Changes induced by the roots of Erica arborea L. to create a suitable environment in a soil developed from alkaline and fine-textured marine sediments

Background and Aims We report on the modifications induced by roots of Erica arborea L. on a soil derived from alkaline and fine-textured marine sediments. Methods Bulk and Erica rhizosphere were characterized physically, chemically, mineralogically and biochemically to evaluate the role of this species in soil evolution. Results Once the upper horizons had been decarbonated because of geomorphic and pedogenic processes, Erica colonised the soil and progressively modified it by the activity of its roots. In the upper horizons there was no difference between rhizosphere and bulk for pH, organic C, and exchangeable Al and H, while in depth rhizosphere and bulk differed on these parameters. The weathering exerted by the Erica roots was manifested by the higher quartz content in the rhizosphere than in the bulk because of indirect enrichment. In the E, EB and Bw horizons, the microbial community of the rhizosphere appeared better adapted than in the underlying 2Bw horizons where the rhizospheric microorganisms were scarcely adapted as these horizons represented the boundary between acid and sub-alkaline soil. Conclusions Erica, through the activity of its roots, made a great effort to modify soil properties so to produce favourable conditions for itself and the microflora harbouring the rhizosphere.