evidence from other sources.