The influence of Saharan dust deposits on La Palma soil properties (Canary Islands, Spain)

The significance of Saharan dust deposits for ecosystems has been demonstrated in several studies, showing its influence on pedogenesis and soil chemical and physical parameters by the addition of nutrient elements. This contribution is especially important for volcanic soils poor in plant-available phosphorous as those of the island of La Palma (Canary Islands, Spain). Thus, this study investigates the spatial distribution of Saharan dust on the island, and determines its influence on soil properties and thus on the ecosystem of the island. Since silt-sized quartz is not autochthonously formed on the island, it served as a reliable indicator for Saharan dust. Quartz was identified and quantified using X-ray diffractometry. The influence of Saharan dust additions on soil properties was assessed by texture analyses and analyses of plant-available phosphorous, an element strongly limiting plant-growth on the island due to its fixation in the structure of amorphous volcanic clay. A luff–lee-effect revealed significant influence on dust distribution, whereas small geomorphologic structures as hollows and mounds hardly influenced the dust distribution pattern. A positive correlation of quartz content with the proportion of the grain size fraction 0.5–10 μm demonstrates an influence on soil physical properties, apparently influencing available water capacity. Furthermore, our data suggest an increasing content of plant-available phosphorous with a rising amount of Saharan dust in the soils. Thus, the input of Saharan dust influences soil fertility of La Palma and is an important factor regarding the fragility of the La Palma ecosystems.