28 research outputs found
Integrating Sentinel-2 Data and PAPCAR Model to Map Water Erosion: Case of Beni Boufrah Watershed
Water erosion causes significant economic losses linked mainly to the silting up of dams and losses in soil productivity, these consequences will increase if soil and water conservation actions associated with development actions are not undertaken. The present work aims to evaluate the water erosion in the basin of the Beni Boufrah located in the Northern part of Morocco. The hierarchy of this basin in plot according to the degrees and the tendencies of the erosion was made using the qualitative PAP/CAR approach (Programme dâActions Prioritaires/Centre dâActivitĂ©s Regionales) which is based on the integration of the factors influencing the water erosion, such as the slope, lithology and/or pedology, vegetation cover and land use. This work was conducted in three stages, the first one being predictive based on the analysis of the natural factors influencing water erosion and the processing of databases of developed maps. The second so-called descriptive stage is based on the mapping of different forms and processes of soil loss that occur in the study area. The last step, it allows the integration and the combination of the results of the two previous steps. Its purpose is to provide a precise cartographic product that reflects the reality of the state of soil degradation and the future evolution of erosion. The consolidated erosion map shows that more than half of the basin area (53%) is affected by medium-level erosion, 13% is affected by high erosion level, and 15 % is affected by low-level water erosion. Low-intensity erosion occurs along the river in areas where the slope and lithology favour runoff. The trend map is the final result of the integration phase, it describes erosion trends in the different parts of the basin and is, therefore, a tool to guide decisions on land use planning and tillage methods to limit the risk of water erosion in the basin.
Keywords: Oued Beni Boufrah, water erosion, PAP/CAR, erosive states, erosion trend
Impact of climate change on potential distribution of Quercus suber in the conditions of North Africa
Climate change, which is expected to continue in the future, is increasingly becoming a major concern affecting many components of the biodiversity and human society. Understanding its impacts on forest ecosystems is essential for undertaking long-term management and conservation strategies. This study was focused on modeling the potential distribution of Quercus suber in the Maamora Forest, the worldâs largest lowland cork oak forest, under actual and future climate conditions and identifying the environmental factors associated with this distribution. Maximum Entropy approach was used to train a Species Distribution Model and future predictions were based on different greenhouse gas emission scenarios (Representative Concentration Pathway RCPs). The results showed that the trained model was highly reliable and reflected the actual and future distributions of Maamoraâs cork oak. It showed that the precipitation of the coldest and wettest quarter and the annual temperature range are the environmental factors that provide the most useful information for Q. suber distribution in the study area. The computed results of cork oakâs habitat suitability showed that predicted suitable areas are site-specific and seem to be highly dependent on climate change. The predicted changes are significant and expected to vary (decline of habitat suitability) in the future under the different emissions pathways. It indicates that climate change may reduce the suitable area for Q. suber under all the climate scenarios and the severity of projected impacts is closely linked to the magnitude of the climate change. The percent variation in habitat suitability indicates negative values for all the scenarios, ranging â23% to â100%. These regressions are projected to be more important under pessimist scenario RCP8.5. Given these results, we recommend including the future climate scenarios in the existing management strategies and highlight the usefulness of the produced predictive suitability maps under actual and future climate for the protection of this sensitive forest and its key species â cork oak, as well as for other forest species
Spatio-temporal analysis of North African forest cover dynamics using time series of vegetation indices â case of the Maamora forest (Morocco)
