Variations in carbon isotope ratios of C3 plants and distribution of C4 plants along an altitudinal transect on the eastern slope of Mount Gongga

Variations in carbon isotopic ratios (delta C-13) of C-3 plants and distribution of C-4 plants were investigated along an altitudinal transect on the eastern slope of Mount Gongga, and the environmental effects on them were discussed. It is shown that plants with C-4 photosynthetic pathway mainly occur at altitudes below 2100 m a.s.l., suggesting that the low summer temperature is responsible for the distributional pattern. In addition, delta C-13 of C-3 plants increases with elevation at the region above 2000 m a.s.l. with the characteristics of humid climate, and the increase rate in delta C-13 for C-3 plants is about 1.3%. per kilometer. Temperature determines the altitudinal trend of delta C-13.