Quercus suber L. «dehesas» in Sardinia


Abstract: The aim of the present work is to assess the distribution in Sardinia of Quercus suberdehesa through the map of habitat made by using aerial and satellite images. That habitat includesseveral sintaxa of Quercetea ilicis, Cisto-Lavanduleatea, Thero-Brachypodietea, Helianthemeteaguttati classes. The thematic map (1:25,000 scale) was obtained by the following steps:unsupervised classification of satellite images (Landsat TM) and supervised classification byusing the ERDAS software (O.S. Erdas Imagine 8.6, Leica); analysis of combined data fromorthophoto and ground control points in order to verify the supervised map (O.S. Arc Map, ESRI,GPS). The dehesa system typical species of Quercus suber, from 20 to 50% canopy, rises fromagrosilvopastoral practice aimed at extensive livestock, and it is characterized by the scarcity ortotal absence of plant regeneration. They represented the 5% of regional land surface most of allwidespread in the central-northern area and become almost absent in the South. This kind ofgeographic distribution comes from different factors as ecological (climate, geomorphology,geologic and soil) and anthropogene factors (pastures, fires, deforestation, ploughing,overgrazing). The distribution is open to strong changes because the human activity and theenvironment decay that can play a major role in the cork-oak forests, but it is also an importantstage in the wood recovery.

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