Considering the effects of land use change during 1990s in the Tell mountains of northern Algeria, a research programme was developed by the Algerian INRF and the French IRD, to study the influence of land uses and cultural practices on runoff, erosion, soil fertility, and soil organic carbon (SOC) dynamics at the scale of runoff plots (100 to 220 m 2). The study included comparisons between traditional and improved land management systems for the principal soils of northern Algeria. The field experiments were conducted: (i) from 1993 to 1998 in the Beni-Chougran mountains near Mascara, in western Algeria; (ii) from 1991 to 2001 in the Tlemcen mountains in western Algeria; and (iii) from 1988 to 1992 around Medea in central Algeria. These regions are representative of the Tell mountains with regards to landscape, erosion manifestations (sheet erosion, gullies, floods and mass movements), and the various programmes of soil conservation since 1950s. The plots were set up on three soil types: (i) clayey brown Vertic soils on marl (Vertic Haploxeroll in Mascara and Tlemcen, Typic Haploxerert in Medea); (ii) brown calcareous soils on sandstone or limestone (Typic Haploxeroll in Mascara, Tlemcen and Medea); and (iii) red Fersiallitic soils on sandstone (Typic Haploxerept in Tlemcen and Medea). Data showed that at the plot scale, runoff and sheet erosion risks were generally moderate in the semiarid mountains of northern Algeria, even when the fields were cropped on steep slopes. Sediments were richer in OC than the topsoil (0-10 cm depth), and that this enrichment increased with soil surface cover (i.e., bare plots
