Main compound of Mongolian ecosystem is natural grassland. Because of increasing effects from humans and animals to the natural grassland, its vegetation cover has been changing considerably. The goal of this paper was to assess climatic and altitudinal effevts on planr species richness and coverage in Mongolian forb-steppe. Vegetation data were collected, using phytosociological methods, from 40 stands in eight areas a crossing approximately 300 km and covering a large proportion of the southeast part of Darkhan-Uul province's area. Mean species number was 18 and 15 in highland and lowland, indicating species number was higher in highland than in lowland (Mann-Whitney U-test, p=0.02). The mean species number was 18 and 16 near to (< 850 m) and far from river (> 2000 m) and it showed insignificance (Mann-Whitney U-test, p=0.23). All sites within highlands showed indifference of species number among years. In lowland, sites which near to river (< 850 m) showed lower species number for year with drought in June (2010), compared to for years with drought in May and normal weather. Species number in highlands was insignificant by years. That in lowlands was lower for year with drought in June than years with drought in May and normal weather. This difference was found in Zeder and Temeen Olom.

communities, vegetation cover, dominant species, species richness

biology

Presentation: oral