the present study was conducted in the Morrocan Oulmes Central Plateau to assess the organic carbon stock (OCS) in the soil and biomass of the green oak ecosystem. Soil samples taken from green oak plots at the upper organomineral layer (<30 cm depth) were analyzed by conventional assay for the determination of carbon stock in each sample. Also, other soil physicochemical parameters namely pH, total nitrogen, total limestone, organic carbon, bulk density, texture, and stability of soil aggregates were studied. Aliquots of ten green oak trees were used to assess the carbon stock in the different compartments of the tree. The studied soil is slightly acidic to neutral with a pH ranging from 5.49 to 7.19. The texture of the studied area is loam. The soil organic carbon stock ranges from 16.03 t/ha to 97.33 t/ha with an average value of 40.07 t/ha. The total above-ground biomass of the green oak stands in the studied plots has an average value of 55.28 t/ha, and the average value of the total carbon mass is 31.06 t/ha.

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This paper aims to assess the impact of land-use evolution on water erosion in the Bouregreg subwatershed upstream of the Tiddas dam in the central Moroccan plateau. The methodology adopted is based on a diachronic study of land use between 1989 and 2019 from Landsat images of 30 m resolution. After the necessary pre-proc8essing, a classification of the images of the area using the Support Vector Machine (SVM) algorithm was performed and validated via the data from the processing of aerial photographs from 1989, Google Earth satellite images at a high resolution from 2019 and field validation outputs. The predictive approach falling under the guidelines for mapping and measuring water erosion processes has been exploited to assess the evolution of potential areas for erosion (PAP/CAR guidelines). The results highlight the forest's regression of 5% during the 30 years and the increase in the stages of degradation, namely the rangeland of 6%. The level of erodibility occupying the subwatershed is high to extreme, totalling 63% of the total area. The high to very high levels of soil protection have experienced a regression in their areas ranging from 30% in 1989 to 18% in 2019. The areas vulnerable to a very high level of erosion have seen an increase from 21% in 1989 to 38% in 2019. These results clearly show the worrying state of the area's vulnerability, and thus, make it possible to provide decision-makers with scientific elements that can guide the planning and implementation of action programmes for the protection of the Tiddas Dam.