IMPACTS DES CHANGEMENTS CLIMATIQUE SUR LES COMPOSANTES DU SYSTÈME OVIN

Abstract - Pastoral systems occupy two-thirds of the world's arid lands with higher rates of desertification than other land uses (Neely et al., 2009). Therefore, agriculture has been and will certainly is affected by the negative impacts of climate change, this phenomenon which affects seriously water resources, ecosystems and agro-systems. The expected succession of dry years will lead to a decline in livestock (sheep, cattle and goats) by 80% in the central and southern parts of the country and 20% in the north (GEREP-Environnement, 2009). Among the governorates studied, the governorate of Siliana is declared as the most affected zone by desertification in Tunisia.The main theme of this study aims to characterize the climatic changes over 30 years in the semiarid region of Tunisia. In order to identify the consequences of climate change on grasslands and pastures and subsequently the productivity of small ruminants.The statistical analyzes was carried out by the statistical software SAS 0.9. The effect of several factors on the evolution of the numbers, the area of ​​occupations of the soil which is an indicator on the nature of the orientation of agricultural area and the variability between governorates were studied. Variance analysis were made to understand the changes of the cultivated area, which is indicator on the evolution of the agricultural practices in the study zone, and to compare the differences between governorates and years. The results show that climate change has direct and indirect effects on the sheep farming situation in the region studied. It has clearly shown that the studied governorates do not have the same vocation of breeding. The governorate of ElKef is the most affected by these climatic changes. This leads to develop a simulation tool that allows predicting the impact of climate change on sheep farming.

Keywords: Climate change, sheep, forage, area, farming.

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Abstract - The objective was to evaluate the effect of three water treatments on biomass by monitoring water status as an indicator of stress. The study consists of applying three water treatments (100, 50 and 25% field capacity (FC)) on one-year-old olive plants (Olea europaea L. cv Meski) during 42 days in a greenhouse under semi-controlled conditions. The evaluation of olive tree response was carried out by monitoring water and osmotic potentials, osmotic adjustment, relative water content and accumulation of dry matter.The water potential decreased by 16 and 28% compared to control plants (T100%) at the end of the experiment, respectively for T50% and T25% plants. The osmotic potential decreased by 50 and 64% compared to control plants respectively for T50% and T25% plants to reach -4.54 and -4.98 MPa due to regression of water stock. As a result, the osmotic adjustment increased to 1.51 and 1.95 MPa respectively for T50% and T25% plants at the end of the experiment. Olive tree decreases its water and osmotic potentials and the osmotic adjustment would be more important according to the progression of the degree of stress. T50% and T25% plants had a passive osmotic adjustment of 79 and 89% respectively. Control plants accumulated more dry matter in the roots and stem, while the root/ shoot ratio seemed indifferent to water stress. The water restriction has affected root and stem dry matter in favor of leaves, the first operator of photosynthetic activity.These results indicate that a water restriction for Meski cultivar implies a specific adaptation characterized by a reduction in osmotic potential involving an increase in osmotic adjustment and a shift in the distribution of dry matter maintaining the leaves dry matter of stressed plants similar to those of control plants at the expense of roots and stem to ensure photosynthetic activity.

Keywords: Olea europaea L., Water stress, Leaf water potential, Leaf osmotic potential, Relative water content, Root/shoot ratio.

