Khéloufi Benabdeli

The objective of this study is to contribute in assessing and mapping of the salinity risks level of soil and groundwater for irrigation in the Mina plain. The experimentation was carried out on a surface area of 4000 ha. Electromagnetic conductivity (EM) measurements and soil and well water samples were taken and analysed. The results showed an important spatial variability of the electrical conductivity (EC) of saturated paste extracts (ECe), which varied between 1.35 and 28.8 dS/m. The isovalues map of ECe was estimated by the regression equation and interpolated by the ordinary kriging (OK) method which showed that the area of saline soils (ECe > 4 dS/m) represented 90% of the study area. The results also showed poor to unsuitable well water quality. To find the risk of salinity and sodium, the water points were classified as C3S3 (2.5%), C4S2 (5%), C4S3 (30%) and C4S4 (62.5%). Spatial distribution maps of total dissolved solids (TDS), electrical conductivity of water (ECw) and sodium adsorption ratio (SAR) interpolated by inverse distance weighting (IDW) showed too high risk levels of ECw (>5000 μS/cm) and TDS (>3000 mg/l) occupying a large wellfield (70%); with regard to SAR (>18), 36% of the groundwater had a high risk of sodium. These results showed that the choice of tolerant crops, redevelopment of drainage systems and irrigation with less saline water should be designed for the sustainability of soil productivity and agro-ecosystems.

The accelerated and uncontrolled urbanisation in the coastal zone of Mostaganem is exclusively at the expense of agricultural and natural areas and is reflected in the aggravation of their degradation. The study area is a 62-km-long littoral to the west of Mostaganem and includes 11 municipalities. The Corine Land Cover nomenclature was used by exploiting data from Landsat satellite images over a 30-year period. The exploitation of statistics related to agricultural and forestry areas reveals a worrying dynamics. All spaces are under pressure mainly due to urbanisation. The phenomena of urbanization and coastalisation and the development of seaside tourism have increased the pressures on natural heritage to the point of compromising it. The analysis identified seven thematic object classes for the study area. An assessment of the dynamics of urban, forest and agricultural areas is an informative indicator of the sustainability of natural areas in the coastline of Mostaganem. The cultivated areas measured from 42,356 ha in 1985 to 38,301 ha in 2015,forest formations from 8207 ha to 9298 ha and urbanised areas from 2604 ha to 5049 ha. The dramatic land use change stimulated by rapid urbanisation in the study areas has resulted in a fundamental change in the landscape pattern. The thematic maps and the results obtained through different periods show that the predominant agricultural landscape has been gradually converted into urban areas.

Land cover change is the result of complex interactions between social and environmental systems which change over time. While climatic and biophysics phenomena were for a long time the principal factor of land transformations, human activities are today the origin of the major part of land transformation which affects natural ecosystems. Quantification of natural and anthropogenic impacts on vegetation cover is often hampered by logistical issues, including (1) the difficulty of systematically monitoring the effects over large areas and (2) the lack of comparison sites needed to evaluate the effect of the factors. The effective procedure for measuring the degree of environmental change due to natural factors and human activities is the multitemporal study of vegetation cover. For this purpose, the aim of this work is the analysis of the evolution of land cover using remote sensing techniques, in order to better understand the respective role of natural and anthropogenic factors controlling this evolution. A spatio-temporal land cover dynamics study on a regional scale in Oranie, using Landsat data for two periods (1984–2000) and (2000–2011) was conducted. The images of the vegetation index were classified into three classes based on Normalized Difference Vegetation Index (NDVI) values and analysed using image difference approach. The result shows that the vegetation cover was changed. An intensive regression of the woody vegetation and forest land resulted in -22.5% of the area being lost between 1984 and 2000, 1,271 km² was converted into scrub formations and 306 km² into bare soil. On the other hand, this class increased by around 45% between 2000 and 2011, these evolutions resulting from the development of scrub groups with an area of 1,875.7 km².

