Carbon isotope ratios (δ 13C) of 89 C4 plant samples were determined from the loess area in North China. δ 13C values vary between –10.5‰ and –14.6‰ with a mean of –12.6‰. Along a pre-cipitation gradient from the semi-moist area to the semiarid area, then to the arid area, the δ 13C val-ues of C4 plants show a slight decreasing trend. The δ 13C values of C4 plants in the dry season are found lower than those in the wet season. These trends are opposite to those observed for C3 spe-cies.
WANG Guoan1,2,3, HAN Jiamao 2, ZHOU Liping3, XIONG Xiaogang4, TAN Ming2, WU Zhenhai5 & PENG Jun6 1. Department of Plant Nutrition, China Agricultural University, Beijing 100094, China
d 13C of 367 C3 herbaceous plants was measured in loess area in northern China. Their d 13C values vary between -21.7 and -30.0, with a mean of -26.7. In the center of Loess Plateau (semimoist area) with annual precipitation of 400─600 mm, the d 13C values of C3 herba-ceous plants range from -24.4 to -28.5, with a mean of -27.5. In the west of Loess Plateau (semiarid and arid area) with annual precipitation less than 400 mm, they range between -21.7 and -30.0, with a mean of -26.2. Annual precipitation is the main factor that makes d 13C val-ues of C3 herbaceous plants in the west greater than those in the central Loess Plateau. The composition of d 13C in C3 plants increases with deceasing annual precipitation, and the mean change is -0.49/100 mm.
