Spatial distribution of and topographic controls on Tillandsia fog vegetation in coastal southern Peru: Remote sensing and modelling

Abstract

Fog-dependent vegetation communities (lomas) occur in disjunct populations in the coastal desert of Peru and northern Chile. Epiarenic species of Tillandsia develop characteristic metre-scale vegetation patterns which allow their distribution to be mapped in high-resolution satellite images. In combination with digital elevation models, topographic controls on their distribution are deduced. Dense Tillandsia lomas in the Pisco–Acarí sector of the Peruvian coastal desert occur at elevations between 467 and 1129 m; sparse populations have a slightly wider elevation range but are spatially much more extensive. Mean slope and aspect of dense Tillandsia lomas are 3.5° and 227°, respectively; however, scatter is large. Modelling based on the topographic properties of mapped dense Tillandsia lomas results in a much larger surface area than actually occupied by Tillandsia, implying that there must be other limiting factors besides local topographic controls. Comparison of the modelling results with the mapped distribution in conjunction with satellite images and digital elevation models indicates that the factors which limit the actual distribution of Tillandsia are (i) distance from the coast together with regional-scale lee situations behind the Cordillera de la Costa, (ii) local lee situations behind small topographic obstacles and (iii) wind strength and/or aeolian sediment transport.