Ecology, Environment and Conservation Paper

A 1000-YEAR RECORD FROM EL-GHORRA MOUNTAIN (NE ALGERIA) : MEDITERRANEAN VEGETATION DYNAMIC IN RESPONSE TO CLIMATIC VARIATION

Youbi Mustapha and Benslama Mohamed

Abstract

The work deals with the reconstruction of a part of the vegetation history in Djebel El-Ghorra, a midaltitude mountain located at El-Kala Natural Park in Northeast of Algeria by combining physicchemical analysis with a paleopalynological approach. Thanks to a standard physicochemical analysis as well as to a pollen diagram obtained from the study of a core taken at an altitude of 1003 m which has been supported by three A.M.S. radiocarbon dates, it was possible to get new and valuable information about the dynamic of the local vegetation over the last millennium. At the end of the tenth century A.D., the deciduous oak forest would have undergone a phase of regression due to a local climate aridification coinciding with the Medieval Warm Period while herbaceous taxa dominated the landscape. A major expansion of the deciduous oak woodlands would have started between 750-850 BP lasting up to 200-100 BP corresponding to the final phase of the Medieval Optimum and the Little Ice Age periods. During this phase, the region would have benefited of a rainy and fairly mild climate allowing deciduous oak forests to expand along with Alnus;. the proliferation of the latter is regarded as a strong sign of a wet and humid environment. Thermophilous shrubs like Erica, Cistus as well as a better presence of Quercus ilex-type at the detriment of the deciduous oak is the main feature of the region’s modern era which would have probably started around 200-100 BP, resulting in an increasingly dislocated and scattered deciduous forest leaving the place to mid-altitude maquis dominated by Erica and Cistus. These variations of Mount El-Ghorra mid-altitude vegetation over the last millennium are correlated with major climatic events that have shaped other regions in the Northern Hemisphere as well as in the Mediterranean region.