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  • 1 MTA Centre for Ecological Research Institute of Ecology and Botany H-2163 Vácrátót Hungary
  • 2 MTA-MTM-ELTE Research Group for Palaeontology H-1117 Budapest Hungary
  • 3 University of Debrecen Department of Evolutionary Zoology H-4010 Debrecen Hungary
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In this paper, we elaborated a new concept (the Regularities-Deviations-Uniqueness; RDU framework) to analyse regional vegetation patterns and applied it to the Pannonian region of the Carpathian Basin. We introduced three criteria, namely: distributional regularity, distributional deviation, and compositional uniqueness. Regularities conform to the pattern expected based on macroclimate and relief. Deviations are singular phenomena and are defined as the conspicuous departures from the regular pattern at odds with either zonal pattern (climate rules), or the repetitive extrazonal patterns (relief and meso-climate interactions). Endemic plant communities of the Pannonian region (defined by a unique species composition) are regarded as the unique features. The main regularities recognised for the Pannonian region are: (1) the altitudinal pattern of vegetation belts, (2) the horizontal zonation of the Dunántúl, (3) the gradient of continentality along the mountain ranges, and (4) the circular zonality of the Nagyalföld. Deviations are mostly explained by local vegetation history, mesoclimate, and edaphic factors. The major deviations include (i) occurrence of mixed Pinus sylvestris forests in Őrség, (ii) cool continental forest-steppe forests on Kisalföld, and Gödöllői-dombvidék, (iii) the direct contact of Fagus and Quercus pubescens forests (Bakony, Balatonfelvidék), (iv) the Fraxinus excelsior-Tilia spp. forests on rock outcrops, and (v) the Sphagnum bogs on the Alföld. Individuality of the Pannonian region is demonstrated by the endemic zonal forest-steppe forests and intrazonal endemic communities such as the Cerasus mahaleb-Quercus pubescens forests, and the vegetation on calcareous sand, dolomite and saline soils and the like. We argue that the introduced criteria are suitable for the entitation and description of other biogeographical regions, and offer useful tool for interregional comparisons.

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