A conceptual model of coastal dune ecology in arid climate zones

Abstract

The environmental conditions that control the composition and abundance of vegetation and its spatial distribution pattern in arid-climate dunes are poorly understood, in contrast to dunes in tropical and temperate climates. This study aims to develop a spatially explicit conceptual model that integrates the main environmental factors (sand mobility, salinity, distance from the coast and topography) and the precise location of plant individuals. The study area consisted of a 100 x 400 m plot located on the sealand gradient in the dune system of Famara, Lanzarote (Canary Island, Spain). A digital elevation model was obtained by drone flight. A digital model of sand mobility was obtained using LiDAR data (2009 and 2015) from the Spanish National Geographic Institute. Electrical conductivity was measured in soil samples and a digital salinity model was generated. All nebkhas (discrete dunes formed by sand deposition around isolated or discrete plants) were geolocated using differential GPS, and species composition and abundance were recorded. Species richness and the Shannon index were also calculated. The results show that species composition and abundance are primarily determined by sand mobility. All species are perennial and salt-tolerant. The most mobile areas show larger nebkhas formed by a single species, Traganum moquinii. As mobility decreases, the number of nebkhas increases and their size decreases, supporting more diverse vegetation. Our model highlights the importance of studying the vegetation pattern of arid-climate dunes along mobility gradients from beach to inland.