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Abstract - Tunisia is characterized by a semi-arid climate over more than 90% of its territory with irregular and high spatial variability of rainfall. This constitutes a major constraint limiting agriculture development which depends on the availability of water resources. The assessment and the effective management of water resources in a territory require then extensive knowledge of involved hydrological processes as well as their temporal and spatial scales. This paper discusses the issue of mobilization and hydrological functioning of the Rmel watershed to get an efficient management of water resources in case of scarcity or extreme events using modelling tool. This watershed (675 km²) is situated in North-East Tunisia with average annual rainfall of 420 mm and was equipped in 1998 with a dam. Data on rainfall collected at 12 rainfall stations during the period 1998-2013 are analyzed and used to build a coherent series of monthly rainfalls. In a second step, rainfall-runoff modelling using SWAT Model was used to estimate runoff and water budget of the dam. The Nash criterion is about 85% for calibration and validation. For the tow scenarios with an increase of the annual crops and farmland areas, we noticed that the watershed response was affected in the same way, causing an overestimation of water budget and especially the runoff peaks. The use of the model to make prediction of stream flow using downscaled climatic data from ARPEGE for the period 2060-2080 was discussed. For SWAT model, the estimated stream flow shows a tendency to increase the runoff process explained by the increase of the rainfall intensity. We noted that the implementation of SWAT model is able to represent efficiently the actual hydrologic runoff phenomenon and to predict watershed hydrological behaviour in the future. Thus, this work could be considered as a new tool decision support that can contribute to better management of natural resources in semi-arid environment.

Keywords: Hydrogical modeling, streamflow, Rmel watershed, Tunisia, climate change.

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Changements climatiques et zones humides en Algérie: vulnérabilité et enjeux de conservation (cas de Béni-Bélaïd)

Abstract - Based on the example of the Beni-Bélaïd wetland, this contribution is concerned with the impact of climate change on wetlands in Algeria. Despite their high heritage value and their multiple roles they perform, the wetlands are considerate as the most degraded ecosystem in our country under natural and anthropogenic pressure. Since the 1990s, the climate change has direct and indirect adverse impacts on the water resources. Thus, the changes in climate conditions will affect the availability of freshwater and can significantly alter the nature and function of the wetlands and their faunistic and floristic diversity. Their conservation represents a real ecological and economical challenge because they need to be managed efficiently and sustainably in order to keep their values and diversity.

Keywords: Issue of climate change, Water resources, Faunistic and floristic iversity, Sustainable management, Beni-Bélaïd wetland.

Résumé - La présente contribution, qui s’appuie sur l’exemple de la zone humide de Béni-Bélaïd, traitera l’impact des changements climatiques sur les zones humides en Algérie. Malgré leur haute valeur patrimoniale et en dépit de la multiplicité des fonctions qu’elles assurent, ces dernières constituent un écosystème qui est le plus dégradé dans le pays sous l’effet des pressions naturelles et anthropiques. Depuis les années 90, les changements climatiques ont des impacts néfastes directs et indirects sur les ressources en eaux. Ainsi, les changements des conditions climatiques perturbent la disponibilité de l’eau et peuvent modifier fortement la nature et la fonction des zones humides, y compris le patrimoine faunistique et floristique qui s’y abrite. Sa préservation représente un enjeu écologique et économique d’importance capitale, car elles ont besoin d’être gérées rationnellement et durablement pour garder leurs grandes variétés de valeurs et de fonctions.

Mots clés: Enjeux deschangements climatiques, Ressources en eaux, Patrimoine faunistique et floristique, Gestion durable, Zone humide de Béni-Bélaïd.

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Prospection et inventaire de l’agrodiversité dans les oasis traditionnelles de Gafsa

Abstract - The present paper discussed the prospecting and inventory of agrodiversity in the traditional oases of Gafsa. Our working methods were based on surveys carried out on farms according to a questionnaire. The inventory of local species and varieties (richness of the species, richness of the varieties) was carried out. Gafsa oases (Sakdoud, Ksar, Lela, Gafsa and El Guettar) are characterized by a high diversification of local species and varieties. The result of our investigations allowed us to identify 23 date palm varieties and 11 fruit trees species. Fruit trees crop is mainly based on olive with a percentage of 62 % of total, with a dominance of the '' Gafsi '' variety (85%). Date palm represents a percentage of 18.48 % of total. We surveyed 13 species of vegetable crops where cultivated. The most common crops are pepper, bean, chard and turnip. The study of the agrodiversity showed that the plant material of some local varieties (cuttings, seeds, etc.) is endemic to these oases. The extension of some crops such as the ‘’Gafsi’’ olive tree in El Guettar constitute a threat of erosion and loss of diversity.

