L. Hably szerk.: Studia Botanica Hungarica 23. 1992 (Budapest, 1992)

Németh, Ferenc: Vegetation structure studies on steppe and semidesert plant communities of Outer Mongolia 1. Textural relations

are situated in the more humid climatic zone (with about 250 mm or more mean annual precipitation and often with annual mean temperature below zero). The Ulaanbaatar sample represents a site at the periphery of this range, lying near the southern border of the forest steppe zone. It contains many short-grass steppe and semidesert steppe elements. The 53 species belong to 19 families, though some of them can reach such high relative abundance surely by tolerance of overgrazing (e.g. the low, dense cushions forming Entrichum pauciflorum and Androsace vülosa, the poisonous Stellera chamaejasme or the foliose lichens). This sample is the richest in life-forms, and contains a considerable amount of chamaephyta in addition to the dominant grasses (by frequency) and hemicryptophyta (by species number). The Erdenet sample with its 80% vegetation cover, hemicryptophyton-grass overdominance, 60 species and 20 families is a representative of the true forb-rich mid-grass steppes in the midst of the cold-continental forest steppe zone. Grazing is also more moderate than is at Ulaanbaatar. The breakdown in the frequency distribution curve after the six most frequent species may be caused by the insufficient sampling unit number and/or by entering into and unforeseeable "patch" mentioned among the "special perspectives and difficulties". CONCLUSIONS With the classic methods of floral analysis we obtained classic results: the semideserts are poorer in species, overground vegetation cover and moderately rare species (the logarithmic distribution is steeper) than the steppes; the high-mountain variants are influenced mostly by their floral surrounding; the grasses play an important, often determining role in the communities everywhere; the codominants are chamaephyta in the semideserts and hemicryptophyta in the steppes; in the wide transitional climatic range the life-form distribution varies and in general it is more even. Further information can be obtained by approaches from two directions: - distribution analysis from the viewpoints of growth-form, reproductive and dispersal strategies, grazing preferences and (known or supposed) allelopathic effects; - testing the characteristic areas of the species and species combinations by information statistics functions. Acknowledgements: First of all I owe a debt of gratitude to my colleagues, Ms Beáta OBORNY and Mr Ferenc KECSKÉS who suffered all the discomfort of the field work. I am grateful to Dr ULZIYKHUTAG Dr SANCZIR (Botanical Institute of the Academy of Science of MPR, Ulaanbaatar) and Dr Béla JANKÓ (Botanical Department of the Hungarian Natural History Museum, Budapest) for their valuable assistance in taxonomic identification.