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

city (119 mm rainfall, 0.3 °C mean annual temperature and -25.4 °C January mean temperature) are more or less applicable to the Khovd and Myangat samples. The climate of the Bayan Dalay sampling site probably resembles that of the Dalandsadgad (132 mm precipitation, 3.9 °C mean annual temperature and -15.4 °C January mean temperature), at most a little drier and warmer, but one cannot say anything about Bayan Tsagan. It is hard to decide whether the climatic difference (the less evapotranspirational loss because of the same rainfall and lower temperature) or the floristically richer surrounding (Mongol Altai, Khangai and Kharkhira mountains) causes the higher species, family and life-orm richness and diversity, or by chance the nearer groundwater level because of the proximity (less than 20 km) of the Khara Ovs Nor (Blackwater Lake). The effect of the milder environmental conditions is shown both in the higher vegetation cover values and in the higher number of species (18-18). The number of families is similar in the "northern" and "southern" semidesert samples, i. e. the species/family rates are higher. Much more difference exists between the life form spectra: the predominance of the grasses and dwarf shrubs is broken, although their proportion still remains considerable and in the Myangat sample the chamaephyta are replaced by a similar life form, the nanophanerophyta. The dominant grass Stipa glareosa is the same, if ever a species occurring in such a wide range can be genetically the same in such different communities. The apparent hemicryptophyton dominance in the Myangat sample is mostly due to one smallsize, degradation tolerant species, Convolvulus ammannii and to the sampling size problem mentioned above; this species plays much less importance in the community by its abundance and biomass. The degradation (overgrazing) of the Myangat site is indicated by the appearance of some annual weeds as well (Corispermum mongolicum, Salsola pestifera, and Setaria viridis). The Munkh Khairkhan sample shows similar distribution of species and lifeforms, but the floral composition is particular, due to the high mountain character of the site. Even without an arealgeographical analysis one can notice the appearance of some Eurosibirian elements (Rosaceae, Pulsatilla, Poa, Festuca) and the absence of some Central Asian ones (e.g. Chenopodiaceae). This phenomenon is more explicit in the neighbouring subnival tundra and rock vegetation. The extremities of the climate are expressed in the life form composition (chamaephyton-grass dominance again), as well as its relatively more temperate and humid character (9 species of hemicryptophyta). While the Munkh Khairkhan sample can be regarded as an enriched variant of the surrounding lowland semidesert by the infiltration of high mountain glacial relicts, the physiognomically similar Arvaykher sample is undoubtedly an impoverished mountain steppe. The 38 registered species represent a flora almost twice as rich. The first 8-10 dominants and subdominanta are characteristic both of the steppes and the semideserts, and mainly to their transitional zones. This transitional character is shown in the life from spectrum too; the mass of the chamaephyta is still considerable, but most species belong to the hemicryptophyta. The real mid-grass steppes with over 50% vegetation cover and 50-70 species