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

- The underground part of a plant can be considerably more extensive than its overground organs, as a rule among semidesert shrubs and chamaephyta (MIROSNICHENKO 1975). - The size of the projection of a plant's overground part considerably depends on its construction, that is, on growth form. - The "individual" is often undetectable in the vegetative colonies which are very common both in the semidesert and steppic communities. - The three latter viewpoints and some practical considerations - so as not to obtain too many empty sampling units - made it necessary to apply a quasi-linear sampling instead of the strictly linear, one dimensional method. The width of the "line" equals to the length of the sampling unit (10-50 cm), that is composed by in one dimension adjacent microquadrats. Therefore the presence of a species in the sample represents something between its abundance and the frequency of its individuals, not very much distorting either of them. In the microquadrats only the presence or absence of a species was registered without quantitative estimation. An easier problem is the identification of the unfertile plants. Many of them were grazed down, several others flourish rarely at those extreme climatic conditions, but all of them can be identified at family level, and most of them at the generic level. Their life form, growth and reproductive strategies can be determined without a more precise taxonomic identification. The unclear, polytypic taxa (Agropyron cristatum, Potentilla bifurca, Artemisia frigida, etc.) have been managed in a similar way, however in some cases the life form and growth form differences between the races remained problematic. The role of age structure and the different phenological stages seems to be important, especially in the more complex steppic formations. Such data have been collected, but are not elaborated here. The sampling areas and parameters Therefore I tried to choose sampling areas as similar as possible in their physiognomy, and environmental conditions and as different as possible in their floral composition. For the first requirement I had to work in the same vegetation zones, and for the latter one in places as far from each other as possible. The expected vegetation types were determined from the vegetation map of Mongolia (LAVRENKO 1979), but its scale often is too large (1:1,000,000) for an exact identification. 1. Bayan Tsagan Plain semidesert in a high basin of the Gobi Altai mountains, 15 km south of Bayan Tsagan village (Bayan Khongor district), at cca. 1700 m a. s. 1., debris ground with some sand fraction without developed soil, 6-10% vegetation cover, Stipa glareosa - Ajania achilleoides dominance (according to the vegetation map: brown sandy soil, Stipa glareosa -Anabasis brevifolia -Allium potyrrhizum dominance).