Keywords: Oasis, Agro-diversity, Prospecting, Date palm, Fruit species.

Résumé - La présente étude est une contribution à la prospection et l'inventaire de l'agrodiversité dans les oasis traditionnelles de Gafsa. L'étude est basée sur la réalisation d'enquêtes auprès des agriculteurs et des paysans. L'inventaire des variétés locales (richesse spécifique, richesse variétale, etc.) a été réalisé. Les oasis de Gafsa (Sakdoud, Ksar, Lela, Gafsa et El Guettar) sont caractérisées par un niveau de diversité très considérable.. On a noté la présence 23 variétés de palmier dattier et 11 espèces d'arbre fruitier. La culture arboricole est basée principalement sur l'oléiculture avec un pourcentage de 62 %, avec une dominance de la variété ''Gafsi'' (85 % du total), le palmier dattier vient en deuxième place avec un pourcentage de 18,48 %. Il est a noté également que quelques parcelles ont montré la présence des cultures maraîchères où 13 espèces ont été recensées. Les cultures les plus fréquentes sont la blette, le piment, le navet et la fève. Il en ressort de ce travail que, le matériel végétal de certaines variétés locales (rejets, boutures, semences, etc.) cultivées dans ces 5 oasis sont localisées. L’extension des cultures monovariétale : cas de l'olivier ''Gafsi'' à El Guettar, constituent une menace d'érosion et une perte de la diversité.

Mots clés: Oasis, Agrodiversité, Prospection, Palmier dattier, Espèces Fruitières.

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Effet de la plantation d’une espece fourragere dans le sud-ouest algerien a climat semi aride

Abstract - Desertification concerns the arid and semi-arid steppes, which are the privileged space for extensive sheep farming, which results in the reduction of biological potential and the breakdown of ecological and socio-economic balances. The objective of this research was to quantify the positive effect of the planting of the species Atriplexcanescens on soil fertility. 54 soil surveys were carried out in the degraded steppe trails of the commune of Ain Chouhada (wilaya of Djelfa).Chemical analyzes were carried out inside and outside a plantation at Atriplexcanescens. We note a significant improvement in pH. However, total nitrogen seems not to respond positively to the presence of this species. Our study shows that the introduction of Atriplex canescens in the algerian steppe allows an improvement of soil fertility. We suggest the selection of a variety more adapted to the Algerian steppe ecosystems with the aim of multiplying and diversifying the forage plantations in the formations where the degradation is very advanced. 

Keywords: Atriplex, steppe, soil, Ain Chouhada, plantation.

Résumé - Au sujet de cette étude est la désertification concernante les steppes arides et semi-arides, espace privilégié de l’élevage ovin extensif qui se traduit par la réduction du potentiel biologique et par la rupture des équilibres écologiques et socio-économiques. L’objectif principal est de quantifier l’effet positif de la plantation de l’espèce Atriplex canescens sur la fertilité du sol. Les 54 relevés pédologiques ont été effectués dans les parcours steppiques dégradés de la commune d’Ain Chouhada (wilaya de Djelfa). Des analyses chimiques ont été testées à l’intérieur et l’extérieur d’une plantation à Atriplex canescens. Nous notons une amélioration significative pour le pH. Cependant, l’azote total semble ne pas répondre positivement à la présence de cette espèce. Notre étude montre quel’introduction d’Atriplex canescens dans la steppe algérienne permet une amélioration de la fertilité du sol. Nous suggérons la sélection d’une variété plus adaptée aux écosystèmes steppiques algériens dans le but de multiplier et diversifier les plantations fourragères dans les formations où la dégradation est très avancée.

Mots clés: Atriplex, steppe, sol, Ain Chouhada, plantation.

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