Characters of "traditional" and "modern" vegetation landscapes - a comparison of northern Morocco and southern Spain
The effects of different human impacts on the vegetation cover were studied by comparing southwestern Andalusia and northwestern Morocco. The peninsulas on both sides of the Straits of Gibraltar have almost identical physical conditions but are subjected to different land-use systems. A comparison of the present vegetation of both regions shows how the vegetation cover is transformed by different human societies. The study was carried out in a phytosociological approach at the levels of "plant community" and "catenal vegetation complex". Weed communities vary according to the agro-technical level. Traditional ploughing in self-sustaining agriculture creates agro-phytocoenoses with high alpha-diversity. Agro-industrial management, which prevails in Spain, roughly halves species number per field. The anthropogenic transformation of the weed communities has a similar tendency, with a time lag of some decades in Morocco. In heathland, the anthropo-zoogenic pressure (browsing intensity, fire frequency) is higher in Morocco. This results in mono-dominated stands with low alpha-diversity. The vegetation complexes were studied in two coastal valleys and by comparing the peninsulas as a whole. Every technological level creates specific communities and its own vegetation complex. Character communities for the Spanish or the Moroccan side could be established. We observed intensity vicariants within one land-use type as well as land-use vicariants upon identical physiotopes. Culturally indifferent units are roadside verges and other ruderal communities. Vegetation patterns created by ethnic and cultural traditions are of minor importance, but do exist (Marabut forest, Cañadas). "Modernisation" of vegetation landscapes results in a more trivial plant canopy, monofunctional landunits and a decrease of temporal variation (abandonment of shifting cultivation, disappearance of postcultural succession stages, and oldfield vegetation).