Amri R. auteur aut IRD Zribi Mehrez auteur aut IRD Lili-Chabaane Z. auteur aut IRD Duchemin Benoît auteur aut IRD Gruhier C. auteur aut IRD Chehbouni Abdelghani auteur aut IRD text journalArticle eng text/pdf reformatted digital access The analysis of vegetation dynamics is essential in semi-arid regions, in particular because of the frequent occurrence of long periods of drought. In this paper, multi-temporal series of the Normalized Difference of Vegetation Index (NDVI), derived from SPOT-VEGETATION satellite data between September 1998 and June 2010, were used to analyze the vegetation dynamics over the semi-arid central region of Tunisia. A study of the persistence of three types of vegetation (pastures, annual agriculture and olive trees) is proposed using fractal analysis, in order to gain insight into the stability/instability of vegetation dynamics. In order to estimate the state of vegetation cover stress, we propose evaluating the properties of an index referred to as the Vegetation Anomaly Index (VAI). A positive VAI indicates high vegetation dynamics, whereas a negative VAI indicates the presence of vegetation stress. The VAI is tested for the above three types of vegetation, during the study period from 1998 to 2010, and is compared with other drought indices. The VAI is found to be strongly correlated with precipitation. specialized vegetation SPOT-VEGETATION NDVI index drought persistence Vegetation Drought Index TUNISIE ZONE ARIDE 082 126 3 12 2568-2590 2011 2072-4292 https://www.documentation.ird.fr/hor/fdi:010057126 10.3390/rs3122568 2072-4292 [F B010057126] https://www.documentation.ird.fr/hor/fdi:010057126 https://horizon.documentation.ird.fr/exl-doc/pleins_textes/divers17-09/010057126.pdf IRD - Base Horizon / Pleins textes 2012-10-03 2017-10-03 fdi:010057126 fre