| Popis: |
Very little information exist on lake environment in Northern Cameroon. The objective of this study is to determine the colonisation plant of Lake Dang using field and remote sensing data from LM, Landsat5, Landsat7 and Landsat8 images, over a 45-year period (1975-2020), spaced 15 years apart (1975; 1990; 2005; 2020). The method of diachronic analysis of satellite data was used and the supervised classification approach based on colour compositions and bands were chosen for class discrimination. The overall accuracies obtained ranged from 96.35 to 89.28%, followed by Kappa indices of 74.43 to 90.18% for the years 1975 and 2020 respectively. The results on the spatio-temporal dynamics of water bodies from 1975 to 2020 show an average annual rate of regression of the water surface of -1.35%/year, i.e. 0.099 km2/year, in favour of vegetation. The period from 1987 to 2002 shows a more marked evolution, with a rate of plant colonisation of 1.98%/year, i.e. 0.145 km2/year, compared to the periods from 1975 to 1990 (rate of plant colonisation of 0.85%/year, i.e. 0.062 km2/year) and 2005-2020 (1.23%/year, i.e. 0.090 km2/year). Today, 73% (5.376 km2) of the total surface area (7.365 km2) of the water body is colonised by vegetation. Moreover, bathymetry shows a maximum depth of 2.70 to 2.80 m, which is discriminating for a lake ecosystem in the Sudano-Guinean zone. Consequently, the preliminary results of this study shows that Lake Dang is marked by a strong eutrophication due to anthropic activities caused by agriculture, urbanization and non-rational deforestation which have strongly affected the occupation of the lake banks. |
