Abstract: In order to explore the relationship of plant carbon (C) cycling with its habitat in the high-altitude regions, a leguminous shrub, Caragana jubata, that mainly distributed in those areas was studied. We collected leaf and soil samples of C. jubata from 35 sites along an east-west transect across the alpine regions of China. We measured leaf carbon stable isotope (δ¹³C), soil δ¹³C, and the difference between leaf and soil δ¹³C (Δδ¹³C) of each sampling site. We further analyzed the effects of climatic factors, leaf and soil elements on leaf δ¹³C, soil δ¹³C and Δδ¹³C. Results showed that leaf δ¹³C ranged from -30.9‰ to -27.1‰, with a mean value of -28.4‰, soil δ¹³C ranged from -26.2‰ to -23.2‰, with a mean value of -25.3‰, and Δδ¹³C ranged from 2.0‰ to 7.7‰, with a mean value of 3.1‰. δ¹³C values of leaf was significantly lower than that of soil. Soil δ¹³C initially decreased and subsequently increased with increasing leaf δ¹³C. Leaf δ¹³C was negatively correlated with growing season temperature and leaf C content. Soil δ¹³C was negatively correlated with relative humidity and mean temperature of the warmest month, and was positively correlated with soil carbon:nitrogen (C:N). Soil δ¹³C firstly decreased and subsequently increased with soil C content. Δδ¹³C was positively correlated with leaf C content, soil C content, and soil C: N. Climatic factors directly affected leaf δ¹³C and Δδ¹³C, and indirectly affected leaf δ¹³C, soil δ¹³C and Δδ¹³C through their effects on leaf and soil elements. The C cycle of C. jubata was affected by climatic factors, leaf and soil elements in the alpine regions.

Key words: Caragana jubata, carbon stable isotope, climatic factor