To understand the effects of leaf physiological and morphological characteristics on δ13C of alpine trees, we examined leaf δ13C value, LA, SD, LNC, LPC, LKC, Chla+b, LDMC, LMA and Narea in one-year-old needles of Picea schrenkiana var. tianschanica at ten points along an altitudinal gradient from 1420 m to 2300 m a.s.l. on the northern slopes of the Tianshan Mountains in northwest China. Our results indicated that all the leaf traits differed significantly among sampling sites along the altitudinal gradient(P<0.001). LA, SD, LPC, LKC increased linearly with increasing elevation, whereas leaf δ13C, LNC, Chla+b, LDMC, LMA and Narea varied non-linearly with changes in altitude. Stepwise multiple regression analyses showed that four controlled physiological and morphological characteristics influenced the variation of δ13C. Among these four controlled factors, LKC was the most profound physiological factor that affected δ13C values, LA was the secondary morphological factor, SD was the third morphological factor, LNC was the last physiological factor. This suggested that leaf δ13C was directly controlled by physiological and morphological adjustments with changing environmental conditions due to the elevation. To understand the effects of leaf physiological and morphological characteristics on δ13C of alpine trees, we examined leaf δ13C value, LA, SD, LNC, LPC, LKC, Chla + b, LDMC, LMA and Narea in one-year-old needles of Picea schrenkiana var. tianschanica at ten points along an altitudinal gradient from 1420 m to 2300 m asl on the northern slopes of the Tianshan Mountains in northwest China. Our results indicates that all the leaf traits difceptible among these sampling sites along the altitudinal gradient (P < 0.001). LA, SD, LPC, LKC increased linearly with increasing elevation, with leaf δ13C, LNC, Chla + b, LDMC, LMA and Narea varied non-linearly with changes in altitude. Stepwise multiple regression analyzes showed that four controlled physiological and morphological characteristics influenced the variation of δ13C. Among these four controlled factors, LKC was the most profound physiological factor that affected δ13C values, LA was the secondary morphological factor, SD was t he third that morphological factor, LNC was the last physiological factor. This suggested that leaf δ13C was directly controlled by physiological and morphological adjustments with changing environmental conditions due to the elevation.