The objective of this study is to map the land cover units (LCU) of the Plateau of Allada from the supervised classification by the maximum likelihood method of Landsat multi-spectral images (TM 1986, ETM+ 2000 and OLI 2020) and to highlight their evolutions by analyzing the areas and the rates of change. The approach used combines image pre-processing, identification of land use unit classes, construction and execution of supervised classification by the maximum likelihood method and quantification of change. All of these treatments applied to the images, allowed us to obtain the land use maps in 1986, 2000 and 2020 with five land use classes (forest/gallery/swamp, plantation, mosaic/fallow/crops, dwellings/bare ground, and water yard). Analysis of the dynamics of the land use units from 1986 to 2020 shows a progressive trend in the area of the mosaic/crop/fallow (25.97%) and habitat/bare soil (10.51%) classes and a regressive trend in the forest/gallery/swamp (-5.82%), plantation (-0.13%) and water (-0.25%) classes. Quantification of change from 1986 to 2020 is assessed by an estimated rate of change (Tc) of -5.82% (forest/gallery/swamp); 1.38% (mosaic/fallow/crop); 2.79% (dwellings/bare ground); -0.13% (plantations) and -0.25% (watercourse). This evolution is due to the expansion of the housing/bare soil and the mosaic/fallow/crops areas. This is the result of the strong human pressure on the vegetation formations. These results constitute a decision-making tool for the sustainable management and urbanisation of the Plateau of Allada.
The present research aims to study the variability of the NDVI in the step of annual times in the catchment area of Upper Ouémé between 2000 and 2015. Vegetation Index data is analysed to highlight the spatial variation time of vegetation. The MODIS 250 m resolution are used to analyse the details of the dynamics from 2000 to 2015. Generally, vegetative activity in the Upper Ouémé, declined during the 2000-2015 time series. The spatio-temporal dynamics of vegetation brought together the months of the year, according to homogeneous dynamics. So some months, like those of July-August, are marked by a significant improvement in the vegetation. Others, contrariwise, knows a reverse situation. These are the months from November to February. The Pettit test applied to the series of NDVI MODIS shows that between 2000 and 2015, the data are not homogeneous and that there are dates from which the changes were observed in the data. The year of greater plant production is 2003. As for the year to the smaller plant activity, it corresponds to 2005.
Zouzounkan massive is one of southern Benin forests whose management is done communally in the transition zone between the crystalline basement and the sedimentary soil. The present study is an application of satellite imagery and statistical modeling to the assessment of Zouzounkan forest cover states since the year 1990 to 2010 . It appears that there is a negative correlation between bare soil and vegetation massif Zouzounkan (-0.74 to clear forests and woodlands and -0.33 for tree and shrub savanna) . The mosaics of crops and fallow induce a negative correlation of -0.29 to clear forests and woodlands. Soil erosion leads to turn a negative correlation of -0.11 with tree and shrub savannah. 2 linear state functions were achieved through factor analysis on the basis of two factorial axes explaining 100% of the variance. The factorial axis 1 is materialized by a linear function f(x) = 0,997 Se + 0,969 FcSb + 0,960 Ma - 0,865 Sd - 0,778 Shs - 0,521 Mcj ; where Se = Soils altered by erosion; fcsb = Clear forest and savanna woodland ; Ma = Wetlands ; Sd = bare floors ; Shs = Savanna Grassland ; Mcj = mosaics of crops and fallow. The factorial axis 2 is represented by F(x) = 0,24 FcSb -0,983 Saa + 0,854 ; With Saa = tree and shrub Savannah. Frome the diagram of components in space after rotation, we deduce that the increase 0.865 units of bare floors or 0.521 units mosaics of crops and fallow causes a degradation of 0.969 units of woodland and savanna Woodland. Urgent mesures of reforestation, erosion control and forest eve well-organized are essential for the sustainability of massive Zouzounkan agroecosystems.