Survey of soil chemical properties across a landscape in the Namib Desert

A selection of soils were sampled in the Central Namib Desert to investigate the importance of landscape and associated plant communities on soil nutrient status. Soils were sampled in an ephemeral river, a wash, and at two dune sites. The soils in the lower landscape positions, the Kuiseb River and an associated wash, had significantly higher nutrient levels than those at the dune sites. These lower landscape positions also had the most stable plant communities,Faidherbia albidaandWelwitschia mirabilis, respectively. The two dune soils, which both support perennial herbaceous species, had extremely low nutrient levels. Only the wash showed nutrient enrichment of the soil under plants, as measured by a relative enrichment factor. This community is the most established, with plants being hundreds of years old; this time factor may be crucial for nutrient accumulation by plants in this extremely arid system. The lack of enrichment under theF. albidacommunity suggests that the fluvial inputs and exports, both organic and inorganic, tend to homogenize the nutrient levels within this system. These results indicate that soil nutrient levels in the Namib Desert are closely linked to landscape position and less so with the associated plant communities.