Oak woodland vegetation of Turkey - a first overview based on multivariate statistics

Abstract

Questions Turkey is home to more Quercus species than any other country in the western Palaearctic. To what extent is the taxonomic diversity reflected in compositional diversity of oak woodland vegetation? What are the main compositional gradients, their environmental correlates and associated gradients in species traits? How are the oak woodland types in Turkey distributed? What is their stand structure, ecological range, conservation value and how are they used? Which phytosociological syntaxa are represented? What gaps remain in knowledge of Turkey's oak woodlands that require further study? Location Turkey (SE Europe, SW Asia). Methods We used 1181 vegetation records of oak woodland retrieved from phytosociological literature, sampled at more than 100 sites all over Turkey. We classified the data set using a modified TWINSPAN algorithm and displayed the classification using a dendrogram and a synoptic table. We used detrended correspondence analysis and canonical correspondence analysis to identify main compositional patterns, their environmental correlates and associated gradients in species traits. The phi coefficient was used to identify the diagnostic species of the distinguished vegetation types. Species composition, ecological range, biogeographic affinities, traditional phytosociological treatment and land use of each type were described using standard forms. Results The main gradients in compositional diversity of Turkey's oak woodland vegetation range from xerophytic evergreen woodlands near the Mediterranean Sea coast to mesophytic deciduous forests near the Black Sea coast and to continental open (semi-) deciduous (south-) east Anatolian woodlands and shrublands. These compositional gradients are associated with gradients in species traits and macroclimate. Silvopastoralism and coppicing are very common forms of land use of Turkish oak forests, although both have somewhat declined recently. Old-growth forests are scarce or absent in most oak-dominated systems. Conclusions Compositional diversity of Turkish oak woodland vegetation is extensive and reflects the biogeographical subdivision of the country. However, the ecology of several oak species and their ecosystems is still little known. A major gap in the available data and knowledge lies in east and southeast Anatolia. The currently protected forest area should be revised to cover all the oak woodland types identified in this paper.