North African forest areas play several roles and functions and represent a heritage of great economic and ecological importance. As a result of global changes, that act independently or synergistically, these areas are currently undergoing a pronounced degradation and their productivity is decreasing due to several factors. This work aims to characterize spatio-temporal dynamics of vegetation within the Maamora forest. This forest is considered as the most extensive cork oak woodland in the world and is divided, from west to east, into five cantons A, B, C, D and E. The data, extracted between 2000â2021 from MODIS NDVI/EVI images of 250 m, were analyzed using statistical parameters with the Pettitt homogeneity and the Mann-Kendall trend tests, with their seasonal and spatial components, in order to better consider the vegetation distribution of this forest. Results show a clear temporal and spatial (inter-canton) variability of vegetation intensity, unrelated to the continental gradient. In fact, recorded mean values in cantons C and E are significantly higher than those of cantons B and D respectively. This is confirmed by both regressive and progressive trends, which were identified respectively from the months of March 2012 and October 2008, in the data series of cantons B and E successively. Spatially, the regressive dynamic remains generalized and affects more than 26.7% of the Maamoraâs total area with extreme rates (46.1% and 14.0%) recorded respectively by the two aforementioned cantons. Similarly, all the stand types in canton B show the highest regressive rates, especially the cork oak regeneration strata (75.4%) and the bare lands (86.1%), which may explain the positive tendencies identified by the related series during the fall season. However, the cantons C and E record the lowest rates, respectively, for natural stands of cork oak and artificial plantations. These results highlight also the absence of a causal relationship between the contrasting vegetation dynamics of the Maamora and the climatic conditions, expressed here by the continental gradient. However, they do highlight the effects of other factors, particularly those of a technical nature
Impact of climate change on forest resources: Case of Quercus rotundifolia, Tetraclinis articulata, Juniperus phoenicea, J. oxycedrus, J. thurifera and Pinus halepensis
Forest resources in the Ourika watershed are subject to several anthropogenic and climatic degradation factors. As for the human factor, this degradation of forest resources is explained by the bad practices exercised by the local population expressed by the cutting of live wood, carbonization, and overgrazing. In terms of the climatic factor, the decrease in the amount of rainfall and the increase in temperature contribute to the exacerbation of the degradation of these resources. In order to better understand the evolution of plant cover in a changing climate context, this study highlights an assessment of the impact of climate change on forest dynamics based on a process-based model at the forest landscape scale which makes it possible to simulate the changes according to growth, succession, disturbances (fire, wind, insects, etc), forest management, and land use change. This analysis is based on the use of the LANDIS-II model and the PnET-succession extension. Projections of the dynamics of forest communities are made using climate projections from the Japanese global circulation model adopted by Morocco (model for interdisciplinary research on climate â earth system models) and this by adopting the two climate scenarios , representative concentration pathways 4.5 and 8.5. The results obtained highlight the spatial distribution of the ecosystems studied after 100 years with a quantitative evaluation of the total average biomass of these resources as a function of climatic disturbances. In general, the estimated total biomass will decline over the coming years under the joint effect of the climate change and the aging of forest stands, while on the other hand, the distribution of potential areas for species settlement remains independent of the effect of these climate changes
Impact du cordon sableux déposé à l'embouchure du site Ramsar de l'estuaire de l'Oued Massa (Maroc) sur l'hydrologie et l'avifaune.
SituĂ© sur un des principaux axes de migration des oiseaux dâeau entre lâEurope et lâAfrique, lâestuaire de lâoued Massa, inscrit dans la liste Ramsar depuis 2005, a connu des modifications hydrologiques importantes, Ă la suite de lâinstallation en amont du barrage Youssef Ben Tachfine en 1972. En effet, lâinstallation de ce barrage a induit le dĂ©pĂŽt dâun cordon de sable au niveau de lâembouchure, sĂ©parant les eaux de lâoued de celles de lâocĂ©an atlantique et transformant le site dâun Ă©cosystĂšme estuarien en Ă©cosystĂšme lagunaire. Le site est aussi le siĂšge de changements irrĂ©guliers, enregistrĂ©s lors de disparitions temporaires du cordon de sable survenues Ă la suite des lĂąchĂ©s de barrages lors des prĂ©cipitations abondantes comme câĂ©tait le cas en 1983, 1992, 1996 et 2010. Ce travail de