Floristic composition, life forms for C4 species, and the pattern of altitude distribution were studied on Tibetan Plateau. 79 species, in 7 families and 46 genera, were identified with C4 photosynthesis. 95 % of these C4 species belong to Gramineae (51 species), Cyperaceae (14 species), and Chenopodiaceae (10 species), indicating that C4 plants mainly occur in very few families (7 of 204) on the Tibetan Plateau. High altitude distribution for all the Chenopodiaceae C4 species (> 3 000 m above sea level) suggests that plants of this kind have large tolerance to cold, dryness, and strong ultraviolet radiation. Most Gramineae and Cyperaceae C4 species occurrences are consistent with extensive distribution of steppes and meadows in the vast flat of the central Plateau (1 000-3 000 m a.s.l.). Relatively high amount of hemicryptophyte form plants (44 %) in the region indicates that the vegetation, especially grassland, meadows, and steppe, are in good condition. There is a strong relationship between numbers of C4 species and altitude in the Tibetan Plateau. Occurrence of C4 species is significantly less in both high and low altitude plateaux in Tibet. Altitude distribution pattern for C4 species in the region is not only consistent with the altitude and climate, but also with the vegetation types in altitude gradient.
A series of maps showing the level of invasion of the Czech Republic by alien plants was developed based on a quantitative assessment of the level of invasion of 35 terrestrial habitat types at different altitudes. The levels of invasion were quantified for 18,798 vegetation plots, using two measures: proportion of the species that are aliens and total cover of alien species. Separate assessments were made for archaeophytes and neophytes. Within each habitat, the level of invasion was related to altitude using generalized linear models. The level of invasion, depending on the measure used, decreased with altitude in 16 out of 20 habitats for archaeophytes and 18 out of 23 for neophytes. In two habitats, one measure of the level of invasion increased with altitude for archaeophytes. The values of the level of invasion predicted by generalized linear models for particular combinations of habitats and altitudes were projected onto a land-cover map and digital elevation map of the country. Four maps showing the level of invasion were produced, based on the proportion of the species that are archaeophytes or neophytes, and cover of archaeophytes and neophytes. The maps show that both archaeophytes and neophytes are most common in lowland agricultural and urban areas, whereas they are sparsely represented in mountainous areas. At middle altitudes, agricultural areas are more invaded than forested areas. Outside agricultural and urban areas, high levels of invasion are found especially in lowland sandy areas and river corridors.