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Effect of Topographic Landforms on Vegetation Cover Density in Arid Landscape of the SE of Spain

AuthorsAfana, Ashraf
Issue Date23-Jan-2013
AbstractFollowing land tendency is a crucial aspect in the development of desertification monitoring systems. The density of the vegetation cover and its spatial structure constitute motivating properties in order to use as indices at the end of the tendency following. These properties of enormous important that permit to test changes at time scales similar to desertification, and on the other hand are relatively easy to record through remote sensing techniques. The general objective of the research work was to develop procedures in order to evaluate the vegetation properties with implications over land degradation such as the density and the spatial structure of the vegetation cover, utilizing remote sensing techniques. The new indices departed from a concrete hypothesis that is: Do relief forms (terrain classes) affect the density of vegetation cover distribution? Answering that question was achieved through studying the particular characters of the study area under consideration and the using of the digital form spatial available data that includes that describe the topography and the vegetation cover density in that area. The Tabernas Basin was selected as the representative site of the work, an area of about 1100 km2 that represent an arid environment. In that area we calculated the DEM through which we derived the topographic variables of the area. Then we realized a Numerical Taxonomy classification (NT) on the terrain attributes (raster overlays) to produce a subset of classes named as physiographic classes (topographic classes). After that, the NDVI of the area was calculated using the bands 3 & 4 of the Landsat TM. Afterward, a group of nonparametric statistical analysis was realized to analysis the relation between the terrain classes and the amount of the vegetation cover in each class (NDVI image). The results revealed that upper parts of the terrain possess more vegetation cover than mid and low ones, and mid parts possess more vegetation cover density than low parts but less than upper ones. In other words, the vegetation density shows a systematical distribution a long the hillslopes, which implies a clear relation between the spatial distribution of the vegetation cover density and the topographic landforms. The resulted relation was replicated over the same area but after dividing it to three levels in order to check whether altitude effect is a controlling factor in determining the vegetation cover density. However the results return again to agree with the above results. Finally, a field visit was realized to validate the results obtained from the NDVI image values, in order to check for the abnormal values of the NDVI and the changes in landuse took place through the 1996 until the 2002.
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