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 the roots of Erica arborea L. on a soil derived from alkaline and fine-textured marine sediments. Methods - Physical, chemical, mineralogical and biochemical properties of bulk soil and of the rhizosphere of Erica were characterized to evaluate its role on soil evolution. Results - Once the upper horizons had been decarbonated because of geomorphic and pedogenic processes, Erica colonised the soil and progressively modified it through the activity of roots. In the upper horizons, there was no difference between rhizosphere and bulk soil for pH, organic C and exchangeable Al and H. At depth, pH, organic C and exchangeable Al and H differed between rhizosphere and bulk soil. The weathering reactions induced by the Erica roots caused a relative quartz enrichment in the rhizosphere compared to the bulk soil. 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 poorly adapted as these horizons represented the boundary between acid and sub-alkaline soil environments. Conclusions - The activity of Erica roots modified soil properties so to produce more favourable conditions for itself and the rhizosphere microflora.