THE MOUNTAIN VEGETATION OF SOUTH PERU: SYNTAXONOMY, ECOLOGY, PHYTOGEOGRAPHY AND CONSERVATION This thesis presents an overview and revision of plant communities from xerophytic and mountain landscapes in the dry Andes of South Peru. The revision is based on comparison of the collected vegetation data with other regional and interregional studies. This phytosociologic overview comprises the arid and semi-arid montane vegetation of the province of Arequipa and besides the plant communities of Moquegua from the prepuna between 3470 and 3700 m, the puna between 3750 and 4500 m and the superpuna between 4450 and 4800 m. The Braun-Blanquet approach and multivariate ordination and classification methods have been applied to classify the different plant communities and to study the relation between plant communities and environmental variables, such as altitude, slope degree and exposition, rock and stone cover percentage, manure cover and grazing. Furthermore the results are presented of a phytogeographical analysis of the Andean puna flora (at vascular genus level) and its relation to other tropicalpine regions in South America. Finally, the descriptions of six recently published new species are included in this thesis. The results provide an important database for nature conservation issues, stressing the significance of protecting the fragile and diverse ecosystems of the Moqueguan Andes. The results of this vegetation survey can be used to prioritize the selection and assignment of nature reserves.