recherche vise Ă Ă©tudier lâeffet des modifications de lâĂ©cosystĂšme Ă la suite de la disparition du cordon du sable de lâembouchure, sur lâĂ©volution des paramĂštres physicochimiques du milieu et sur les oiseaux frĂ©quentent le site. Pour ce faire plusieurs paramĂštres physicochimiques de lâeau (pH, oxygĂšne dissous, tempĂ©rature, salinitĂ©, azote ammoniacal, ortho-phosphate et nitrates) ont Ă©tĂ© mesurĂ©s avant (2009) et aprĂšs (2010) la derniĂšre disparition du cordon de sable survenue en fĂ©vrier 2010. Concernant lâinfluence des changements de lâĂ©cosystĂšme sur lâavifaune, elle a Ă©tĂ© Ă©valuĂ©e grĂące au suivi de 7 espĂšces dâoiseaux parmi les plus caractĂ©ristiques de ce site Ramsar. Les rĂ©sultats obtenus montrent que le passage de lâembouchure dâun Ă©tat lagunaire vers un Ă©tat estuarien Ă la suite de la disparition du cordon sableux sâest traduit principalement par lâamĂ©lioration de la qualitĂ© des eaux par accroissement des valeurs de lâoxygĂšne dissous. Le milieu a connu aussi une augmentation de la salinitĂ©. Concernant les oiseaux dâeau, les sept espĂšces Ă©tudiĂ©es ont enregistrĂ© une frĂ©quentation du site trois ans avant et trois ans aprĂšs la destruction des dĂ©pĂŽts de sable. Toutefois, il apparait clairement que ces modifications ont eu un effet sur les effectifs de certaines espĂšces hivernantes Ă lâembouchure de lâoued Massa. Ce travail constituera une base importante permettant, avec dâautres Ă©tudes complĂ©mentaires, de mieux gĂ©rer le rythme des lĂąchĂ©s de barrage lors des prĂ©cipitations abondantes
Annual dynamics of glycogen, lipids and proteins during the sexual cycle of Perna perna (Mollusca: Bivalvia) from south-western Morocco
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Cytotoxic T Lymphocytes Specific for HIV-1 gp160 Antigen and Synthetic P18IIIB Peptide in an HLA-A11-Immunized Individual
Cytotoxic T cell determinants should be an important component of an anti-human immunodeficiency virus (HIV) vaccine. The epitopes of proteins can be defined with short synthetic peptides for class I-restricted CTLs. An immunodominant CTL epitope from the HIV-1 IIIB envelope protein gp160 comprising 15 amino acids (residues 315-329: RIQRGPGRAFVTIGK) (P18IIIB) has been identified that is recognized by class I MHC molecule H-2d-restricted murine CD8+ CTLs. We have investigated the epitope specificity of anti-HIV-1 CTLs in immunized individuals and we found that the CTL response was restricted by more than one class I MHC molecule, including HLA-A2 and HLA-A3. In the present work, we also show that the response against P18IIIB peptide is restricted by the HLA-A11 molecule in an individual immunized by vaccinia virus expressing gp160 protein. This peptide could thus be recognized in association with different HLA class I allotypes. This work has implications for vaccine strategies, using the P18 peptide. © 1994, Mary Ann Liebert, Inc. All rights reserved.SCOPUS: ar.jinfo:eu-repo/semantics/publishe
Wastewater toxicity of tannin- versus chromium-based leather tanneries in Marrakesh, Morocco
The toxicity of leather tanning wastewater from a traditional tannery (TT), based on vegetable tannin (VT) was compared to wastewater from a tannery combining the use of chromium-based tanning (CT) with VT-based tanning operations. Wastewater samples were collected in Marrakesh, Morocco, from a TT and a CT plant, and from some sampling points in Marrakesh urban sewer, and the VT content was measured in wastewater samples. A set of bioassays were utilized testing wastewater toxicity in sea urchin (Paracentrotus lividus) embryos and sperm, Daphnia magna, and marine microalgae (Dunaliella tertiolecta). Toxicity endpoints included: a) developmental defects, sperm fertilization success and offspring damage in sea urchins; b) D. magna immobilization, and c) algal growth rate. Toxicity tests on TT and CT effluents (TTE and CTE) were run at dilutions ranging 0.1 to 2% (sea urchins and algae) or up to 12% in D. magna. Parallel bioassays were run on VT extract (VTE) at nominal tannin concentrations ranging 0.1 to 10 mg/L. The results consistently showed a higher toxicity of CTE compared to TTE. The effects in sea urchin and algal bioassays showed monotonic concentration-related trends for CTE toxicity, whereas TTE displayed a trend suggesting a hormetic effect at TTE dilutions of 0.1 to 0.3%, followed by toxic effects at TTE levels 1%. The same trend was observed for VTE, consistent with a prevailing role of tannin in TTE-associated effects. The relatively low wastewater toxicity of VT-based tanneries may prompt a renewed interest in utilizing this leather tanning process
Acute toxicity of trichlorfon to juvenile yabby Cherax destructors (Clark) and selected zooplankton species
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