This work was being carried out in the steppe of remth (Hammada scoparia) in Oranian part of the Saharan Atlas (Tiout - south of Naama). The H. scoparia of Saharan group occupies the foothills south of the Saharan Atlas and glazes and hamadas of the northern part of the Sahara where it seems to find its optimum development. The objective of the study is the floristic and ecological characterisation of the steppe vegetation groups of H. scoparia after 4 years of enclosure grazing (Eg). For the past three decades, steppe of H. scoparia were completely overwhelmed, both in their structure and their operation by increasing the herd and the continued use of natural pastures using animal load significantly higher than the production potential of course, which is reflected by the reduction of their capacity for natural regeneration. Intervention measures that address this alarming situation are to foster the inverse process of degradation reconstruction and rehabilitation of degraded steppe rangelands by the technique of the Eg. The methodology involves a device that is composed of a series of transects that constitute a grid and allow to scan the whole website for Eg and part of the neighbouring paths. The results emphasise the interest and constructive impact of the Eg on plant diversity and the fight against the factors of degradation and desertification. This review highlights the importance of the technique of Eg for the rehabilitation and restoration of steppe rangelands in arid bioclimate.

La réduction de la pluviométrie dans les hautes plaines du sud de l'Algérie occidentale a provoqué de profondes modifications de l'occupation et de la gestion des espaces. L'activité économique de cette région est fortement conditionnée par les fluctuations climatiques et les modes traditionnels d'exploitation des surfaces agricoles. L'analyse de l'occupation actuelle des espaces et de sa dynamique permet d'appréhender les différentes contraintes appliquées à ces écosystèmes et de mesurer les incidences environnementales et sociales du changement climatique. L'objectif est de comprendre l'évolution des systèmes de production et de déterminer et maîtriser les paramètres qui influent sur leur dynamique pour une meilleure utilisation de ces espaces. L'incidence de la progression de l'aridité est perceptible à tous les niveaux : forte concentration de la population dans les centres urbains, réduction spatiale des formations végétales spontanées, augmentation des surfaces agricoles et de l'effectif du cheptel ovin menant la région vers un système de production agropastoral.Les hautes plaines de Sidi-Bel-Abbès sont impliquées dans tous les programmes de développement de la steppe. Elles se présentent comme une référence des régions du Sud Oranais et constituent, de ce fait, un espace idéal permettant de mesurer l'impact d'une politique d'aménagement ignorante des paramètres climatiques et de leurs fluctuations.

Une meilleure compréhension de l'évolution des modes d'utilisation des sols et du couvert végétal est une préoccupation majeure pour les pays dont les écosystèmes subissent des dégradations sévères. En effet, les dynamiques d'occupation des sols ont des implications directes sur la disponibilité des ressources naturelles. Notre étude menée sur les monts du Tessala en Algérie occidentale, en utilisant l'indice de végétation par différence normalisée (NDVI), met en évidence l'ampleur des changements du couvert végétal entre 1987 à 2007. Une évolution régressive prononcée du couvert végétal est constatée au sud-est et au nord-ouest des monts du Tessala, tout particulièrement dans la "forêt de Tessala", sur les communes d'Aïn-Thrid, Tessala et Sehala. Les principaux facteurs contribuant à la régression du couvert végétal sont : la déforestation (plus de 26 délits de coupe par an), le surpâturage (420 délits de pâturage illicite par an), les incendies de forêts (plus de 20 incendies par an) et l'érosion hydrique qui en résulte (environ 72 % des superficies sont concernées).

Le groupement à Hammada scoparia est une formation steppique caractéristique de l’Atlas Saharien de l’Algérie, se développe à une altitude de 800 à 1400m et occupe des sols sablo-limoneux à limono-sableux du piedmont sud de l’Atlas saharien, les glacis et les hamadas de la partie septentrionale du Sahara. Hammada scoparia est une espèce intéressante en tant qu’arbrisseau de 80 cm de hauteur et 10 cm de diamètre pour coloniser ces contrées arides avec une période de floraison qui s’étale du mois de Novembre jusqu’au mois de Janvier. Cette espèce rustique et résistante aux conditions difficiles (sécheresse, salinité, et faible précipitation), peut être recommandée dans la plantation de la steppe pour la sauvegarde et la conservation des sols.