| المستخلص: |
During the past 30 years, the Normalized Difference Vegetation Index (NDVI) has been widely used for vegetation mapping and monitoring land-cover change in semi-arid regions. Most of Libya is desert, but semi-arid lands occupy many parts in the north, near the Mediterranean Sea. The overall aim of this paper is to use remote sensing technique (NDVI) for monitoring vegetation degradation in Al-Jabal Al-Akhdar Region in Libya. In this paper the Pathfinder AVHRR Land (PAL), SPOT Apparent Green Cover Percentage data and MODIS Vegetation index are used to monitor the vegetation cover change in the area. In this work, we demonstrate the possibility of use of only long term NOAAAVHRR NDVI time-series data, without need to any precipitation data, for assessing desertification conditions in Jabal Al-Akhdar Region in Libya. It can be concluded that northern parts of the area receive the greatest amount of rainfall towards the Mediterranean Sea. Rainfall occurs mainly between October and May, it agreed well with the spatial pattern of NDVI within monthly averaged of vegetation, which start increasing rapidly and reached a greater amount during spring (March-May), and decreased during June to September. Annual rainfall in the study varies between the south and north of the area. It was agreed with spatial distribution patterns of NDVI which ranges from less than -0.3, 0% and 0.00 in the southern part of the area to more than 0.10, 16% and 0.62 in the northern part of the study area. In view of these results, it is suggested that the dominant cause at the spatial and temporal scales are the structure of the rainy season (distribution, concentration) with other causes such as population increase, livestock farming and government planning and their effects in vegetation degradation. Abbreviations: NOAA: National Oceanic and Atmospheric Agency, NDVI: Normalized Difference Vegetation Index, AVHRR: Advanced Very High Resolution Radiometer and MODIS: Moderate Resolution Imaging Spectrometer.
|
