A number of cork oak woods in north-eas-tern Algeria are being invaded by maritime pines. These forest dynamics began in the 1980s and although they are often cited as one of the factors of degradation of Algeria's cork oak woods, they have never been researched. The aim of our study, on the cork oak woods of Had-dada (wilaya of El-Tarf) was to identify the determinants of invasion by the maritime pine, Pinus pinaster Ait., by chorological mapping of factors such as slopes, exposure and areas burned by wildfires in 1994, together with mapping of the cork oak woods before and after the invasion. The maps were produced by applying a geomatics approach supplemented by ground surveys. The maps show that the areas invaded by maritime pine are those that were most affected by the fires of 1994, which are also those on steep and very steep slopes. The low resilience of cork oaks, Quercus suber, in such conditions has allowed maritime pines to supplant them. These dynamics are a good illustration of the "patch dynamics" paradigm in Mediterranean forests and also show the invasive potential of maritime pine, which has been shown to be equally invasive elsewhere in the world. The invasion process is likely to be accen-tuated by climate change.
