C3- and C4-Plants of the Xerophilic Vegetation in the Loess Hills of the Yellow River,Gansu-Province,NW-China*

The climate of the loess-hill area near Lanzhou, on the Yellow River, Gansu-Province, NW-China is arid throughout the year. The vegetation is xerophilic and mainly dominated by species of Zygophyllaceae, Chenopodiaceae, Plumbaginaceae, Tamaricaceae, Asclepiadaceae and Asteraceae. Among 11 species sampled of these families, δ¹³C-analyses only indicated C₄-photosynthesis for 2 species. This relatively low frequency of C₄-plants may be due to elevation (1978 m a.s.l.) and the relatively cold temperatures (annual mean 5.9°C).