Carbon isotope ratios of C_4 plants in loess areas of North China

摘要

Carbon isotope ratios (δ~(13)C) of 89 C_4 plant samples were determined from the loess area in North China. δ~(13)C values vary between -10.5per thousand and -14.6per thousand with a mean of -12.6per thousand. Along a precipitation gradient from the semi-moist area to the semiarid area, then to the arid area, the δ~(13)C values of C_4 plants show a slight decreasing trend. The δ~(13)C values of C_4 plants in the dry season are found lower than those in the wet season. These trends are opposite to those observed for C_3 species.